DOUBLE code simulations of emissivities of fast neutrals for different plasma observation view-lines of neutral particle analyzers on the COMPASS tokamak

0508697 - ÚFP 2020 RIV GB eng C - Conference Paper (international conference)
Bogár, Klára - Tomeš, Matěj - Stöckel, Jan - Varju, Jozef - Stano, M.
DOUBLE code simulations of emissivities of fast neutrals for different plasma observation view-lines of neutral particle analyzers on the COMPASS tokamak.
Journal of Physics: Conference Series. Vol. 1046. Bristol: IOP Publishing Ltd., 2018, Roč. 992, č. 1 (2018), č. článku 012009. ISSN 1742-6588.
[20th International Summer School on Vacuum, Electron and Ion Technologies. Sozopol (BG), 25.09.2017-27.09.2017]
R&D Projects: GA MŠMT(CZ) 8D15001; GA MŠMT(CZ) LM2015045
EU Projects: European Commission(XE) 633053 - EUROfusion
Institutional support: RVO:61389021
Keywords : DOUBLE * COMPASS
OECD category: Fluids and plasma physics (including surface physics)
https://iopscience.iop.org/article/10.1088/1742-6596/992/1/012009/pdf

Neutral particle analyzers (NPA) measure line-integrated energy spectra of fast neutral atoms escaping the tokamak plasma, which are a product of charge-exchange (CX) collisions of plasma ions with background neutrals. They can observe variations in the ion temperature T i of non-thermal fast ions created by additional plasma heating. However, the plasma column which a fast atom has to pass through must be sufficiently short in comparison with the fast atom's mean-free-path. Tokamak COMPASS is currently equipped with one NPA installed at a tangential mid-plane port. This orientation is optimal for observing non-thermal fast ions. However, in this configuration the signal at energies useful for T i derivation is lost in noise due to the too long fast atoms' trajectories. Thus, a second NPA is planned to be connected for the purpose of measuring T i. We analyzed different possible view-lines (perpendicular mid-plane, tangential mid-plane, and top view) for the second NPA using the DOUBLE Monte-Carlo code and compared the results with the performance of the present NPA with tangential orientation. The DOUBLE code provides fast-atoms' emissivity functions along the NPA view-line. The position of the median of these emissivity functions is related to the location from where the measured signal originates. Further, we compared the difference between the real central T i used as a DOUBLE code input and the T iCX derived from the exponential decay of simulated energy spectra. The advantages and disadvantages of each NPA location are discussed.
Permanent Link: http://hdl.handle.net/11104/0299532