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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 17:20, 12 February 2018
, 12 February 2018→Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)
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== Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)== | == Description of the activity, including motivation/objectives and experience of the proponent (typically one-two pages)== | ||
Suprathermal ions have been detected using optical spectroscopy techniques in TJ-II | 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 [2]. 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 [3] 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. | ||
In the shot plotted in figure 1 the NPA was tuned to 200 eV in the lowest energy channel. As can be seen, the count rate in the lower energy channels (NPA 01 – NPA 06, 200 eV to 446 eV) dropped, as did the Halpha signal. In contrast, in the higher energy channels (NPA 07 – NPA 09, 540 eV to 826 eV) the count rate fell when the gyrotron was turned off. This can be a indication of the existence of suprathermal ions. The amount of suprathermal ions depends on the position of the plasma heating, so not all discharges presented the same behaviour. | In the shot plotted in figure 1 the NPA was tuned to 200 eV in the lowest energy channel. As can be seen, the count rate in the lower energy channels (NPA 01 – NPA 06, 200 eV to 446 eV) dropped, as did the Halpha signal. In contrast, in the higher energy channels (NPA 07 – NPA 09, 540 eV to 826 eV) the count rate fell when the gyrotron was turned off. This can be a indication of the existence of suprathermal ions. The amount of suprathermal ions depends on the position of the plasma heating, so not all discharges presented the same behaviour. | ||