TJ-II:Validation of bootstrap predictions - Revision history

Admin at 09:17, 27 March 2018

2018-03-27T09:17:49Z

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	[[Category:TJ-II internal documents]]		[[Category:TJ-II internal documents]]
	[[Category:TJ-II experimental proposals]]		[[Category:TJ-II experimental proposals Spring 2018]]

Ascasibar: /* Description of required resources */

2018-02-14T15:59:06Z

Description of required resources

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	We will measure:		We will measure:

	- The time evolution of the total current <math><I_t(t)></math> with the ~~Rogowsky~~ coils.		- The time evolution of the total current <math><I_t(t)></math> with the Rogowski coils.

	- Two components of the magnetic field at the end of the discharge (when <math><I_t(t)></math> has converged) with the Motional Stark Effect		- Two components of the magnetic field at the end of the discharge (when <math><I_t(t)></math> has converged) with the Motional Stark Effect

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

2018-02-14T10:55:30Z

Preferred dates and degree of flexibility

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	== Preferred dates and degree of flexibility ==		== Preferred dates and degree of flexibility ==
	Preferred dates: (format dd-mm-yyyy):		Preferred dates: (format dd-mm-yyyy): J. L. Velasco and K. J. McCarthy will be unavailable from 10th to 12th of April (CWGM). K. J. McCarthy will be unavailable from 23rd to 27th of April (W7-X) and on Thursday 17th of May (Erasmus Laboratories).

	== References ==		== References ==

Jlvelasco: /* Proposal title */

2018-02-12T19:36:41Z

Proposal title

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	== Proposal title ==		== Proposal title ==
	''~~Comparison~~ of bootstrap predictions ~~with Motional Stark Effect and Rogowski Coils~~''.		''Validation of bootstrap predictions''.

	== Name and affiliation of proponent ==		== Name and affiliation of proponent ==

Jlvelasco at 19:35, 12 February 2018

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	== Proposal title ==		== Proposal title ==
	''Comparison of bootstrap predictions with Motional Stark Effect and Rogowski Coils''		''Comparison of bootstrap predictions with Motional Stark Effect and Rogowski Coils''.

	== Name and affiliation of proponent ==		== Name and affiliation of proponent ==
	José Luis Velasco, Kieran McCarthy, Enrique Ascasíbar, Shinsuke Satake (NIFS) et al.		José Luis Velasco, Kieran McCarthy, Enrique Ascasíbar, Shinsuke Satake (NIFS) ''et al''.

	== Details of contact person at LNF (if applicable) ==		== Details of contact person at LNF (if applicable) ==
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	- The time evolution of the total current <math><I_t(t)></math> with the Rogowsky coils.		- The time evolution of the total current <math><I_t(t)></math> with the Rogowsky coils.

	- Two components of the magnetic field at the end of the discharge (when <I_t(t)> has converged) with the Motional Stark Effect		- Two components of the magnetic field at the end of the discharge (when <math><I_t(t)></math> has converged) with the Motional Stark Effect

	- The time evolution of the line-averaged density <math><n_e(t)></math> with interferometry.		- The time evolution of the line-averaged density <math><n_e(t)></math> with interferometry.
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	- The time evolution of the radial electric field in the gradient region <math>E_r(r/a~=0.65,t)</math>, with reflectometry.		- The time evolution of the radial electric field in the gradient region <math>E_r(r/a~=0.65,t)</math>, with reflectometry.


	~~- ...~~

Jlvelasco: Created page with "== Experimental campaign == 2018 Spring == Proposal title == ''Comparison of bootstrap predictions with Motional Stark Effect and Rogowski Coils'' == Name and affiliation of..."

2018-02-12T19:33:44Z

Created page with "== Experimental campaign == 2018 Spring == Proposal title == ''Comparison of bootstrap predictions with Motional Stark Effect and Rogowski Coils'' == Name and affiliation of..."

New page

== Experimental campaign ==
2018 Spring

== Proposal title ==
''Comparison of bootstrap predictions with Motional Stark Effect and Rogowski Coils''

== Name and affiliation of proponent ==
José Luis Velasco, Kieran McCarthy, Enrique Ascasíbar, Shinsuke Satake (NIFS) et al.

== Details of contact person at LNF (if applicable) ==

== Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)==
'''Motivation.'''

The bootstrap current is a neoclassical effect triggered by the radial gradients of the density and temperature in the presence of an inhomogeneous magnetic field. This current may perturb the desired magnetic configuration produced by the external coils, which is especially problematic for shearless devices, such as W7-X or TJ-II. Therefore, in order to design magnetic configurations and suitable operation scenarios, it is necessary to gain confidence on the available neoclassical predictions of bootstrap current (see e.g. <ref>Velasco 2011 PPCF</ref> and references therein). While the ion parallel flow (the ion contribution to the bootstrap current) is considered to be validated, see e.g. <ref>Arevalo 2013 NF</ref>, the electron contribution is not. Since no measurement of the electron parallel flow is available, what is left is to measure the total current or its effect on the magnetic configuration <ref>Colchin 1990 PoF, Watanabe 1995 NF, Estrada 2002 PPCF, Schmitt 2015 PoP</ref>. The proponents have participated in a recent experiment in the deuterium campaign of LHD <ref>Satake 2017 ISHW</ref>.

'''Objectives.'''

In this experiment we will create ECH plasmas with constant line-density and electron temperature during all the discharge. The working gas will be alternatively Hydrogen and Helium, and we will scan (shot-to-shot) the radial position of ECH absortion. We will measure the time evolution of the current with the Rogowski coils and two components of the magnetic field with the Motional Stark Effect diagnostic <ref>McCarthy 2015 CPP</ref>at the end of the discharge (measurements of the vacuum field will also be necessary). We will then compare the measurements with neoclassical simulations.

Off-axis heating should lead to lower electron temperatures, and use of Helium to larger effective charge. Both things should contribute to a faster equilibration of the total current and thus make the measurements easier. We will consider adding short gas puffs of impurities (e.g. N) in order to further accelerate the time evolution of the current.

== If applicable, International or National funding project or entity ==
EUROfusion WP18.S1.A2, ENE2015-70142-P

== Description of required resources ==
Required resources:
* Number of plasma discharges or days of operation: 2 day (1 H, 1 He)
* Essential diagnostic systems:

We will measure:

- The time evolution of the total current <math><I_t(t)></math> with the Rogowsky coils.

- Two components of the magnetic field at the end of the discharge (when <I_t(t)> has converged) with the Motional Stark Effect

- The time evolution of the line-averaged density <math><n_e(t)></math> with interferometry.

- The radial profiles of electron density <math>n_e(r,t_0)</math> and temperature <math>T_e(r,t_0)</math> at one time instant <math>t_0</math> with Thomson Scattering (TS) and the He beam.

- The time evolution of the electron temperature profile <math>T_e(r,t)</math> with Electron Cyclotron Emission (ECE), when available, calibrated with TS.

- The time evolution of the ion temperature in the core and in an outer radial position, <math>T_i(r/a=0.2,t)</math> and <math>T_i(r/a~=0.6,t)</math>, with the Neutral Particle Analyzer (NPA).

- The time evolution of the radial electric field in the gradient region <math>E_r(r/a~=0.65,t)</math>, with reflectometry.

- ...

* Type of plasmas (heating configuration): ECH plasmas with constant line-averaged density and electron temperature as measured by ECE. We will scan the position of one of the gyrotrons in order to change the electron temperature profile.
* Specific requirements on wall conditioning if any: Lithium coating if considered necessary for stable plasmas
* 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 />

See also

http://fusionsites.ciemat.es/jlvelasco/files/notes/ICasal_informe.pdf

and

http://fusionsites.ciemat.es/jlvelasco/files/presentations/velasco_etal_bootstrap.pdf

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