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TJ-II: Measurements using Gas Puff Imaging system

2022-01-21T14:02:07Z

Igor voldiner: /* Description of required resources */

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: Measurements using Gas Puff Imaging system'''

== Name and affiliation of proponent ==
I. Voldiner,E. de la Cal, B. van Milligen, D. Tafalla and C. Hidalgo LNF, Ciemat

== Details of contact person at LNF ==
I. Voldiner

== Description of the activity ==
'''Rational''': Ongoing development and refinement of a novel gas injection system is underway at TJ-II stellarator. The objective is to get 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 so as to study plasma turbulence. Incremental improvements in hardware and analysis prompt new tests in experimental environment.

'''Goals''': Obtain simultaneous measurements of edge plasma density and temperature profiles using GPI and other diagnostics such as Reflectometry, Langmuir probes, Supersonic He-I spectroscopy and Thomson Scattering [1] to validate and determine the applicability range of the Collisional Radiative Model. Simultaneously limits of applicability and effects of the gas puffing on discharge parameters will be explored in higher variety of scenarios to further explore plasma turbulence [2].

[1] E. de la Cal E., Guasp J. and TJ-II Team 2011 Plasma Phys. Control. Fusion 53 085006

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

== 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: 3 (1 day in March - ECRH, 2 days in April-June - NBI)
* Essential diagnostic systems: GPI, Supersonic He-puffing, AM Reflectometry, TS, Langmuir probes
* Type of plasmas (heating configuration): ECRH and NBI
* Specific requirements on wall conditioning if any: good plasma wall condition is requiered in NBI due to additional gas puffing
* 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: Measurements using Gas Puff Imaging system

2022-01-21T14:01:37Z

Igor voldiner: Created page with "== Experimental campaign == Spring 2022 == Proposal title == '''TJ-II: Measurements using Gas Puff Imaging system''' == Name and affiliation of proponent == I. Voldiner,E. d..."

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''TJ-II: Measurements using Gas Puff Imaging system'''

== Name and affiliation of proponent ==
I. Voldiner,E. de la Cal, B. van Milligen, D. Tafalla and C. Hidalgo LNF, Ciemat

== Details of contact person at LNF ==
I. Voldiner

== Description of the activity ==
'''Rational''': Ongoing development and refinement of a novel gas injection system is underway at TJ-II stellarator. The objective is to get 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 so as to study plasma turbulence. Incremental improvements in hardware and analysis prompt new tests in experimental environment.

'''Goals''': Obtain simultaneous measurements of edge plasma density and temperature profiles using GPI and other diagnostics such as Reflectometry, Langmuir probes, Supersonic He-I spectroscopy and Thomson Scattering [1] to validate and determine the applicability range of the Collisional Radiative Model. Simultaneously limits of applicability and effects of the gas puffing on discharge parameters will be explored in higher variety of scenarios to further explore plasma turbulence [2].

[1] E. de la Cal E., Guasp J. and TJ-II Team 2011 Plasma Phys. Control. Fusion 53 085006

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

== 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: 3 (1 day in March - ECRH, 2 days in April-June - NBI)
* Essential diagnostic systems: GPI, Supersonic He-puffing, AM Reflectometry, TS
* Type of plasmas (heating configuration): ECRH and NBI
* Specific requirements on wall conditioning if any: good plasma wall condition is requiered in NBI due to additional gas puffing
* 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?

2022-01-19T16:02:33Z

Igor voldiner: Phase measurements between n_e, T_e and T_i fluctuations via Langmuir probes and RFA

== 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)

== 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]]

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

2022-01-18T12:52:23Z

Igor voldiner: Igor voldiner moved page SOL Temperature profiles using RFA in TJ-II: role of edge radial electric fields to TJ-II: SOL Temperature profiles using RFA role of edge radial electric fields: to comply with the naming convention

#REDIRECT [[TJ-II: SOL Temperature profiles using RFA role of edge radial electric fields]]

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

2022-01-18T12:52:22Z

== 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

2022-01-18T12:15:24Z

Igor voldiner:

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

2022-01-18T12:01:55Z

Igor voldiner: Created page with "== Experimental campaign == Spring 2022 == Proposal title == '''SOL Temperature profiles using RFA in TJ-II: role of edge radial electric fields''' == Name and affiliation o..."

== Experimental campaign ==
Spring 2022

== Proposal title ==
'''SOL Temperature profiles using RFA in TJ-II: 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:Biasing probe

2021-12-01T09:09:23Z

Igor voldiner: Fixed sector reference (toroidal angle is correct)

[[File:TJ-II_Biasing_probe.jpg|300px|thumb|right|Layout of the biasing probe, mounted on the [[TJ-II:Langmuir Probes|reciprocating probe]] drive]]
At [[TJ-II]], a 2-D carbon composite mushroom shaped electrode (12 mm high with a diameter of 25 mm) has been developed and installed on a fast reciprocating probe drive. Typically, the electrode is inserted to a position 2 cm inside the last closed flux surface (LCFS) and biased positively (200-300 V) with respect to one of the two [[TJ-II:Limiter|TJ-II limiters]] located in the [[Scrape-Off Layer]] region (about 0.5 cm beyond the LCFS). Measured electrode currents are in the range of 30-50 A.

The impact of biasing on confinement properties has been studied to some depth.
<ref>C. Silva et al, ''Transport and fluctuations during electrode biasing on TJ-II'', [[doi:10.1007/s10582-006-0044-3|Czech. J. Phys. '''55''' (2005) 1589]]</ref>
<ref>M.A. Pedrosa et al, ''Transport and fluctuations during electrode biasing experiments on the TJ-II stellarator'', [http://www-pub.iaea.org/MTCD/Meetings/FEC2006/ex_p4-40.pdf Proc. 12<sup>st</sup> Fusion Energy Conf. (2006) EX-P4/40]</ref>

In 2009, the power source (originally DC) has been upgraded to allow modulation with a frequency of up to a few kHz.

Location: [[TJ-II:Sectors|sector]] A8 (φ = 174.4 °).
Signal names in the [[TJ-II:Shot_database|TJ-II database]]:
'PolI', 'PolV'.

[[File:Polarisation_probe.jpg|500px|thumb|left|Photo of the reciprocating drive of the biasing probe (top right)]]

== References ==
<references />