FusionWiki - User contributions [en]

TJ-II: On the electrostatic transport driven by Alfvén modes and broadband turbulence in the plasma edge region of the TJ-II stellarator

2022-01-24T15:06:19Z

Hidalgo: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: On the electrostatic transport driven by Alfvén modes and broadband turbulence in the plasma edge region of the TJ-II stellarator'''

== Name and affiliation of proponent ==

Igor Voldiner, Carlos Hidalgo
Laboratorio Nacional de Fusión, CIEMAT, Madrid, Spain

Hiromi Takahashi / NIFS, Japan

David Zarsoso,
Marseille University, France

 Jacobo Varela,
UC3M, Madrid, Spain

== Details of contact person at LNF ==
Igor Voldiner

== Description of the activity ==

The importance of quasi-coherent modes on transport is a growing area of research due its possible role in the development of reactor relevant scenarios. HIBP measurements have provided direct measurements of core ExB transport induced by AEs in the TJ-II stellarator <ref> A. Melnikov et al., Nucl. Fusion 50, 084023 (2010)</ref>. It was found that the AEs contribution to the frequency resolved turbulent particle transport constitutes a significant fraction of the total flux. Interestingly although most of the AEs contribute to outwards ExB flux some modes produce inward flux.

Recently edge probes measurements that shown that electrostatic turbulence and AEs driven transport are comparable in magnitude. Whereas the turbulent transport keeps always the same radially outwards propagation, AEs can be inwards or outwards depending of the NBI co-counter configuration. In addition, edge biasing is capable to module the amplitude of ExB transport driven by plasma turbulence but has a minor impact on the ExB transport driven by AEs. These results highlight the key role of the cross-phase between density and electric field fluctuations to control the level of ExB driven transport

The goal of this proposal is to expand the present database of ExB turbulent transport driven by AEs.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 2
* Essential diagnostic systems: edge probes (in feasible also HIBP)
* Type of plasmas (heating configuration): NBI co & counter configurations
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: On the electrostatic transport driven by Alfvén modes and broadband turbulence in the plasma edge region of the TJ-II stellarator

2022-01-24T15:00:54Z

Hidalgo: /* Description of the activity */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: On the electrostatic transport driven by Alfvén modes and broadband turbulence in the plasma edge region of the TJ-II stellarator'''

== Name and affiliation of proponent ==

Igor Voldiner, Carlos Hidalgo
Laboratorio Nacional de Fusión, CIEMAT, Madrid, Spain

David Zarsoso,
Marseille University, France

 Jacobo Varela,
UC3M, Madrid, Spain

== Details of contact person at LNF ==
Igor Voldiner

== Description of the activity ==

The importance of quasi-coherent modes on transport is a growing area of research due its possible role in the development of reactor relevant scenarios. HIBP measurements have provided direct measurements of core ExB transport induced by AEs in the TJ-II stellarator <ref> A. Melnikov et al., Nucl. Fusion 50, 084023 (2010)</ref>. It was found that the AEs contribution to the frequency resolved turbulent particle transport constitutes a significant fraction of the total flux. Interestingly although most of the AEs contribute to outwards ExB flux some modes produce inward flux.

Recently edge probes measurements that shown that electrostatic turbulence and AEs driven transport are comparable in magnitude. Whereas the turbulent transport keeps always the same radially outwards propagation, AEs can be inwards or outwards depending of the NBI co-counter configuration. In addition, edge biasing is capable to module the amplitude of ExB transport driven by plasma turbulence but has a minor impact on the ExB transport driven by AEs. These results highlight the key role of the cross-phase between density and electric field fluctuations to control the level of ExB driven transport

The goal of this proposal is to expand the present database of ExB turbulent transport driven by AEs.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 2
* Essential diagnostic systems: edge probes (in feasible also HIBP)
* Type of plasmas (heating configuration): NBI co & counter configurations
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: On the electrostatic transport driven by Alfvén modes and broadband turbulence in the plasma edge region of the TJ-II stellarator

2022-01-24T15:00:16Z

Hidalgo: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: On the electrostatic transport driven by Alfvén modes and broadband turbulence in the plasma edge region of the TJ-II stellarator'''

== Name and affiliation of proponent ==

Igor Voldiner, Carlos Hidalgo
Laboratorio Nacional de Fusión, CIEMAT, Madrid, Spain

David Zarsoso,
Marseille University, France

 Jacobo Varela,
UC3M, Madrid, Spain

== Details of contact person at LNF ==
Igor Voldiner

== Description of the activity ==

The importance of quasi-coherent modes on transport is a growing area of research due its possible role in the development of reactor relevant scenarios. HIBP measurements have provided direct measurements of core ExB transport induced by AEs in the TJ-II stellarator <ref> A. Melnikov et al., Nucl. Fusion 50, 084023 (2010)</ref>. It was found that the AEs contribution to the frequency resolved turbulent particle transport constitutes a significant fraction of the total flux. Interestingly although most of the AEs contribute to outwards ExB flux some modes produce inward flux.

Recently edge probes measurements have shown that shown that electrostatic turbulence and AEs driven transport are comparable in magnitude. Whereas the turbulent transport keeps always the same radially outwards propagation, AEs can be inwards or outwards depending of the NBI co-counter configuration. In addition, edge biasing is capable to module the amplitude of ExB transport driven by plasma turbulence but has a minor impact on the ExB transport driven by AEs. These results highlight the key role of the cross-phase between density and electric field fluctuations to control the level of ExB driven transport

The goal of this proposal is to expand the present database of ExB turbulent transport driven by AEs.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 2
* Essential diagnostic systems: edge probes (in feasible also HIBP)
* Type of plasmas (heating configuration): NBI co & counter configurations
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: On the electrostatic transport driven by Alfvén modes and broadband turbulence in the plasma edge region of the TJ-II stellarator

2022-01-24T14:59:21Z

Hidalgo: /* Description of required resources */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: On the electrostatic transport driven by Alfvén modes and broadband turbulence in the plasma edge region of the TJ-II stellarator'''

== Name and affiliation of proponent ==
Enter name, affiliation and ORCID code here
Igor Voldiner, Carlos Hidalgo
Laboratorio Nacional de Fusión, CIEMAT, Madrid, Spain

David Zarsoso,
Marseille University, France

 Jacobo Varela,
UC3M, Madrid, Spain

== Details of contact person at LNF ==
Igor Voldiner

== Description of the activity ==

The importance of quasi-coherent modes on transport is a growing area of research due its possible role in the development of reactor relevant scenarios. HIBP measurements have provided direct measurements of core ExB transport induced by AEs in the TJ-II stellarator <ref> A. Melnikov et al., Nucl. Fusion 50, 084023 (2010)</ref>. It was found that the AEs contribution to the frequency resolved turbulent particle transport constitutes a significant fraction of the total flux. Interestingly although most of the AEs contribute to outwards ExB flux some modes produce inward flux.

Recently edge probes measurements have shown that shown that electrostatic turbulence and AEs driven transport are comparable in magnitude. Whereas the turbulent transport keeps always the same radially outwards propagation, AEs can be inwards or outwards depending of the NBI co-counter configuration. In addition, edge biasing is capable to module the amplitude of ExB transport driven by plasma turbulence but has a minor impact on the ExB transport driven by AEs. These results highlight the key role of the cross-phase between density and electric field fluctuations to control the level of ExB driven transport

The goal of this proposal is to expand the present database of ExB turbulent transport driven by AEs.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 2
* Essential diagnostic systems: edge probes (in feasible also HIBP)
* Type of plasmas (heating configuration): NBI co & counter configurations
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: On the electrostatic transport driven by Alfvén modes and broadband turbulence in the plasma edge region of the TJ-II stellarator

2022-01-24T14:58:32Z

Hidalgo: /* Description of the activity */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: On the electrostatic transport driven by Alfvén modes and broadband turbulence in the plasma edge region of the TJ-II stellarator'''

== Name and affiliation of proponent ==
Enter name, affiliation and ORCID code here
Igor Voldiner, Carlos Hidalgo
Laboratorio Nacional de Fusión, CIEMAT, Madrid, Spain

David Zarsoso,
Marseille University, France

 Jacobo Varela,
UC3M, Madrid, Spain

== Details of contact person at LNF ==
Igor Voldiner

== Description of the activity ==

The importance of quasi-coherent modes on transport is a growing area of research due its possible role in the development of reactor relevant scenarios. HIBP measurements have provided direct measurements of core ExB transport induced by AEs in the TJ-II stellarator <ref> A. Melnikov et al., Nucl. Fusion 50, 084023 (2010)</ref>. It was found that the AEs contribution to the frequency resolved turbulent particle transport constitutes a significant fraction of the total flux. Interestingly although most of the AEs contribute to outwards ExB flux some modes produce inward flux.

Recently edge probes measurements have shown that shown that electrostatic turbulence and AEs driven transport are comparable in magnitude. Whereas the turbulent transport keeps always the same radially outwards propagation, AEs can be inwards or outwards depending of the NBI co-counter configuration. In addition, edge biasing is capable to module the amplitude of ExB transport driven by plasma turbulence but has a minor impact on the ExB transport driven by AEs. These results highlight the key role of the cross-phase between density and electric field fluctuations to control the level of ExB driven transport

The goal of this proposal is to expand the present database of ExB turbulent transport driven by AEs.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
* Essential diagnostic systems:
* Type of plasmas (heating configuration):
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: On the electrostatic transport driven by Alfvén modes and broadband turbulence in the plasma edge region of the TJ-II stellarator

2022-01-24T14:58:17Z

Hidalgo: /* Details of contact person at LNF */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: On the electrostatic transport driven by Alfvén modes and broadband turbulence in the plasma edge region of the TJ-II stellarator'''

== Name and affiliation of proponent ==
Enter name, affiliation and ORCID code here
Igor Voldiner, Carlos Hidalgo
Laboratorio Nacional de Fusión, CIEMAT, Madrid, Spain

David Zarsoso,
Marseille University, France

 Jacobo Varela,
UC3M, Madrid, Spain

== Details of contact person at LNF ==
Igor Voldiner

== Description of the activity ==
Enter description here <ref>A. Einstein, Journal of Exceptional Results (2017)</ref>, including motivation/objectives and experience of the proponent (typically one-two pages)

The importance of quasi-coherent modes on transport is a growing area of research due its possible role in the development of reactor relevant scenarios. HIBP measurements have provided direct measurements of core ExB transport induced by AEs in the TJ-II stellarator <ref> A. Melnikov et al., Nucl. Fusion 50, 084023 (2010)</ref>. It was found that the AEs contribution to the frequency resolved turbulent particle transport constitutes a significant fraction of the total flux. Interestingly although most of the AEs contribute to outwards ExB flux some modes produce inward flux.

Recently edge probes measurements have shown that shown that electrostatic turbulence and AEs driven transport are comparable in magnitude. Whereas the turbulent transport keeps always the same radially outwards propagation, AEs can be inwards or outwards depending of the NBI co-counter configuration. In addition, edge biasing is capable to module the amplitude of ExB transport driven by plasma turbulence but has a minor impact on the ExB transport driven by AEs. These results highlight the key role of the cross-phase between density and electric field fluctuations to control the level of ExB driven transport

The goal of this proposal is to expand the present database of ExB turbulent transport driven by AEs.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
* Essential diagnostic systems:
* Type of plasmas (heating configuration):
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: On the electrostatic transport driven by Alfvén modes and broadband turbulence in the plasma edge region of the TJ-II stellarator

2022-01-24T14:58:00Z

Hidalgo: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: On the electrostatic transport driven by Alfvén modes and broadband turbulence in the plasma edge region of the TJ-II stellarator'''

== Name and affiliation of proponent ==
Enter name, affiliation and ORCID code here
Igor Voldiner, Carlos Hidalgo
Laboratorio Nacional de Fusión, CIEMAT, Madrid, Spain

David Zarsoso,
Marseille University, France

 Jacobo Varela,
UC3M, Madrid, Spain

== Details of contact person at LNF ==
If applicable, enter contact person here or write N/A

== Description of the activity ==
Enter description here <ref>A. Einstein, Journal of Exceptional Results (2017)</ref>, including motivation/objectives and experience of the proponent (typically one-two pages)

The importance of quasi-coherent modes on transport is a growing area of research due its possible role in the development of reactor relevant scenarios. HIBP measurements have provided direct measurements of core ExB transport induced by AEs in the TJ-II stellarator <ref> A. Melnikov et al., Nucl. Fusion 50, 084023 (2010)</ref>. It was found that the AEs contribution to the frequency resolved turbulent particle transport constitutes a significant fraction of the total flux. Interestingly although most of the AEs contribute to outwards ExB flux some modes produce inward flux.

Recently edge probes measurements have shown that shown that electrostatic turbulence and AEs driven transport are comparable in magnitude. Whereas the turbulent transport keeps always the same radially outwards propagation, AEs can be inwards or outwards depending of the NBI co-counter configuration. In addition, edge biasing is capable to module the amplitude of ExB transport driven by plasma turbulence but has a minor impact on the ExB transport driven by AEs. These results highlight the key role of the cross-phase between density and electric field fluctuations to control the level of ExB driven transport

The goal of this proposal is to expand the present database of ExB turbulent transport driven by AEs.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
* Essential diagnostic systems:
* Type of plasmas (heating configuration):
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: On the electrostatic transport driven by Alfvén modes and broadband turbulence in the plasma edge region of the TJ-II stellarator

2022-01-24T14:57:39Z

Hidalgo: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: On the electrostatic transport driven by Alfvén modes and broadband turbulence in the plasma edge region of the TJ-II stellarator'''

== Name and affiliation of proponent ==
Enter name, affiliation and ORCID code here
Igor Voldines, Carlos Hidalgo
Laboratorio Nacional de Fusión, CIEMAT, Madrid, Spain

David Zarsoso,
Marseille University, France

 Jacobo Varela,
UC3M, Madrid, Spain

== Details of contact person at LNF ==
If applicable, enter contact person here or write N/A

== Description of the activity ==
Enter description here <ref>A. Einstein, Journal of Exceptional Results (2017)</ref>, including motivation/objectives and experience of the proponent (typically one-two pages)

The importance of quasi-coherent modes on transport is a growing area of research due its possible role in the development of reactor relevant scenarios. HIBP measurements have provided direct measurements of core ExB transport induced by AEs in the TJ-II stellarator <ref> A. Melnikov et al., Nucl. Fusion 50, 084023 (2010)</ref>. It was found that the AEs contribution to the frequency resolved turbulent particle transport constitutes a significant fraction of the total flux. Interestingly although most of the AEs contribute to outwards ExB flux some modes produce inward flux.

Recently edge probes measurements have shown that shown that electrostatic turbulence and AEs driven transport are comparable in magnitude. Whereas the turbulent transport keeps always the same radially outwards propagation, AEs can be inwards or outwards depending of the NBI co-counter configuration. In addition, edge biasing is capable to module the amplitude of ExB transport driven by plasma turbulence but has a minor impact on the ExB transport driven by AEs. These results highlight the key role of the cross-phase between density and electric field fluctuations to control the level of ExB driven transport

The goal of this proposal is to expand the present database of ExB turbulent transport driven by AEs.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
* Essential diagnostic systems:
* Type of plasmas (heating configuration):
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: On the electrostatic transport driven by Alfvén modes and broadband turbulence in the plasma edge region of the TJ-II stellarator

2022-01-24T14:56:25Z

Hidalgo: /* Description of the activity */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: On the electrostatic transport driven by Alfvén modes and broadband turbulence in the plasma edge region of the TJ-II stellarator'''

== Name and affiliation of proponent ==
Enter name, affiliation and ORCID code here

Suggested format:

[https://orcid.org/0000-0000-0000-0000 John Doe], University of Ivory Tower

== Details of contact person at LNF ==
If applicable, enter contact person here or write N/A

== Description of the activity ==
Enter description here <ref>A. Einstein, Journal of Exceptional Results (2017)</ref>, including motivation/objectives and experience of the proponent (typically one-two pages)

The importance of quasi-coherent modes on transport is a growing area of research due its possible role in the development of reactor relevant scenarios. HIBP measurements have provided direct measurements of core ExB transport induced by AEs in the TJ-II stellarator <ref> A. Melnikov et al., Nucl. Fusion 50, 084023 (2010)</ref>. It was found that the AEs contribution to the frequency resolved turbulent particle transport constitutes a significant fraction of the total flux. Interestingly although most of the AEs contribute to outwards ExB flux some modes produce inward flux.

Recently edge probes measurements have shown that shown that electrostatic turbulence and AEs driven transport are comparable in magnitude. Whereas the turbulent transport keeps always the same radially outwards propagation, AEs can be inwards or outwards depending of the NBI co-counter configuration. In addition, edge biasing is capable to module the amplitude of ExB transport driven by plasma turbulence but has a minor impact on the ExB transport driven by AEs. These results highlight the key role of the cross-phase between density and electric field fluctuations to control the level of ExB driven transport

The goal of this proposal is to expand the present database of ExB turbulent transport driven by AEs.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
* Essential diagnostic systems:
* Type of plasmas (heating configuration):
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: On the electrostatic transport driven by Alfvén modes and broadband turbulence in the plasma edge region of the TJ-II stellarator

2022-01-24T14:54:07Z

Hidalgo: Created page with "== Experimental campaign == Spring 2022 == Proposal title == '''TJ-II: On the electrostatic transport driven by Alfvén modes and broadband turbulence in the plasma edge regi..."

TJ-II: On the search of Zonal Flows and the influence of Alfvén Eigenmodes in the TJ-II stellarator

2022-01-21T15:59:34Z

Hidalgo: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: On the search of core Zonal Flows and the influence of Alfvén Eigenmodes in the TJ-II stellarator'''

== Name and affiliation of proponent ==
A. Melnikov, G. Sarancha, M. Drabinskiy and the HIBP Kurchatov Institute team, Russia;

A. Kozachek and the HIBP Kharkov Institute team, Ukrania;

D. Zarzoso, Marseille University, France;

J. Varela, Carlos III University, Spain

Ciemat team

== Details of contact person at LNF ==
Arturo Alonso, Carlos Hidalgo

== Description of the activity ==

While most previous research efforts have been focussed on the excitation and impact of fast ions modes in plasma performance, because of the drain of energy related to fast particle losses with concomitant potential damages in the plasma facing components, there is a growing interest on the impact of fast particles on plasma turbulence and self-organization phenomena. Nonlinear electromagnetic stabilization by suprathermal pressure gradients has been found in gyrokinetic (GK) simulations providing an interpretation of the experimentally observed ion heat flux and stiffness reduction in the JET tokamak <ref> CITRIN, J. et al., Nonlinear Stabilization of Tokamak Microturbulence by Fast Ions, Phys. Rev. Lett 111, 155001(2013)</ref>. Understanding the underlying physics of this non-linear electromagnetic stabilization mechanism is an essential task for future fusion reactors where plasmas will be dominated by fast particle dynamics. The coexistence and interplay of fast ions with main instabilities such as ITG and TEM is an active area of research []. In particular, non-linear excitations of zonal structures by fast particle driven modes have been predicted but validation is still missing <ref> HIDALGO, C. et al., Overview of the TJ-II stellarator research programme towards model validation in fusion plasmas, Nuclear Fusion (2021) </ref>. The plasma scenarios where fast particle driven zonal structures would affect the nonlinear dynamics of AEs or / and turbulent transport is at present an active area of research.

The main focus of this work is the experimental search of zonal flows and the possible influence of fast particle driven modes in the dynamics of zonal flows in the plasma core region of fusion plasmas. In this study both HIBP-I and HIBP-II systems will operate in scanning and fixed point mode to determine plasma profiles as well as plasma potential and density fluctuations in an specific radial location. This unique set-up permits the simultaneous investigation of the radial structure of fluctuations and long-range correlated scales in the whole plasma poloidal cross-section in the TJ-II stellarator.

== International or National funding project or entity ==
Eurofusion (Kharkov team)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 2
* Essential diagnostic systems: Dual HIBP
* Type of plasmas (heating configuration): NBI co & counter
* Specific requirements on wall conditioning if any: Li coating
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: May - June 2022



== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II:L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflectometry and HIBP diagnostics

2022-01-21T15:40:34Z

Hidalgo: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflectometry and HIBP diagnostics'''

== Name and affiliation of proponent ==
L. Eliseev and the HIBP Kurchatov team, Russia

A. Kozachek and the HIBP Kharkov team, Ukraine

M. Koepke UWV, USA

T. Estrada, E. de la Cal, I. Voldiner, M.A. Ochando, CIEMAT

== Details of contact person at LNF ==
Teresa Estrada

https://orcid.org/0000-0001-6205-2656

== Description of the activity ==
At TJ-II, spontaneous L-H transitions are achieved in neutral beam injection (NBI) heated plasma. Abrupt as well as gradual transitions are achieved depending, among other plasma parameters, on the heating power and magnetic configuration topology. Doppler reflectometry (DR) measurements show an increase in the negative radial electric field (Er) together with a reduction in plasma turbulence at the transition [1]. These measurements together with measurements obtained using a dual Langmuir probe system [2] indicate that the trigger of the L-H transition is more correlated with the development of fluctuating radial electric fields than steady-state Er effects. This conclusion is further stressed when operating close to the L-H transition threshold conditions, where pronounced oscillations in both, Er and density turbulence measured by DR show a characteristic predator-prey relation [3]. These experimental observations are consistent with L-H transition models based on turbulence-induced sheared/zonal flows. In addition, HIBP measurements show a reduction in the plasma turbulence and associated flux not only in the plasma edge region but also in the plasma core [4].
Recently a Gas Puff Imaging system (GPI) has been installed and tested at TJ-II. The new gas injection system is used with a camera system that allows 3 simultaneous filtered frames to apply the He I ratio technique, getting 2D measurements of the edge plasma electron density ne and temperature Te with spatial resolution of 3 mm and temporal resolution down to 10 microseconds [5]. This new diagnostic will permit the 2-D characterization of edge and SOL plasma turbulence and is expected to provide additional valuable information on the behaviour of the turbulence during the L-H transition.
The whole set of diagnostics operating simultaneously will allow the characterization of the plasma turbulence evolution from the SOL (GPI and probes) to the plasma gradient (DR) and plasma core (HIBP) regions at the L-H transition.

[1] T. Estrada et al., Plasma Phys. Control. Fusion 51, 124015 (2009)

[2] C. Hidalgo et al., EPL 87, 55002 (2009)

[3] T. Estrada et al., Phys. Rev. Lett. 107, 245004 (2011) 

[4] A. Melnikov et al., Nucl. Fusion 53, 092002 (2013)

[5] E. de la Cal and TJ-II Team, Nucl. Fusion 56, 106031 (2016)

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
Experiments in March 2022 focussed on GPI & DR: To prepare the experiment we need first to reproduce the conditions for L-H transitions. Once the proper conditions are found, He puffing will be introduced for GPI measurements.

Experiments in May 2022 focussed on HIBP & DR & Probes

Experiments in June 2022 focussed on simultaneous measurements using the whole set of TJ-II diagnostics

* Essential diagnostic systems: GPI, Doppler reflectometer, Langmuir probes, HIBP, microwave interferometer, Thomson scattering, Hα detectors, diamagnetic, Rogosky and Mirnov coils, SXR, bolometry

* Type of plasmas (heating configuration): NBI plasmas with plasma target created by ECH in the standard (or 101_42_64) magnetic configuration.

* Specific requirements on wall conditioning if any: Fresh Li is required for a good density control during the NBI phase.

* External users: need a local computer account for data access: no

* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: experiments splitted in three blocks in March (DR and GPI), May and June (availability of HIBP)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II:L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflectometry and HIBP diagnostics

2022-01-21T15:40:22Z

Hidalgo: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''L-H transition studies: characterization of plasma turbulence using Gas Puff Imaging, Probes, Doppler reflectometry and HIBP diagnostics'''

== Name and affiliation of proponent ==
Leonid Eliseev and the HIBP Kurchatov team, Russia

A. Kozachek and the HIBP Kharkov team, Ukraine

M. Koepke UWV, USA

T. Estrada, E. de la Cal, I. Voldiner, M.A. Ochando, CIEMAT

== Details of contact person at LNF ==
Teresa Estrada

https://orcid.org/0000-0001-6205-2656

== Description of the activity ==
At TJ-II, spontaneous L-H transitions are achieved in neutral beam injection (NBI) heated plasma. Abrupt as well as gradual transitions are achieved depending, among other plasma parameters, on the heating power and magnetic configuration topology. Doppler reflectometry (DR) measurements show an increase in the negative radial electric field (Er) together with a reduction in plasma turbulence at the transition [1]. These measurements together with measurements obtained using a dual Langmuir probe system [2] indicate that the trigger of the L-H transition is more correlated with the development of fluctuating radial electric fields than steady-state Er effects. This conclusion is further stressed when operating close to the L-H transition threshold conditions, where pronounced oscillations in both, Er and density turbulence measured by DR show a characteristic predator-prey relation [3]. These experimental observations are consistent with L-H transition models based on turbulence-induced sheared/zonal flows. In addition, HIBP measurements show a reduction in the plasma turbulence and associated flux not only in the plasma edge region but also in the plasma core [4].
Recently a Gas Puff Imaging system (GPI) has been installed and tested at TJ-II. The new gas injection system is used with a camera system that allows 3 simultaneous filtered frames to apply the He I ratio technique, getting 2D measurements of the edge plasma electron density ne and temperature Te with spatial resolution of 3 mm and temporal resolution down to 10 microseconds [5]. This new diagnostic will permit the 2-D characterization of edge and SOL plasma turbulence and is expected to provide additional valuable information on the behaviour of the turbulence during the L-H transition.
The whole set of diagnostics operating simultaneously will allow the characterization of the plasma turbulence evolution from the SOL (GPI and probes) to the plasma gradient (DR) and plasma core (HIBP) regions at the L-H transition.

[1] T. Estrada et al., Plasma Phys. Control. Fusion 51, 124015 (2009)

[2] C. Hidalgo et al., EPL 87, 55002 (2009)

[3] T. Estrada et al., Phys. Rev. Lett. 107, 245004 (2011) 

[4] A. Melnikov et al., Nucl. Fusion 53, 092002 (2013)

[5] E. de la Cal and TJ-II Team, Nucl. Fusion 56, 106031 (2016)

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
Experiments in March 2022 focussed on GPI & DR: To prepare the experiment we need first to reproduce the conditions for L-H transitions. Once the proper conditions are found, He puffing will be introduced for GPI measurements.

Experiments in May 2022 focussed on HIBP & DR & Probes

Experiments in June 2022 focussed on simultaneous measurements using the whole set of TJ-II diagnostics

* Essential diagnostic systems: GPI, Doppler reflectometer, Langmuir probes, HIBP, microwave interferometer, Thomson scattering, Hα detectors, diamagnetic, Rogosky and Mirnov coils, SXR, bolometry

* Type of plasmas (heating configuration): NBI plasmas with plasma target created by ECH in the standard (or 101_42_64) magnetic configuration.

* Specific requirements on wall conditioning if any: Fresh Li is required for a good density control during the NBI phase.

* External users: need a local computer account for data access: no

* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: experiments splitted in three blocks in March (DR and GPI), May and June (availability of HIBP)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: Combining retarding-field energy analyzer and electrostatic probes measurements, an approach to measure the phase relation between density and temperature fluctuations using RFA?

2022-01-21T15:38:27Z

Hidalgo: /* Description of the activity */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''Combining retarding-field energy analyzer and electrostatic probes measurements, an approach to measure the phase relation between density and temperature fluctuations using RFA?'''

== Name and affiliation of proponent ==
Igor Nedzelskiy, Carlos Silva (IST)

Mark Koepke (UWV)

Igor Voldiner, Daniel Carralero, Gregorio Martin, J. L. de Pablos, Carlos Hidalgo (CIEMAT)

HIBP Kurchatov team, Russia

HIBP Kharkov team, Ukraine

== Details of contact person at LNF ==
Igor Voldiner

== Description of the activity ==
'''Rational'''. Why is there decoupling between particle and energy transport channels at the transition to improved confinement regimes?. Physics behind uncoupled transport channels is a relevant open question for understanding both ELM control techniques (e.g. using RMP) as part of the ITER base-line scenario and the development of plasma scenarios without ELMs (e.g. I-mode). Interestingly, uncoupled transport channels has been also reported in stellarators. Transport channel decoupling could be driven by any mechanism that leads to a modification of the cross-phase between density and temperature fluctuations caused by changing driving conditions..
The retarding-field energy analyzer (RFA) is a widely used diagnostic tool for ion temperature measurement in the confined-plasma outer boundary. However, temporal resolution in the standard RFA application is restricted to the milliseconds timescale. A new technique has been developed which allows for the measurement of the plasma ion temperature fluctuations <ref>I. Nedzelskiy et al., Rev. Sci. Instrum. 82 (2011) 043505</ref>. The method is based on measurements of two points on the exponentially decaying region of the I–V characteristic with two differently dc-biased RFEA electrodes. Integrating RFA with electrostatic probes would allow measuring temperature and density fluctuations simultaneously and without phase shift effects.

'''Goal'''. We propose to explore the feasibility of measuring the phase relation between density and temperature fluctuations using a combined diagnostic based on Retarting Field Analyzer (RFA) and Langmuir probes that has been recently developed in the TJ-II stellarator.

In addition, the unique capabilities of the dual HIBP system would allow the investigation of density and potential fluctuations in the TJ-II stellarator, from plasma core to plasma edge. Simultaneous, spatially overlapping, measurement of plasma parameters, using HIBP and electrostatic probes, would allow novel probe configurations [i.e. baffled probes <ref>V.I. Demidov et al., Contrib. Plasma Phys. 44 (2004) 689</ref>] to be tested, and would provide plasma boundary conditions for HIBP calibration.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 2
* Essential diagnostic systems: RFA, Probes. HIBP operation is also highly desirable.
* Type of plasmas (heating configuration): ECRH with density ramp-up and ramp-down to include electron-ion root transitions
* Specific requirements on wall conditioning if any: no
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: Combining retarding-field energy analyzer and electrostatic probes measurements, an approach to measure the phase relation between density and temperature fluctuations using RFA?

2022-01-21T15:36:38Z

Hidalgo: /* Description of required resources */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''Combining retarding-field energy analyzer and electrostatic probes measurements, an approach to measure the phase relation between density and temperature fluctuations using RFA?'''

== Name and affiliation of proponent ==
Igor Nedzelskiy, Carlos Silva (IST)

Mark Koepke (UWV)

Igor Voldiner, Daniel Carralero, Gregorio Martin, J. L. de Pablos, Carlos Hidalgo (CIEMAT)

HIBP Kurchatov team, Russia

HIBP Kharkov team, Ukraine

== Details of contact person at LNF ==
Igor Voldiner

== Description of the activity ==
'''Rational'''. Why is there decoupling between particle and energy transport channels at the transition to improved confinement regimes?. Physics behind uncoupled transport channels is a relevant open question for understanding both ELM control techniques (e.g. using RMP) as part of the ITER base-line scenario and the development of plasma scenarios without ELMs (e.g. I-mode). Interestingly, uncoupled transport channels has been also reported in stellarators. Transport channel decoupling could be driven by any mechanism that leads to a modification of the cross-phase between density and temperature fluctuations caused by changing driving conditions..
The retarding-field energy analyzer (RFA) is a widely used diagnostic tool for ion temperature measurement in the confined-plasma outer boundary. However, temporal resolution in the standard RFA application is restricted to the milliseconds timescale. A new technique has been developed which allows for the measurement of the plasma ion temperature fluctuations <ref>I. Nedzelskiy et al., Rev. Sci. Instrum. 82 (2011) 043505</ref>. The method is based on measurements of two points on the exponentially decaying region of the I–V characteristic with two differently dc-biased RFEA electrodes. Integrating RFA with electrostatic probes would allow measuring temperature and density fluctuations simultaneously and without phase shift effects.

'''Goal'''. We propose to explore the feasibility of measuring the phase relation between density and temperature fluctuations using a combined diagnostic based on Retarting Field Analyzer (RFA) and Langmuir probes that has been recently developed in the TJ-II stellarator.

In addition, the unique capabilities of the dual HIBP system would allow the investigation of density and potential fluctuations in the TJ-II stellarator, from plasma core to plasma edge. Simultaneous, spatially overlapping, measurement of plasma parameters, using HIBP and electrostatic probes, would allow novel probe configurations [e.g. baffled probes] to be tested, and would provide plasma boundary conditions for HIBP calibration.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 2
* Essential diagnostic systems: RFA, Probes. HIBP operation is also highly desirable.
* Type of plasmas (heating configuration): ECRH with density ramp-up and ramp-down to include electron-ion root transitions
* Specific requirements on wall conditioning if any: no
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: Combining retarding-field energy analyzer and electrostatic probes measurements, an approach to measure the phase relation between density and temperature fluctuations using RFA?

2022-01-21T15:34:38Z

Hidalgo: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''Combining retarding-field energy analyzer and electrostatic probes measurements, an approach to measure the phase relation between density and temperature fluctuations using RFA?'''

== Name and affiliation of proponent ==
Igor Nedzelskiy, Carlos Silva (IST)

Mark Koepke (UWV)

Igor Voldiner, Daniel Carralero, Gregorio Martin, J. L. de Pablos, Carlos Hidalgo (CIEMAT)

HIBP Kurchatov team, Russia

HIBP Kharkov team, Ukraine

== Details of contact person at LNF ==
Igor Voldiner

== Description of the activity ==
'''Rational'''. Why is there decoupling between particle and energy transport channels at the transition to improved confinement regimes?. Physics behind uncoupled transport channels is a relevant open question for understanding both ELM control techniques (e.g. using RMP) as part of the ITER base-line scenario and the development of plasma scenarios without ELMs (e.g. I-mode). Interestingly, uncoupled transport channels has been also reported in stellarators. Transport channel decoupling could be driven by any mechanism that leads to a modification of the cross-phase between density and temperature fluctuations caused by changing driving conditions..
The retarding-field energy analyzer (RFA) is a widely used diagnostic tool for ion temperature measurement in the confined-plasma outer boundary. However, temporal resolution in the standard RFA application is restricted to the milliseconds timescale. A new technique has been developed which allows for the measurement of the plasma ion temperature fluctuations <ref>I. Nedzelskiy et al., Rev. Sci. Instrum. 82 (2011) 043505</ref>. The method is based on measurements of two points on the exponentially decaying region of the I–V characteristic with two differently dc-biased RFEA electrodes. Integrating RFA with electrostatic probes would allow measuring temperature and density fluctuations simultaneously and without phase shift effects.

'''Goal'''. We propose to explore the feasibility of measuring the phase relation between density and temperature fluctuations using a combined diagnostic based on Retarting Field Analyzer (RFA) and Langmuir probes that has been recently developed in the TJ-II stellarator.

In addition, the unique capabilities of the dual HIBP system would allow the investigation of density and potential fluctuations in the TJ-II stellarator, from plasma core to plasma edge. Simultaneous, spatially overlapping, measurement of plasma parameters, using HIBP and electrostatic probes, would allow novel probe configurations [e.g. baffled probes] to be tested, and would provide plasma boundary conditions for HIBP calibration.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 1
* Essential diagnostic systems: RFA, Probes
* Type of plasmas (heating configuration): ECRH with density ramp-up and ramp-down to include electron-ion root transitions
* Specific requirements on wall conditioning if any: no
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: Combining retarding-field energy analyzer and electrostatic probes measurements, an approach to measure the phase relation between density and temperature fluctuations using RFA?

2022-01-21T15:33:52Z

Hidalgo: /* Description of the activity */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''Combining retarding-field energy analyzer and electrostatic probes measurements, an approach to measure the phase relation between density and temperature fluctuations using RFA?'''

== Name and affiliation of proponent ==
Igor Nedzelskiy, Carlos Silva (IST)

Mark Koepke (UWV)

Igor Voldiner, Daniel Carralero, Gregorio Martin, J. L. de Pablos, Carlos Hidalgo (CIEMAT)

HIBP Kurchatov and Kharkov team

== Details of contact person at LNF ==
Igor Voldiner

== Description of the activity ==
'''Rational'''. Why is there decoupling between particle and energy transport channels at the transition to improved confinement regimes?. Physics behind uncoupled transport channels is a relevant open question for understanding both ELM control techniques (e.g. using RMP) as part of the ITER base-line scenario and the development of plasma scenarios without ELMs (e.g. I-mode). Interestingly, uncoupled transport channels has been also reported in stellarators. Transport channel decoupling could be driven by any mechanism that leads to a modification of the cross-phase between density and temperature fluctuations caused by changing driving conditions..
The retarding-field energy analyzer (RFA) is a widely used diagnostic tool for ion temperature measurement in the confined-plasma outer boundary. However, temporal resolution in the standard RFA application is restricted to the milliseconds timescale. A new technique has been developed which allows for the measurement of the plasma ion temperature fluctuations <ref>I. Nedzelskiy et al., Rev. Sci. Instrum. 82 (2011) 043505</ref>. The method is based on measurements of two points on the exponentially decaying region of the I–V characteristic with two differently dc-biased RFEA electrodes. Integrating RFA with electrostatic probes would allow measuring temperature and density fluctuations simultaneously and without phase shift effects.

'''Goal'''. We propose to explore the feasibility of measuring the phase relation between density and temperature fluctuations using a combined diagnostic based on Retarting Field Analyzer (RFA) and Langmuir probes that has been recently developed in the TJ-II stellarator.

In addition, the unique capabilities of the dual HIBP system would allow the investigation of density and potential fluctuations in the TJ-II stellarator, from plasma core to plasma edge. Simultaneous, spatially overlapping, measurement of plasma parameters, using HIBP and electrostatic probes, would allow novel probe configurations [e.g. baffled probes] to be tested, and would provide plasma boundary conditions for HIBP calibration.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 1
* Essential diagnostic systems: RFA, Probes
* Type of plasmas (heating configuration): ECRH with density ramp-up and ramp-down to include electron-ion root transitions
* Specific requirements on wall conditioning if any: no
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: Combining retarding-field energy analyzer and electrostatic probes measurements, an approach to measure the phase relation between density and temperature fluctuations using RFA?

2022-01-21T15:26:35Z

Hidalgo: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''Combining retarding-field energy analyzer and electrostatic probes measurements, an approach to measure the phase relation between density and temperature fluctuations using RFA?'''

== Name and affiliation of proponent ==
Igor Nedzelskiy, Carlos Silva (IST)

Mark Koepke (UWV)

Igor Voldiner, Daniel Carralero, Gregorio Martin, J. L. de Pablos, Carlos Hidalgo (CIEMAT)

HIBP Kurchatov and Kharkov team

== Details of contact person at LNF ==
Igor Voldiner

== Description of the activity ==
'''Rational'''. Why is there decoupling between particle and energy transport channels at the transition to improved confinement regimes?. Physics behind uncoupled transport channels is a relevant open question for understanding both ELM control techniques (e.g. using RMP) as part of the ITER base-line scenario and the development of plasma scenarios without ELMs (e.g. I-mode). Interestingly, uncoupled transport channels has been also reported in stellarators. Transport channel decoupling could be driven by any mechanism that leads to a modification of the cross-phase between density and temperature fluctuations caused by changing driving conditions..
The retarding-field energy analyzer (RFA) is a widely used diagnostic tool for ion temperature measurement in the confined-plasma outer boundary. However, temporal resolution in the standard RFA application is restricted to the milliseconds timescale. A new technique has been developed which allows for the measurement of the plasma ion temperature fluctuations <ref>I. Nedzelskiy et al., Rev. Sci. Instrum. 82 (2011) 043505</ref>. The method is based on measurements of two points on the exponentially decaying region of the I–V characteristic with two differently dc-biased RFEA electrodes. Integrating RFA with electrostatic probes would allow measuring temperature and density fluctuations simultaneously and without phase shift effects.

'''Goal'''. We propose to explore the feasibility of measuring the phase relation between density and temperature fluctuations using a combined diagnostic based on Retarting Field Analyzer (RFA) and Langmuir probes that has been recently developed in the TJ-II stellarator.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 1
* Essential diagnostic systems: RFA, Probes
* Type of plasmas (heating configuration): ECRH with density ramp-up and ramp-down to include electron-ion root transitions
* Specific requirements on wall conditioning if any: no
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: SOL Temperature profiles using RFA role of edge radial electric fields

2022-01-21T15:20:47Z

Hidalgo: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: SOL Temperature profiles using RFA: role of edge radial electric fields'''

== Name and affiliation of proponent ==
Igor Nedzelskiy, Carlos Silva (IST)

Mark Koepke (UWV)

Igor Voldiner, Daniel Carralero, Gregorio Martin, J. L. de Pablos, Carlos Hidalgo (CIEMAT)

== Details of contact person at LNF ==
Igor Voldiner

== Description of the activity ==
'''Rational''': The evolution of the ion temperature (Ti) has been previously investigated using RFA measurements during the transition from the electron-root to the ion-root in the Scrape-Off-Layer (SOL) region in TJ-II. As line-averaged density increases above a threshold value, the edge radial electric field reverses from positive to negative values, as predicted by the neoclassical electron-to-ion root transition. Results show a significant decrease in the SOL ion temperature (in the range of 10 – 20 eV) concomitant with the reduction of edge-SOL turbulence spreading controlled by edge radial electric fields <ref>Gustavo Grenfell et al., NF(2020)</ref>.

'''Research goals''': The goal of the experiment would be to study the influence of edge radial electric fields on SOL Ti profiles. With this goal it is proposed to measure the radial profile of Ti in electron and ion root scenarios in ECRH plasmas and NBI regimes.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 4 days
* Essential diagnostic systems: Langmuir probes, RFA, Doppler Reflectometry
* Type of plasmas (heating configuration): ECRH and NBI
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: SOL Temperature profiles using RFA role of edge radial electric fields

2022-01-21T15:20:05Z

Hidalgo: /* Proposal title */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: SOL Temperature profiles using RFA: role of edge radial electric fields'''

== Name and affiliation of proponent ==
Igor Nedzelskiy, Carlos Silva (IST) & Mark Koepke (UWV) & Igor Voldiner, Daniel Carralero, Gregorio Martin, J. L. de Pablos, Carlos Hidalgo (CIEMAT)

== Details of contact person at LNF ==
Igor Voldiner

== Description of the activity ==
'''Rational''': The evolution of the ion temperature (Ti) has been previously investigated using RFA measurements during the transition from the electron-root to the ion-root in the Scrape-Off-Layer (SOL) region in TJ-II. As line-averaged density increases above a threshold value, the edge radial electric field reverses from positive to negative values, as predicted by the neoclassical electron-to-ion root transition. Results show a significant decrease in the SOL ion temperature (in the range of 10 – 20 eV) concomitant with the reduction of edge-SOL turbulence spreading controlled by edge radial electric fields <ref>Gustavo Grenfell et al., NF(2020)</ref>.

'''Research goals''': The goal of the experiment would be to study the influence of edge radial electric fields on SOL Ti profiles. With this goal it is proposed to measure the radial profile of Ti in electron and ion root scenarios in ECRH plasmas and NBI regimes.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 4 days
* Essential diagnostic systems: Langmuir probes, RFA, Doppler Reflectometry
* Type of plasmas (heating configuration): ECRH and NBI
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: 2D mapping of plasma parameters using HIBP

2022-01-21T15:19:05Z

Hidalgo: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: 2D mapping of plasma parameters using HIBP'''

== Name and affiliation of proponent ==
Philipp Khabanov and HIBP team, Kurchatoc Institute, Russia

A. Kozachek and HIBP team, Kharkov Institure, Ukraine

Ciemat team

== Details of contact person at LNF ==
If applicable, enter contact person here or write N/A

== Description of the activity ==

Aim: To expand the area of measurements through the beam energy increas: Mean electric potential φ, mean plasma density ne, RMS of φ, RMS of ne in ECR heated plasmas, NBI heated plasmas and NBI+ECR heated plasmas.

Technique: scanning with probing beam with different energies (90-180 keV) in series of the reproducible TJ-II discharges.

Mandatory requirement: reproducibility of the plasma parameters during experimental day (<5%), density control (<5%), vacuum vessel wall conditioning, lithium coating before experimental day.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
* Essential diagnostic systems:
* Type of plasmas (heating configuration):
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: Influence of edge radial electric fields on impurity transport

2022-01-21T15:17:07Z

Hidalgo: /* Details of contact person at LNF */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II:Influence of edge radial electric fields on impurity transport'''

== Name and affiliation of proponent ==
Dominique Escande, Marseille University

Eduardo de la Cal, Igor Voldiner, Marian Ochando, Carlos Hidalgo, Ciemat

== Details of contact person at LNF ==
Eduardo de la Cal, Ciemat

== Description of the activity ==

Rational. It has been recently argued that the existence of a time delay in the feedback loop relating radiation and impurity production on divertor plates can affect the density limit <ref>D.F. Escande et al 2022 Nucl. Fusion 62 026001</ref>. Furthermore, recent experiments in the TJ-II stellarator have shown the presence and amplification of low frequency Zonal Flows in the vicinity of this limit <ref>D. Fernández-Ruiz et al 2021 Nucl. Fusion 61 126038 </ref>. Whether the threshold radiation value for the density limit would be partially affected by the amplitude of (fluctuating and DC) zonal flows as well as the role of radiation to reduce the free energy available to the turbulence and the ZF-drive are open questions.

Goal. It is proposed to investigate the role of edge radial electric fields and low frequency zonal flows on impurity (He) inward transport in the plasma boundary region in the TJ-II stellarator.

Scenario. Experiments will be carried out in the proximity of the elctron-ion root transition and in the proximity to de NBI density limit.

The ambipolarity condition (i.e. the equality of ion and electron fluxes) determining the radial neoclassical electric field has two stable roots in stellarators: the ion root with typically negative Er, usually achieved in high density plasmas, and the electron root with positive Er, that is typically realized when electrons are subject to strong heating. In addition the neoclassical viscosity vanishes as electron – ion root transition [J.L. Velasco et al., PRL-2012]. This allows large deviations of Er from NC ambipolarity including the amplification of zonal flows [M.A. Pedrosa et al., PRL-2008]. The electron – ion root transition allows to modify DC radial electric fields in a continuos and controlled manner.

Diagnostics. Recently TJ-II diagnostic capabilities have been expanded to include a fast camera system with a gas puffing injection that allows 3 simultaneous filtered frames to apply the He I ratio technique.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 2
* Essential diagnostic systems: Fast caremas with triple boundle
* Type of plasmas (heating configuration): ECRH (electron - ion root) and NBI (density limit)
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: Influence of edge radial electric fields on impurity transport

2022-01-21T15:16:54Z

Hidalgo: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II:Influence of edge radial electric fields on impurity transport'''

== Name and affiliation of proponent ==
Dominique Escande, Marseille University

Eduardo de la Cal, Igor Voldiner, Marian Ochando, Carlos Hidalgo, Ciemat

== Details of contact person at LNF ==
Eduardo de la Cal, Marian Ochando, Carlos Hidalgo

== Description of the activity ==

Rational. It has been recently argued that the existence of a time delay in the feedback loop relating radiation and impurity production on divertor plates can affect the density limit <ref>D.F. Escande et al 2022 Nucl. Fusion 62 026001</ref>. Furthermore, recent experiments in the TJ-II stellarator have shown the presence and amplification of low frequency Zonal Flows in the vicinity of this limit <ref>D. Fernández-Ruiz et al 2021 Nucl. Fusion 61 126038 </ref>. Whether the threshold radiation value for the density limit would be partially affected by the amplitude of (fluctuating and DC) zonal flows as well as the role of radiation to reduce the free energy available to the turbulence and the ZF-drive are open questions.

Goal. It is proposed to investigate the role of edge radial electric fields and low frequency zonal flows on impurity (He) inward transport in the plasma boundary region in the TJ-II stellarator.

Scenario. Experiments will be carried out in the proximity of the elctron-ion root transition and in the proximity to de NBI density limit.

The ambipolarity condition (i.e. the equality of ion and electron fluxes) determining the radial neoclassical electric field has two stable roots in stellarators: the ion root with typically negative Er, usually achieved in high density plasmas, and the electron root with positive Er, that is typically realized when electrons are subject to strong heating. In addition the neoclassical viscosity vanishes as electron – ion root transition [J.L. Velasco et al., PRL-2012]. This allows large deviations of Er from NC ambipolarity including the amplification of zonal flows [M.A. Pedrosa et al., PRL-2008]. The electron – ion root transition allows to modify DC radial electric fields in a continuos and controlled manner.

Diagnostics. Recently TJ-II diagnostic capabilities have been expanded to include a fast camera system with a gas puffing injection that allows 3 simultaneous filtered frames to apply the He I ratio technique.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 2
* Essential diagnostic systems: Fast caremas with triple boundle
* Type of plasmas (heating configuration): ECRH (electron - ion root) and NBI (density limit)
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: On the search of Zonal Flows and the influence of Alfvén Eigenmodes in the TJ-II stellarator

2022-01-21T15:15:23Z

Hidalgo: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: On the search of core Zonal Flows and the influence of Alfvén Eigenmodes in the TJ-II stellarator'''

== Name and affiliation of proponent ==
A. Melnikov and the HIBP Kurchatov Institute team, Russia;

A. Kozachek and the HIBP Kharkov Institute team, Ukrania;

D. Zarzoso, Marseille University, France;

J. Varela, Carlos III University, Spain

Ciemat team

== Details of contact person at LNF ==
Arturo Alonso, Carlos Hidalgo

== Description of the activity ==

While most previous research efforts have been focussed on the excitation and impact of fast ions modes in plasma performance, because of the drain of energy related to fast particle losses with concomitant potential damages in the plasma facing components, there is a growing interest on the impact of fast particles on plasma turbulence and self-organization phenomena. Nonlinear electromagnetic stabilization by suprathermal pressure gradients has been found in gyrokinetic (GK) simulations providing an interpretation of the experimentally observed ion heat flux and stiffness reduction in the JET tokamak <ref> CITRIN, J. et al., Nonlinear Stabilization of Tokamak Microturbulence by Fast Ions, Phys. Rev. Lett 111, 155001(2013)</ref>. Understanding the underlying physics of this non-linear electromagnetic stabilization mechanism is an essential task for future fusion reactors where plasmas will be dominated by fast particle dynamics. The coexistence and interplay of fast ions with main instabilities such as ITG and TEM is an active area of research []. In particular, non-linear excitations of zonal structures by fast particle driven modes have been predicted but validation is still missing <ref> HIDALGO, C. et al., Overview of the TJ-II stellarator research programme towards model validation in fusion plasmas, Nuclear Fusion (2021) </ref>. The plasma scenarios where fast particle driven zonal structures would affect the nonlinear dynamics of AEs or / and turbulent transport is at present an active area of research.

The main focus of this work is the experimental search of zonal flows and the possible influence of fast particle driven modes in the dynamics of zonal flows in the plasma core region of fusion plasmas. In this study both HIBP-I and HIBP-II systems will operate in scanning and fixed point mode to determine plasma profiles as well as plasma potential and density fluctuations in an specific radial location. This unique set-up permits the simultaneous investigation of the radial structure of fluctuations and long-range correlated scales in the whole plasma poloidal cross-section in the TJ-II stellarator.

== International or National funding project or entity ==
Eurofusion (Kharkov team)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 2
* Essential diagnostic systems: Dual HIBP
* Type of plasmas (heating configuration): NBI co & counter
* Specific requirements on wall conditioning if any: Li coating
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: May - June 2022



== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: On the search of Zonal Flows and the influence of Alfvén Eigenmodes in the TJ-II stellarator

2022-01-21T15:11:24Z

Hidalgo: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: On the search of core Zonal Flows and the influence of Alfvén Eigenmodes in the TJ-II stellarator'''

== Name and affiliation of proponent ==
HIBP Kurchatov Institute team, Russia;

HIBP Kharkov Institute team, Ukrania;

Marseille University, France;

Carlos III University, Spain

Ciemat team

== Details of contact person at LNF ==
Arturo Alonso, Carlos Hidalgo

== Description of the activity ==

While most previous research efforts have been focussed on the excitation and impact of fast ions modes in plasma performance, because of the drain of energy related to fast particle losses with concomitant potential damages in the plasma facing components, there is a growing interest on the impact of fast particles on plasma turbulence and self-organization phenomena. Nonlinear electromagnetic stabilization by suprathermal pressure gradients has been found in gyrokinetic (GK) simulations providing an interpretation of the experimentally observed ion heat flux and stiffness reduction in the JET tokamak <ref> CITRIN, J. et al., Nonlinear Stabilization of Tokamak Microturbulence by Fast Ions, Phys. Rev. Lett 111, 155001(2013)</ref>. Understanding the underlying physics of this non-linear electromagnetic stabilization mechanism is an essential task for future fusion reactors where plasmas will be dominated by fast particle dynamics. The coexistence and interplay of fast ions with main instabilities such as ITG and TEM is an active area of research []. In particular, non-linear excitations of zonal structures by fast particle driven modes have been predicted but validation is still missing <ref> HIDALGO, C. et al., Overview of the TJ-II stellarator research programme towards model validation in fusion plasmas, Nuclear Fusion (2021) </ref>. The plasma scenarios where fast particle driven zonal structures would affect the nonlinear dynamics of AEs or / and turbulent transport is at present an active area of research.

The main focus of this work is the experimental search of zonal flows and the possible influence of fast particle driven modes in the dynamics of zonal flows in the plasma core region of fusion plasmas. In this study both HIBP-I and HIBP-II systems will operate in scanning and fixed point mode to determine plasma profiles as well as plasma potential and density fluctuations in an specific radial location. This unique set-up permits the simultaneous investigation of the radial structure of fluctuations and long-range correlated scales in the whole plasma poloidal cross-section in the TJ-II stellarator.

== International or National funding project or entity ==
Eurofusion (Kharkov team)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 2
* Essential diagnostic systems: Dual HIBP
* Type of plasmas (heating configuration): NBI co & counter
* Specific requirements on wall conditioning if any: Li coating
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: May - June 2022



== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: Two dimensional distribution of plasma potential and density

2022-01-21T15:10:11Z

Hidalgo: /* Description of the activity */

== Experimental campaign ==
2021

== Proposal title ==
'''TJ-II: Two dimensional distribution of plasma potential and density'''

== Name and affiliation of proponent ==

Kutchatov HIBP team

Kharkov HIBP team

Ciemat team

== Details of contact person at LNF ==
If applicable, enter contact person here or write N/A

== Description of the activity ==

The first experiments aimed at obtaining the 2D distribution of plasma potential were performed in TJ-II using Heavy Ion Beam Probe (HIBP) with the variation of two parameters: plasma entrance angle and the energy of the Cs+ probing beam in the range 128-148 keV <ref>R. Sharma et al., Physics of Plasmas 27, 062502 (2020)</ref>.

During 2021 HIBP was extended to 176 keV with a beam current up to 300 μA <ref>A. Melnikov et al., PPCF (2021) submitted</ref>

The goal of this proposal is to expand the HIBP energy range [80 - 200 keV] to explore the whole TJ-II poloidal cross-section.

== International or National funding project or entity ==
If applicable, enter funding here or write N/A

== Description of required resources ==

Required resources:

• Number of days of operation: 2

• Essential diagnostic systems: Dual HIBP [May / June]

• Type of plasmas (heating configuration): ECRH & NBI

• Wall conditioning: Sufficient density control for good reproducibility in NBI plasmas.

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2021]]

TJ-II: Two dimensional distribution of plasma potential and density

2022-01-21T15:09:47Z

Hidalgo: /* Description of required resources */

== Experimental campaign ==
2021

== Proposal title ==
'''TJ-II: Two dimensional distribution of plasma potential and density'''

== Name and affiliation of proponent ==

Kutchatov HIBP team

Kharkov HIBP team

Ciemat team

== Details of contact person at LNF ==
If applicable, enter contact person here or write N/A

== Description of the activity ==

The first experiments aimed at obtaining the 2D distribution of plasma potential were performed in TJ-II using Heavy Ion Beam Probe (HIBP) with the variation of two parameters: plasma entrance angle and the energy of the Cs+ probing beam in the range 128-148 keV <ref>R. Sharma et al., Physics of Plasmas 27, 062502 (2020)</ref>.

During 2021 HIBP was extended to 176 keV with a beam current up to 300 μA <ref>RA. Melnikov et al., PPCF (2021) submitted</ref>

The goal of this proposal is to expand the HIBP energy range [80 - 200 keV] to explore the whole TJ-II poloidal cross-section.

== International or National funding project or entity ==
If applicable, enter funding here or write N/A

== Description of required resources ==

Required resources:

• Number of days of operation: 2

• Essential diagnostic systems: Dual HIBP [May / June]

• Type of plasmas (heating configuration): ECRH & NBI

• Wall conditioning: Sufficient density control for good reproducibility in NBI plasmas.

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2021]]

TJ-II: Two dimensional distribution of plasma potential and density

2022-01-21T15:09:32Z

Hidalgo: /* Description of the activity */

== Experimental campaign ==
2021

== Proposal title ==
'''TJ-II: Two dimensional distribution of plasma potential and density'''

== Name and affiliation of proponent ==

Kutchatov HIBP team

Kharkov HIBP team

Ciemat team

== Details of contact person at LNF ==
If applicable, enter contact person here or write N/A

== Description of the activity ==

The first experiments aimed at obtaining the 2D distribution of plasma potential were performed in TJ-II using Heavy Ion Beam Probe (HIBP) with the variation of two parameters: plasma entrance angle and the energy of the Cs+ probing beam in the range 128-148 keV <ref>R. Sharma et al., Physics of Plasmas 27, 062502 (2020)</ref>.

During 2021 HIBP was extended to 176 keV with a beam current up to 300 μA <ref>RA. Melnikov et al., PPCF (2021) submitted</ref>

The goal of this proposal is to expand the HIBP energy range [80 - 200 keV] to explore the whole TJ-II poloidal cross-section.

== International or National funding project or entity ==
If applicable, enter funding here or write N/A

== Description of required resources ==

Required resources:

• Number of days of operation: 3

• Essential diagnostic systems: Dual HIBP [May / June]

• Type of plasmas (heating configuration): ECRH & NBI

• Wall conditioning: Sufficient density control for good reproducibility in NBI plasmas.

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2021]]

TJ-II: Two dimensional distribution of plasma potential and density

2022-01-21T15:09:05Z

Hidalgo: /* Description of the activity */

== Experimental campaign ==
2021

== Proposal title ==
'''TJ-II: Two dimensional distribution of plasma potential and density'''

== Name and affiliation of proponent ==

Kutchatov HIBP team

Kharkov HIBP team

Ciemat team

== Details of contact person at LNF ==
If applicable, enter contact person here or write N/A

== Description of the activity ==

The first experiments aimed at obtaining the 2D distribution of plasma potential were performed in TJ-II using Heavy Ion Beam Probe (HIBP) with the variation of two parameters: plasma entrance angle and the energy of the Cs+ probing beam in the range 128-148 keV <ref>R. Sharma et al., Physics of Plasmas 27, 062502 (2020)</ref>.

During 2021 HIBP was extended to 176 keV with a beam current up to 300 μA <ref>RA. Melnikov et al., 2D distribution of plasma potential and density in the TJ-II stellarator PPCF (2021) submitted</ref>

The goal of this proposal is to expand the HIBP energy range [80 - 200 keV] to explore the whole TJ-II poloidal cross-section.

== International or National funding project or entity ==
If applicable, enter funding here or write N/A

== Description of required resources ==

Required resources:

• Number of days of operation: 3

• Essential diagnostic systems: Dual HIBP [May / June]

• Type of plasmas (heating configuration): ECRH & NBI

• Wall conditioning: Sufficient density control for good reproducibility in NBI plasmas.

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2021]]

TJ-II: 2D mapping of plasma parameters using HIBP

2022-01-20T17:17:09Z

Hidalgo: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: 2D mapping of plasma parameters using HIBP'''

== Name and affiliation of proponent ==
HIBP team, Kurchatoc Institute, Russia
HIBP team, Kharkov Institure, Ukraine
Ciemat team

== Details of contact person at LNF ==
If applicable, enter contact person here or write N/A

== Description of the activity ==

Aim: To expand the area of measurements through the beam energy increas: Mean electric potential φ, mean plasma density ne, RMS of φ, RMS of ne in ECR heated plasmas, NBI heated plasmas and NBI+ECR heated plasmas.

Technique: scanning with probing beam with different energies (90-180 keV) in series of the reproducible TJ-II discharges.

Mandatory requirement: reproducibility of the plasma parameters during experimental day (<5%), density control (<5%), vacuum vessel wall conditioning, lithium coating before experimental day.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
* Essential diagnostic systems:
* Type of plasmas (heating configuration):
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: 2D mapping of plasma parameters using HIBP

2022-01-20T17:16:01Z

Hidalgo: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: 2D mapping of plasma parameters using HIBP'''

== Name and affiliation of proponent ==
HIBP team, Kurchatoc Institute, Russia
HIBP team, Kharkov Institure, Ukrania
Ciemat team

== Details of contact person at LNF ==
If applicable, enter contact person here or write N/A

== Description of the activity ==

Aim: To expand the area of measurements through the beam energy increas: Mean electric potential φ, mean plasma density ne, RMS of φ, RMS of ne in ECR heated plasmas, NBI heated plasmas and NBI+ECR heated plasmas.

Technique: scanning with probing beam with different energies (90-180 keV) in series of the reproducible TJ-II discharges.

Mandatory requirement: reproducibility of the plasma parameters during experimental day (<5%), density control (<5%), vacuum vessel wall conditioning, lithium coating before experimental day.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
* Essential diagnostic systems:
* Type of plasmas (heating configuration):
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: 2D mapping of plasma parameters using HIBP

2022-01-20T17:14:30Z

Hidalgo: /* Description of the activity */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: 2D mapping of plasma parameters using HIBP'''

== Name and affiliation of proponent ==
Enter name, affiliation and ORCID code here

Suggested format:

[https://orcid.org/0000-0000-0000-0000 John Doe], University of Ivory Tower

== Details of contact person at LNF ==
If applicable, enter contact person here or write N/A

== Description of the activity ==

Aim: To expand the area of measurements through the beam energy increas: Mean electric potential φ, mean plasma density ne, RMS of φ, RMS of ne in ECR heated plasmas, NBI heated plasmas and NBI+ECR heated plasmas.

Technique: scanning with probing beam with different energies (90-180 keV) in series of the reproducible TJ-II discharges.

Mandatory requirement: reproducibility of the plasma parameters during experimental day (<5%), density control (<5%), vacuum vessel wall conditioning, lithium coating before experimental day.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
* Essential diagnostic systems:
* Type of plasmas (heating configuration):
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: 2D mapping of plasma parameters using HIBP

2022-01-20T17:12:28Z

Hidalgo: Created page with "== Experimental campaign == Spring 2022 == Proposal title == '''TJ-II: 2D mapping of plasma parameters using HIBP''' == Name and affiliation of proponent == Enter name, affi..."

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: 2D mapping of plasma parameters using HIBP'''

== Name and affiliation of proponent ==
Enter name, affiliation and ORCID code here

Suggested format:

[https://orcid.org/0000-0000-0000-0000 John Doe], University of Ivory Tower

== Details of contact person at LNF ==
If applicable, enter contact person here or write N/A

== Description of the activity ==
Enter description here <ref>A. Einstein, Journal of Exceptional Results (2017)</ref>, including motivation/objectives and experience of the proponent (typically one-two pages)

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
* Essential diagnostic systems:
* Type of plasmas (heating configuration):
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: On the search of Zonal Flows and the influence of Alfvén Eigenmodes in the TJ-II stellarator

2022-01-20T16:55:36Z

Hidalgo: /* Details of contact person at LNF */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: On the search of core Zonal Flows and the influence of Alfvén Eigenmodes in the TJ-II stellarator'''

== Name and affiliation of proponent ==
HIBP Kurchatov Institute team, Russia;
HIBP Kharkov Institute team, Ukrania;
Marseille University, France;
Carlos III University, Spain
Ciemat team

== Details of contact person at LNF ==
Arturo Alonso, Carlos Hidalgo

== Description of the activity ==

While most previous research efforts have been focussed on the excitation and impact of fast ions modes in plasma performance, because of the drain of energy related to fast particle losses with concomitant potential damages in the plasma facing components, there is a growing interest on the impact of fast particles on plasma turbulence and self-organization phenomena. Nonlinear electromagnetic stabilization by suprathermal pressure gradients has been found in gyrokinetic (GK) simulations providing an interpretation of the experimentally observed ion heat flux and stiffness reduction in the JET tokamak <ref> CITRIN, J. et al., Nonlinear Stabilization of Tokamak Microturbulence by Fast Ions, Phys. Rev. Lett 111, 155001(2013)</ref>. Understanding the underlying physics of this non-linear electromagnetic stabilization mechanism is an essential task for future fusion reactors where plasmas will be dominated by fast particle dynamics. The coexistence and interplay of fast ions with main instabilities such as ITG and TEM is an active area of research []. In particular, non-linear excitations of zonal structures by fast particle driven modes have been predicted but validation is still missing <ref> HIDALGO, C. et al., Overview of the TJ-II stellarator research programme towards model validation in fusion plasmas, Nuclear Fusion (2021) </ref>. The plasma scenarios where fast particle driven zonal structures would affect the nonlinear dynamics of AEs or / and turbulent transport is at present an active area of research.

The main focus of this work is the experimental search of zonal flows and the possible influence of fast particle driven modes in the dynamics of zonal flows in the plasma core region of fusion plasmas. In this study both HIBP-I and HIBP-II systems will operate in scanning and fixed point mode to determine plasma profiles as well as plasma potential and density fluctuations in an specific radial location. This unique set-up permits the simultaneous investigation of the radial structure of fluctuations and long-range correlated scales in the whole plasma poloidal cross-section in the TJ-II stellarator.

== International or National funding project or entity ==
Eurofusion (Kharkov team)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 2
* Essential diagnostic systems: Dual HIBP
* Type of plasmas (heating configuration): NBI co & counter
* Specific requirements on wall conditioning if any: Li coating
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: May - June 2022



== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: On the search of Zonal Flows and the influence of Alfvén Eigenmodes in the TJ-II stellarator

2022-01-20T16:55:10Z

Hidalgo: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: On the search of core Zonal Flows and the influence of Alfvén Eigenmodes in the TJ-II stellarator'''

== Name and affiliation of proponent ==
HIBP Kurchatov Institute team, Russia;
HIBP Kharkov Institute team, Ukrania;
Marseille University, France;
Carlos III University, Spain
Ciemat team

== Details of contact person at LNF ==
Arturo Alonso, Jose Luis de Pablos, Carlos Hidalgo

== Description of the activity ==

While most previous research efforts have been focussed on the excitation and impact of fast ions modes in plasma performance, because of the drain of energy related to fast particle losses with concomitant potential damages in the plasma facing components, there is a growing interest on the impact of fast particles on plasma turbulence and self-organization phenomena. Nonlinear electromagnetic stabilization by suprathermal pressure gradients has been found in gyrokinetic (GK) simulations providing an interpretation of the experimentally observed ion heat flux and stiffness reduction in the JET tokamak <ref> CITRIN, J. et al., Nonlinear Stabilization of Tokamak Microturbulence by Fast Ions, Phys. Rev. Lett 111, 155001(2013)</ref>. Understanding the underlying physics of this non-linear electromagnetic stabilization mechanism is an essential task for future fusion reactors where plasmas will be dominated by fast particle dynamics. The coexistence and interplay of fast ions with main instabilities such as ITG and TEM is an active area of research []. In particular, non-linear excitations of zonal structures by fast particle driven modes have been predicted but validation is still missing <ref> HIDALGO, C. et al., Overview of the TJ-II stellarator research programme towards model validation in fusion plasmas, Nuclear Fusion (2021) </ref>. The plasma scenarios where fast particle driven zonal structures would affect the nonlinear dynamics of AEs or / and turbulent transport is at present an active area of research.

The main focus of this work is the experimental search of zonal flows and the possible influence of fast particle driven modes in the dynamics of zonal flows in the plasma core region of fusion plasmas. In this study both HIBP-I and HIBP-II systems will operate in scanning and fixed point mode to determine plasma profiles as well as plasma potential and density fluctuations in an specific radial location. This unique set-up permits the simultaneous investigation of the radial structure of fluctuations and long-range correlated scales in the whole plasma poloidal cross-section in the TJ-II stellarator.

== International or National funding project or entity ==
Eurofusion (Kharkov team)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 2
* Essential diagnostic systems: Dual HIBP
* Type of plasmas (heating configuration): NBI co & counter
* Specific requirements on wall conditioning if any: Li coating
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: May - June 2022



== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: Influence of edge radial electric fields on impurity transport

2022-01-20T16:53:50Z

Hidalgo: /* Description of required resources */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II:Influence of edge radial electric fields on impurity transport'''

== Name and affiliation of proponent ==
Dominique Escande, Marseille University
and TJ-II team

== Details of contact person at LNF ==
Eduardo de la Cal, Marian Ochando, Carlos Hidalgo

== Description of the activity ==

Rational. It has been recently argued that the existence of a time delay in the feedback loop relating radiation and impurity production on divertor plates can affect the density limit <ref>D.F. Escande et al 2022 Nucl. Fusion 62 026001</ref>. Furthermore, recent experiments in the TJ-II stellarator have shown the presence and amplification of low frequency Zonal Flows in the vicinity of this limit <ref>D. Fernández-Ruiz et al 2021 Nucl. Fusion 61 126038 </ref>. Whether the threshold radiation value for the density limit would be partially affected by the amplitude of (fluctuating and DC) zonal flows as well as the role of radiation to reduce the free energy available to the turbulence and the ZF-drive are open questions.

Goal. It is proposed to investigate the role of edge radial electric fields and low frequency zonal flows on impurity (He) inward transport in the plasma boundary region in the TJ-II stellarator.

Scenario. Experiments will be carried out in the proximity of the elctron-ion root transition and in the proximity to de NBI density limit.

The ambipolarity condition (i.e. the equality of ion and electron fluxes) determining the radial neoclassical electric field has two stable roots in stellarators: the ion root with typically negative Er, usually achieved in high density plasmas, and the electron root with positive Er, that is typically realized when electrons are subject to strong heating. In addition the neoclassical viscosity vanishes as electron – ion root transition [J.L. Velasco et al., PRL-2012]. This allows large deviations of Er from NC ambipolarity including the amplification of zonal flows [M.A. Pedrosa et al., PRL-2008]. The electron – ion root transition allows to modify DC radial electric fields in a continuos and controlled manner.

Diagnostics. Recently TJ-II diagnostic capabilities have been expanded to include a fast camera system with a gas puffing injection that allows 3 simultaneous filtered frames to apply the He I ratio technique.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 2
* Essential diagnostic systems: Fast caremas with triple boundle
* Type of plasmas (heating configuration): ECRH (electron - ion root) and NBI (density limit)
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: Influence of edge radial electric fields on impurity transport

2022-01-20T16:53:15Z

Hidalgo: /* Description of the activity */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II:Influence of edge radial electric fields on impurity transport'''

== Name and affiliation of proponent ==
Dominique Escande, Marseille University
and TJ-II team

== Details of contact person at LNF ==
Eduardo de la Cal, Marian Ochando, Carlos Hidalgo

== Description of the activity ==

Rational. It has been recently argued that the existence of a time delay in the feedback loop relating radiation and impurity production on divertor plates can affect the density limit <ref>D.F. Escande et al 2022 Nucl. Fusion 62 026001</ref>. Furthermore, recent experiments in the TJ-II stellarator have shown the presence and amplification of low frequency Zonal Flows in the vicinity of this limit <ref>D. Fernández-Ruiz et al 2021 Nucl. Fusion 61 126038 </ref>. Whether the threshold radiation value for the density limit would be partially affected by the amplitude of (fluctuating and DC) zonal flows as well as the role of radiation to reduce the free energy available to the turbulence and the ZF-drive are open questions.

Goal. It is proposed to investigate the role of edge radial electric fields and low frequency zonal flows on impurity (He) inward transport in the plasma boundary region in the TJ-II stellarator.

Scenario. Experiments will be carried out in the proximity of the elctron-ion root transition and in the proximity to de NBI density limit.

The ambipolarity condition (i.e. the equality of ion and electron fluxes) determining the radial neoclassical electric field has two stable roots in stellarators: the ion root with typically negative Er, usually achieved in high density plasmas, and the electron root with positive Er, that is typically realized when electrons are subject to strong heating. In addition the neoclassical viscosity vanishes as electron – ion root transition [J.L. Velasco et al., PRL-2012]. This allows large deviations of Er from NC ambipolarity including the amplification of zonal flows [M.A. Pedrosa et al., PRL-2008]. The electron – ion root transition allows to modify DC radial electric fields in a continuos and controlled manner.

Diagnostics. Recently TJ-II diagnostic capabilities have been expanded to include a fast camera system with a gas puffing injection that allows 3 simultaneous filtered frames to apply the He I ratio technique.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 1
* Essential diagnostic systems: Fast caremas with triple boundle
* Type of plasmas (heating configuration): ECRH
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: Influence of edge radial electric fields on impurity transport

2022-01-20T16:52:12Z

Hidalgo: /* Details of contact person at LNF */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II:Influence of edge radial electric fields on impurity transport'''

== Name and affiliation of proponent ==
Dominique Escande, Marseille University
and TJ-II team

== Details of contact person at LNF ==
Eduardo de la Cal, Marian Ochando, Carlos Hidalgo

== Description of the activity ==

Rational. It has been recently argued that the existence of a time delay in the feedback loop relating radiation and impurity production on divertor plates can affect the density limit <ref>D.F. Escande et al 2022 Nucl. Fusion 62 026001</ref>. Furthermore, recent experiments in the TJ-II stellarator have shown the presence and amplification of low frequency Zonal Flows in the vicinity of this limit <ref>D. Fernández-Ruiz et al 2021 Nucl. Fusion 61 126038 </ref>. Whether the threshold radiation value for the density limit would be partially affected by the amplitude of (fluctuating and DC) zonal flows as well as the role of radiation to reduce the free energy available to the turbulence and the ZF-drive are open questions.

Goal. It is proposed to investigate the role of edge radial electric fields and low frequency zonal flows on impurity (He) inward transport in the plasma boundary region in the TJ-II stellarator.

Scenario. Experiments will be carried out in the proximity of the elctron-ion root transition.
The ambipolarity condition (i.e. the equality of ion and electron fluxes) determining the radial neoclassical electric field has two stable roots in stellarators: the ion root with typically negative Er, usually achieved in high density plasmas, and the electron root with positive Er, that is typically realized when electrons are subject to strong heating. In addition the neoclassical viscosity vanishes as electron – ion root transition [J.L. Velasco et al., PRL-2012]. This allows large deviations of Er from NC ambipolarity including the amplification of zonal flows [M.A. Pedrosa et al., PRL-2008]. The electron – ion root transition allows to modify DC radial electric fields in a continuos and controlled manner.

Diagnostics. Recently TJ-II diagnostic capabilities have been expanded to include a fast camera system with a gas puffing injection that allows 3 simultaneous filtered frames to apply the He I ratio technique.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 1
* Essential diagnostic systems: Fast caremas with triple boundle
* Type of plasmas (heating configuration): ECRH
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: Influence of edge radial electric fields on impurity transport

2022-01-20T16:35:46Z

Hidalgo: /* Description of the activity */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II:Influence of edge radial electric fields on impurity transport'''

== Name and affiliation of proponent ==
Dominique Escande, Marseille University
and TJ-II team

== Details of contact person at LNF ==
Carlos Hidalgo

== Description of the activity ==

Rational. It has been recently argued that the existence of a time delay in the feedback loop relating radiation and impurity production on divertor plates can affect the density limit <ref>D.F. Escande et al 2022 Nucl. Fusion 62 026001</ref>. Furthermore, recent experiments in the TJ-II stellarator have shown the presence and amplification of low frequency Zonal Flows in the vicinity of this limit <ref>D. Fernández-Ruiz et al 2021 Nucl. Fusion 61 126038 </ref>. Whether the threshold radiation value for the density limit would be partially affected by the amplitude of (fluctuating and DC) zonal flows as well as the role of radiation to reduce the free energy available to the turbulence and the ZF-drive are open questions.

Goal. It is proposed to investigate the role of edge radial electric fields and low frequency zonal flows on impurity (He) inward transport in the plasma boundary region in the TJ-II stellarator.

Scenario. Experiments will be carried out in the proximity of the elctron-ion root transition.
The ambipolarity condition (i.e. the equality of ion and electron fluxes) determining the radial neoclassical electric field has two stable roots in stellarators: the ion root with typically negative Er, usually achieved in high density plasmas, and the electron root with positive Er, that is typically realized when electrons are subject to strong heating. In addition the neoclassical viscosity vanishes as electron – ion root transition [J.L. Velasco et al., PRL-2012]. This allows large deviations of Er from NC ambipolarity including the amplification of zonal flows [M.A. Pedrosa et al., PRL-2008]. The electron – ion root transition allows to modify DC radial electric fields in a continuos and controlled manner.

Diagnostics. Recently TJ-II diagnostic capabilities have been expanded to include a fast camera system with a gas puffing injection that allows 3 simultaneous filtered frames to apply the He I ratio technique.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 1
* Essential diagnostic systems: Fast caremas with triple boundle
* Type of plasmas (heating configuration): ECRH
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: Influence of edge radial electric fields on impurity transport

2022-01-20T16:35:21Z

Hidalgo: /* Description of required resources */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II:Influence of edge radial electric fields on impurity transport'''

== Name and affiliation of proponent ==
Dominique Escande, Marseille University
and TJ-II team

== Details of contact person at LNF ==
Carlos Hidalgo

== Description of the activity ==
Enter description here <ref>A. Einstein, Journal of Exceptional Results (2017)</ref>, including motivation/objectives and experience of the proponent (typically one-two pages)

Rational. It has been recently argued that the existence of a time delay in the feedback loop relating radiation and impurity production on divertor plates can affect the density limit <ref>D.F. Escande et al 2022 Nucl. Fusion 62 026001</ref>. Furthermore, recent experiments in the TJ-II stellarator have shown the presence and amplification of low frequency Zonal Flows in the vicinity of this limit <ref>D. Fernández-Ruiz et al 2021 Nucl. Fusion 61 126038 </ref>. Whether the threshold radiation value for the density limit would be partially affected by the amplitude of (fluctuating and DC) zonal flows as well as the role of radiation to reduce the free energy available to the turbulence and the ZF-drive are open questions.

Goal. It is proposed to investigate the role of edge radial electric fields and low frequency zonal flows on impurity (He) inward transport in the plasma boundary region in the TJ-II stellarator.

Scenario. Experiments will be carried out in the proximity of the elctron-ion root transition.
The ambipolarity condition (i.e. the equality of ion and electron fluxes) determining the radial neoclassical electric field has two stable roots in stellarators: the ion root with typically negative Er, usually achieved in high density plasmas, and the electron root with positive Er, that is typically realized when electrons are subject to strong heating. In addition the neoclassical viscosity vanishes as electron – ion root transition [J.L. Velasco et al., PRL-2012]. This allows large deviations of Er from NC ambipolarity including the amplification of zonal flows [M.A. Pedrosa et al., PRL-2008]. The electron – ion root transition allows to modify DC radial electric fields in a continuos and controlled manner.

Diagnostics. Recently TJ-II diagnostic capabilities have been expanded to include a fast camera system with a gas puffing injection that allows 3 simultaneous filtered frames to apply the He I ratio technique.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 1
* Essential diagnostic systems: Fast caremas with triple boundle
* Type of plasmas (heating configuration): ECRH
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: Influence of edge radial electric fields on impurity transport

2022-01-20T16:34:14Z

Hidalgo: /* Description of the activity */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II:Influence of edge radial electric fields on impurity transport'''

== Name and affiliation of proponent ==
Dominique Escande, Marseille University
and TJ-II team

== Details of contact person at LNF ==
Carlos Hidalgo

== Description of the activity ==
Enter description here <ref>A. Einstein, Journal of Exceptional Results (2017)</ref>, including motivation/objectives and experience of the proponent (typically one-two pages)

Rational. It has been recently argued that the existence of a time delay in the feedback loop relating radiation and impurity production on divertor plates can affect the density limit <ref>D.F. Escande et al 2022 Nucl. Fusion 62 026001</ref>. Furthermore, recent experiments in the TJ-II stellarator have shown the presence and amplification of low frequency Zonal Flows in the vicinity of this limit <ref>D. Fernández-Ruiz et al 2021 Nucl. Fusion 61 126038 </ref>. Whether the threshold radiation value for the density limit would be partially affected by the amplitude of (fluctuating and DC) zonal flows as well as the role of radiation to reduce the free energy available to the turbulence and the ZF-drive are open questions.

Goal. It is proposed to investigate the role of edge radial electric fields and low frequency zonal flows on impurity (He) inward transport in the plasma boundary region in the TJ-II stellarator.

Scenario. Experiments will be carried out in the proximity of the elctron-ion root transition.
The ambipolarity condition (i.e. the equality of ion and electron fluxes) determining the radial neoclassical electric field has two stable roots in stellarators: the ion root with typically negative Er, usually achieved in high density plasmas, and the electron root with positive Er, that is typically realized when electrons are subject to strong heating. In addition the neoclassical viscosity vanishes as electron – ion root transition [J.L. Velasco et al., PRL-2012]. This allows large deviations of Er from NC ambipolarity including the amplification of zonal flows [M.A. Pedrosa et al., PRL-2008]. The electron – ion root transition allows to modify DC radial electric fields in a continuos and controlled manner.

Diagnostics. Recently TJ-II diagnostic capabilities have been expanded to include a fast camera system with a gas puffing injection that allows 3 simultaneous filtered frames to apply the He I ratio technique.

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
* Essential diagnostic systems:
* Type of plasmas (heating configuration):
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: Influence of edge radial electric fields on impurity transport

2022-01-20T16:32:30Z

Hidalgo: /* Details of contact person at LNF */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II:Influence of edge radial electric fields on impurity transport'''

== Name and affiliation of proponent ==
Dominique Escande, Marseille University
and TJ-II team

== Details of contact person at LNF ==
Carlos Hidalgo

== Description of the activity ==
Enter description here <ref>A. Einstein, Journal of Exceptional Results (2017)</ref>, including motivation/objectives and experience of the proponent (typically one-two pages)

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
* Essential diagnostic systems:
* Type of plasmas (heating configuration):
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: Influence of edge radial electric fields on impurity transport

2022-01-20T16:32:03Z

Hidalgo: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II:Influence of edge radial electric fields on impurity transport'''

== Name and affiliation of proponent ==
Dominique Escande, Marseille University
and TJ-II team

== Details of contact person at LNF ==
If applicable, enter contact person here or write N/A

== Description of the activity ==
Enter description here <ref>A. Einstein, Journal of Exceptional Results (2017)</ref>, including motivation/objectives and experience of the proponent (typically one-two pages)

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
* Essential diagnostic systems:
* Type of plasmas (heating configuration):
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: Influence of edge radial electric fields on impurity transport

2022-01-20T16:31:52Z

Hidalgo: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II:Influence of edge radial electric fields on impurity transport'''

== Name and affiliation of proponent ==
Dominique Escande, Marseille University
TJ-II team

== Details of contact person at LNF ==
If applicable, enter contact person here or write N/A

== Description of the activity ==
Enter description here <ref>A. Einstein, Journal of Exceptional Results (2017)</ref>, including motivation/objectives and experience of the proponent (typically one-two pages)

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
* Essential diagnostic systems:
* Type of plasmas (heating configuration):
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: Influence of edge radial electric fields on impurity transport

2022-01-20T16:31:32Z

Hidalgo: /* Name and affiliation of proponent */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II:Influence of edge radial electric fields on impurity transport'''

== Name and affiliation of proponent ==
Dominique Escande, Marseille University

Suggested format:

[https://orcid.org/0000-0000-0000-0000 John Doe], University of Ivory Tower

== Details of contact person at LNF ==
If applicable, enter contact person here or write N/A

== Description of the activity ==
Enter description here <ref>A. Einstein, Journal of Exceptional Results (2017)</ref>, including motivation/objectives and experience of the proponent (typically one-two pages)

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
* Essential diagnostic systems:
* Type of plasmas (heating configuration):
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: Influence of edge radial electric fields on impurity transport

2022-01-20T16:30:22Z

Hidalgo: Created page with "== Experimental campaign == Spring 2022 == Proposal title == '''TJ-II:Influence of edge radial electric fields on impurity transport''' == Name and affiliation of proponent ..."

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II:Influence of edge radial electric fields on impurity transport'''

== Name and affiliation of proponent ==
Enter name, affiliation and ORCID code here

Suggested format:

[https://orcid.org/0000-0000-0000-0000 John Doe], University of Ivory Tower

== Details of contact person at LNF ==
If applicable, enter contact person here or write N/A

== Description of the activity ==
Enter description here <ref>A. Einstein, Journal of Exceptional Results (2017)</ref>, including motivation/objectives and experience of the proponent (typically one-two pages)

== International or National funding project or entity ==
Include funding here (grants, national plans)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation:
* Essential diagnostic systems:
* Type of plasmas (heating configuration):
* Specific requirements on wall conditioning if any:
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: On the search of Zonal Flows and the influence of Alfvén Eigenmodes in the TJ-II stellarator

2022-01-18T10:22:33Z

Hidalgo: /* Details of contact person at LNF */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: On the search of core Zonal Flows and the influence of Alfvén Eigenmodes in the TJ-II stellarator'''

== Name and affiliation of proponent ==
HIBP Kurchatov Institute team, Russia;
HIBP Kharkov Institute team, Ukrania;
Ciemat team

== Details of contact person at LNF ==
Arturo Alonso, Jose Luis de Pablos, Carlos Hidalgo

== Description of the activity ==

While most previous research efforts have been focussed on the excitation and impact of fast ions modes in plasma performance, because of the drain of energy related to fast particle losses with concomitant potential damages in the plasma facing components, there is a growing interest on the impact of fast particles on plasma turbulence and self-organization phenomena. Nonlinear electromagnetic stabilization by suprathermal pressure gradients has been found in gyrokinetic (GK) simulations providing an interpretation of the experimentally observed ion heat flux and stiffness reduction in the JET tokamak <ref> CITRIN, J. et al., Nonlinear Stabilization of Tokamak Microturbulence by Fast Ions, Phys. Rev. Lett 111, 155001(2013)</ref>. Understanding the underlying physics of this non-linear electromagnetic stabilization mechanism is an essential task for future fusion reactors where plasmas will be dominated by fast particle dynamics. The coexistence and interplay of fast ions with main instabilities such as ITG and TEM is an active area of research []. In particular, non-linear excitations of zonal structures by fast particle driven modes have been predicted but validation is still missing <ref> HIDALGO, C. et al., Overview of the TJ-II stellarator research programme towards model validation in fusion plasmas, Nuclear Fusion (2021) </ref>. The plasma scenarios where fast particle driven zonal structures would affect the nonlinear dynamics of AEs or / and turbulent transport is at present an active area of research.

The main focus of this work is the experimental search of zonal flows and the possible influence of fast particle driven modes in the dynamics of zonal flows in the plasma core region of fusion plasmas. In this study both HIBP-I and HIBP-II systems will operate in scanning and fixed point mode to determine plasma profiles as well as plasma potential and density fluctuations in an specific radial location. This unique set-up permits the simultaneous investigation of the radial structure of fluctuations and long-range correlated scales in the whole plasma poloidal cross-section in the TJ-II stellarator.

== International or National funding project or entity ==
Eurofusion (Kharkov team)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 2
* Essential diagnostic systems: Dual HIBP
* Type of plasmas (heating configuration): NBI co & counter
* Specific requirements on wall conditioning if any: Li coating
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: May - June 2022



== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: On the search of Zonal Flows and the influence of Alfvén Eigenmodes in the TJ-II stellarator

2022-01-18T10:21:46Z

Hidalgo: /* Preferred dates and degree of flexibility */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: On the search of core Zonal Flows and the influence of Alfvén Eigenmodes in the TJ-II stellarator'''

== Name and affiliation of proponent ==
HIBP Kurchatov Institute team, Russia;
HIBP Kharkov Institute team, Ukrania;
Ciemat team

== Details of contact person at LNF ==
Arturo Alonso, Carlos Hidalgo

== Description of the activity ==

While most previous research efforts have been focussed on the excitation and impact of fast ions modes in plasma performance, because of the drain of energy related to fast particle losses with concomitant potential damages in the plasma facing components, there is a growing interest on the impact of fast particles on plasma turbulence and self-organization phenomena. Nonlinear electromagnetic stabilization by suprathermal pressure gradients has been found in gyrokinetic (GK) simulations providing an interpretation of the experimentally observed ion heat flux and stiffness reduction in the JET tokamak <ref> CITRIN, J. et al., Nonlinear Stabilization of Tokamak Microturbulence by Fast Ions, Phys. Rev. Lett 111, 155001(2013)</ref>. Understanding the underlying physics of this non-linear electromagnetic stabilization mechanism is an essential task for future fusion reactors where plasmas will be dominated by fast particle dynamics. The coexistence and interplay of fast ions with main instabilities such as ITG and TEM is an active area of research []. In particular, non-linear excitations of zonal structures by fast particle driven modes have been predicted but validation is still missing <ref> HIDALGO, C. et al., Overview of the TJ-II stellarator research programme towards model validation in fusion plasmas, Nuclear Fusion (2021) </ref>. The plasma scenarios where fast particle driven zonal structures would affect the nonlinear dynamics of AEs or / and turbulent transport is at present an active area of research.

The main focus of this work is the experimental search of zonal flows and the possible influence of fast particle driven modes in the dynamics of zonal flows in the plasma core region of fusion plasmas. In this study both HIBP-I and HIBP-II systems will operate in scanning and fixed point mode to determine plasma profiles as well as plasma potential and density fluctuations in an specific radial location. This unique set-up permits the simultaneous investigation of the radial structure of fluctuations and long-range correlated scales in the whole plasma poloidal cross-section in the TJ-II stellarator.

== International or National funding project or entity ==
Eurofusion (Kharkov team)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 2
* Essential diagnostic systems: Dual HIBP
* Type of plasmas (heating configuration): NBI co & counter
* Specific requirements on wall conditioning if any: Li coating
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: May - June 2022



== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: On the search of Zonal Flows and the influence of Alfvén Eigenmodes in the TJ-II stellarator

2022-01-18T10:21:21Z

Hidalgo: /* Details of contact person at LNF */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: On the search of core Zonal Flows and the influence of Alfvén Eigenmodes in the TJ-II stellarator'''

== Name and affiliation of proponent ==
HIBP Kurchatov Institute team, Russia;
HIBP Kharkov Institute team, Ukrania;
Ciemat team

== Details of contact person at LNF ==
Arturo Alonso, Carlos Hidalgo

== Description of the activity ==

While most previous research efforts have been focussed on the excitation and impact of fast ions modes in plasma performance, because of the drain of energy related to fast particle losses with concomitant potential damages in the plasma facing components, there is a growing interest on the impact of fast particles on plasma turbulence and self-organization phenomena. Nonlinear electromagnetic stabilization by suprathermal pressure gradients has been found in gyrokinetic (GK) simulations providing an interpretation of the experimentally observed ion heat flux and stiffness reduction in the JET tokamak <ref> CITRIN, J. et al., Nonlinear Stabilization of Tokamak Microturbulence by Fast Ions, Phys. Rev. Lett 111, 155001(2013)</ref>. Understanding the underlying physics of this non-linear electromagnetic stabilization mechanism is an essential task for future fusion reactors where plasmas will be dominated by fast particle dynamics. The coexistence and interplay of fast ions with main instabilities such as ITG and TEM is an active area of research []. In particular, non-linear excitations of zonal structures by fast particle driven modes have been predicted but validation is still missing <ref> HIDALGO, C. et al., Overview of the TJ-II stellarator research programme towards model validation in fusion plasmas, Nuclear Fusion (2021) </ref>. The plasma scenarios where fast particle driven zonal structures would affect the nonlinear dynamics of AEs or / and turbulent transport is at present an active area of research.

The main focus of this work is the experimental search of zonal flows and the possible influence of fast particle driven modes in the dynamics of zonal flows in the plasma core region of fusion plasmas. In this study both HIBP-I and HIBP-II systems will operate in scanning and fixed point mode to determine plasma profiles as well as plasma potential and density fluctuations in an specific radial location. This unique set-up permits the simultaneous investigation of the radial structure of fluctuations and long-range correlated scales in the whole plasma poloidal cross-section in the TJ-II stellarator.

== International or National funding project or entity ==
Eurofusion (Kharkov team)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 2
* Essential diagnostic systems: Dual HIBP
* Type of plasmas (heating configuration): NBI co & counter
* Specific requirements on wall conditioning if any: Li coating
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]

TJ-II: On the search of Zonal Flows and the influence of Alfvén Eigenmodes in the TJ-II stellarator

2022-01-18T10:20:53Z

Hidalgo: /* International or National funding project or entity */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: On the search of core Zonal Flows and the influence of Alfvén Eigenmodes in the TJ-II stellarator'''

== Name and affiliation of proponent ==
HIBP Kurchatov Institute team, Russia;
HIBP Kharkov Institute team, Ukrania;
Ciemat team

== Details of contact person at LNF ==
Arturo Alonso

== Description of the activity ==

While most previous research efforts have been focussed on the excitation and impact of fast ions modes in plasma performance, because of the drain of energy related to fast particle losses with concomitant potential damages in the plasma facing components, there is a growing interest on the impact of fast particles on plasma turbulence and self-organization phenomena. Nonlinear electromagnetic stabilization by suprathermal pressure gradients has been found in gyrokinetic (GK) simulations providing an interpretation of the experimentally observed ion heat flux and stiffness reduction in the JET tokamak <ref> CITRIN, J. et al., Nonlinear Stabilization of Tokamak Microturbulence by Fast Ions, Phys. Rev. Lett 111, 155001(2013)</ref>. Understanding the underlying physics of this non-linear electromagnetic stabilization mechanism is an essential task for future fusion reactors where plasmas will be dominated by fast particle dynamics. The coexistence and interplay of fast ions with main instabilities such as ITG and TEM is an active area of research []. In particular, non-linear excitations of zonal structures by fast particle driven modes have been predicted but validation is still missing <ref> HIDALGO, C. et al., Overview of the TJ-II stellarator research programme towards model validation in fusion plasmas, Nuclear Fusion (2021) </ref>. The plasma scenarios where fast particle driven zonal structures would affect the nonlinear dynamics of AEs or / and turbulent transport is at present an active area of research.

The main focus of this work is the experimental search of zonal flows and the possible influence of fast particle driven modes in the dynamics of zonal flows in the plasma core region of fusion plasmas. In this study both HIBP-I and HIBP-II systems will operate in scanning and fixed point mode to determine plasma profiles as well as plasma potential and density fluctuations in an specific radial location. This unique set-up permits the simultaneous investigation of the radial structure of fluctuations and long-range correlated scales in the whole plasma poloidal cross-section in the TJ-II stellarator.

== International or National funding project or entity ==
Eurofusion (Kharkov team)

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 2
* Essential diagnostic systems: Dual HIBP
* Type of plasmas (heating configuration): NBI co & counter
* Specific requirements on wall conditioning if any: Li coating
* External users: need a local computer account for data access: yes/no
* Any external equipment to be integrated? Provide description and integration needs:

== Preferred dates and degree of flexibility ==
Preferred dates: (format dd-mm-yyyy)


== References ==
<references />

<hr>
[[TJ-II:Experimental proposals|Back to list of experimental proposals]]

[[Category:TJ-II internal documents]]
[[Category:TJ-II experimental proposals Spring 2022]]