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TJ-II:Observation of suprathermal ions with Neutral Particle Analyzers during electron cyclotron heating in the TJ-II stellarator: Difference between revisions
TJ-II:Observation of suprathermal ions with Neutral Particle Analyzers during electron cyclotron heating in the TJ-II stellarator (view source)
Revision as of 11:26, 29 January 2019
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== Experimental campaign == | == Experimental campaign == | ||
2019 Spring | |||
== Proposal title == | == Proposal title == | ||
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N/A | N/A | ||
== Description of the activity, including motivation/objectives | == Description of the activity, including motivation/objectives == | ||
Suprathermal ions have been detected using optical spectroscopy techniques in TJ-II <ref> Rapisarda et al. Plasma Phys. Control. Fusion '''49''' 309 (2007). </ref> but without conclusive results when using NPA diagnostics <ref> Fontdecaba et al. Review of Scientific Instruments '''85''' 11E803 (2014). </ref>. One experiment of the 2016 campaign, designed to investigate this population, consisted in operating one gyrotron along all the discharge while modulating the second gyrotron at 100% of its power <ref> Zurro et al. 44thEPS Conference on Plasma Physics P1.145 (2017).</ref> and changing the power deposition position in a shot-to-shot basis. No neutral beam power was injected. When both gyrotrons were on an indication of suprathermal ions was observed by the NPA diagnostic, see figure 1. | Suprathermal ions have been detected using optical spectroscopy techniques in TJ-II <ref> Rapisarda et al. Plasma Phys. Control. Fusion '''49''' 309 (2007). </ref> but without conclusive results when using NPA diagnostics <ref> Fontdecaba et al. Review of Scientific Instruments '''85''' 11E803 (2014). </ref>. One experiment of the 2016 campaign, designed to investigate this population, consisted in operating one gyrotron along all the discharge while modulating the second gyrotron at 100% of its power <ref> Zurro et al. 44thEPS Conference on Plasma Physics P1.145 (2017).</ref> and changing the power deposition position in a shot-to-shot basis. No neutral beam power was injected. When both gyrotrons were on an indication of suprathermal ions was observed by the NPA diagnostic, see figure 1. | ||
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A possible explanation for the suprathermal ions is a parametric decay of the injected waves <ref> E.Z Gusakov and A. Yu. Popov Plasma Phys. Comtrol. Fusion '''60''' 025001 (2018)</ref>. In order for this to occur, a hollow profile of the density is necessary, as in TJ-II ECR heated plasmas. | A possible explanation for the suprathermal ions is a parametric decay of the injected waves <ref> E.Z Gusakov and A. Yu. Popov Plasma Phys. Comtrol. Fusion '''60''' 025001 (2018)</ref>. In order for this to occur, a hollow profile of the density is necessary, as in TJ-II ECR heated plasmas. | ||
In this proposal we want to reproduce the results of the 2016 campaign and in addition, change the position of the NPA in order to check the radial extension of the suprathermal ion population. Also it is intended to inject hydrogen pellets at suitable moments along the discharge in order to change the density profile, i.e. to test the validity of the assumption in [4] of the necessity of a local maximum of a non-monotonous density profile to produce the parametric decay. | In this proposal we want to reproduce the results of the 2016 campaign and in addition, change the position of the NPA in order to check the radial extension of the suprathermal ion population. Also it is intended to inject hydrogen pellets at suitable moments along the discharge in order to change the density profile, i.e. to test the validity of the assumption in [4] of the necessity of a local maximum of a non-monotonous density profile to produce the parametric decay. | ||
'''New 29/01/2019''' The heating position will be changed in order to find the maximum flux of suprathermal ions. Once found, a power scan will be performed to find the minimum power for triggering the production of suprathermals. | |||
The discharges would be similar to those of the 17/11/2016 shots between 42617 and 42647 with one gyrotron heating along all the discharge and the other modulated 100 % with 20 ms period. In one of the phases with both gyrotrons on the pellet will fire so the density profile will change. The difference on the NPA signal will show the presence or not of suprathermal ion population in each phase of the discharge. | The discharges would be similar to those of the 17/11/2016 shots between 42617 and 42647 with one gyrotron heating along all the discharge and the other modulated 100 % with 20 ms period. In one of the phases with both gyrotrons on the pellet will fire so the density profile will change. The difference on the NPA signal will show the presence or not of suprathermal ion population in each phase of the discharge. | ||
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Experiment | Experiment | ||
* ECRH plasmas with two gyrotrons, one of them modulated 100%. | * ECRH plasmas with two gyrotrons, one of them modulated 100%. Later a power scan. | ||
* NPA to look for the suprathermal ions. | * NPA to look for the suprathermal ions. | ||
* Pellet injector to change the density profile. | * Pellet injector to change the density profile. | ||
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**Pellet injector to change the density profile. | **Pellet injector to change the density profile. | ||
**Thomson scattering to measure the density profiles. | **Thomson scattering to measure the density profiles. | ||
* Type of plasmas (heating configuration):ECRH, one gyrotron modulated. | * Type of plasmas (heating configuration):ECRH, one gyrotron modulated and power scan. | ||
* Specific requirements on wall conditioning if any: | * Specific requirements on wall conditioning if any: | ||
* External users: need a local computer account for data access: no | * External users: need a local computer account for data access: no | ||
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== Preferred dates and degree of flexibility == | == Preferred dates and degree of flexibility == | ||
Preferred dates: ( | Preferred dates: (dates depend on JET campaign) | ||
March 2019. | |||
Best dates: 10-17 March (tentative). | |||
== References == | == References == | ||
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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]] | ||