Bi-Maxwellian electron energy distribution function in the vicinity of the last closed flux surface in fusion plasma

0453276 - ÚFP 2016 RIV GB eng J - Journal Article
Popov, T.S.V.K. - Dimitrova, Miglena - Pedrosa, M. A. - López-Bruna, D. - Horáček, Jan - Kovačič, J. - Dejarnac, Renaud - Stöckel, Jan - Aftanas, Milan - Böhm, Petr - Bílková, Petra - Hidalgo, C. - Pánek, Radomír
Bi-Maxwellian electron energy distribution function in the vicinity of the last closed flux surface in fusion plasma.
Plasma Physics and Controlled Fusion. Roč. 57, č. 11 (2015), č. článku 115011. ISSN 0741-3335. E-ISSN 1361-6587
R&D Projects: GA ČR(CZ) GAP205/12/2327; GA MŠMT(CZ) LM2011021
Institutional support: RVO:61389021
Keywords : COMPASS tokamak, parallel power flux density * TJ-II stellarator * bi-Maxwellian EEDF * last closed flux surface * SOL * parallel power flux density
OECD category: Fluids and plasma physics (including surface physics)
Impact factor: 2.404, year: 2015

The first-derivative probe technique was applied to derive data for plasma parameters from the IV Langmuir probe characteristics measured in the plasma boundary region in the COMPASS tokamak and in the TJ-II stellarator. It is shown that in the COMPASS tokamak in the vicinity of the last closed flux surface (LCFS) the electron energy distribution function (EEDF) is bi-Maxwellian with the low-temperature electron fraction predominating over the higher temperature one, whereas in the far scrape-off layer (SOL) the EEDF is Maxwellian. The mechanism for the appearance of a bi-Maxwellian EEDF in the vicinity of the LCFS is discussed. The comparison of the results from probe measurements with ASTRA package and EIRENE code calculations suggests that the main reason of the appearance of a bi-Maxwellian EEDF in the vicinity of the LCFS is the ionization of the neutral atoms. It is shown that in the SOL the radial distribution of the parallel power flux density is a double exponential.
Permanent Link: http://hdl.handle.net/11104/0254110