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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
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TJ-II:Observation of suprathermal ions with Neutral Particle Analyzers during electron cyclotron heating in the TJ-II stellarator (view source)
Revision as of 16:18, 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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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. | ||
[[File:NPA42626.png]] | [[File:NPA42626.png |1200px]] | ||
A possible explanation for the suprathermal ions is a parametric decay of the injected waves [4]. 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 [4]. In order for this to occur, a hollow profile of the density is necessary, as in TJ-II ECR heated plasmas. | ||