ELM temperature in JET and COMPASS tokamak divertors

0572762 - ÚFP 2024 RIV US eng J - Článek v odborném periodiku
Horáček, Jan - Tskhakaya, David - Cavalier, Jordan - Adámek, Jiří - Mana, A. C. - Frassinetti, L. - Beltrami, A. - Lukeš, S. - Aleiferis, S. - Matthews, G. - Komm, Michael - Bílková, Petra
ELM temperature in JET and COMPASS tokamak divertors.
Nuclear Fusion. Roč. 63, č. 5 (2023), č. článku 056007. ISSN 0029-5515. E-ISSN 1741-4326
Grant CEP: GA ČR(CZ) GA22-03950S; GA ČR(CZ) GA20-28161S
GRANT EU: European Commission(BE) 101052200
Institucionální podpora: RVO:61389021
Klíčová slova: divertor * plasma * temperature * tokamak
Obor OECD: Fluids and plasma physics (including surface physics)
Impakt faktor: 3.3, rok: 2022
Způsob publikování: Open access
https://iopscience.iop.org/article/10.1088/1741-4326/acbf68

Analysis of the divertor edge localized mode (ELM) electron temperature at a uniquely high temporal resolution (10−5 s) was reported at the JET tokamak (Guillemaut et al 2018 Nucl. Fusion 58 066006). By collecting divertor probe data obtained during many dozens of ELMs, the conditional-average (CAV) technique yields surprisingly low peak electron temperatures, far below the pedestal ones (70%-99% reduction!) which we, however, question. This result was interpreted through the collisional free-streaming kinetic model of ELMs, by a transfer of most of the electron energy to ions, implying a high tungsten sputtering for unmitigated ELMs in future fusion devices like ITER. Recently, direct microsecond temperature measurements on the COMPASS tokamak, however, showed that the electron temperature peak of ELM filaments measured in the divertor is reduced by less than a third with respect to the pedestal one. This was further confirmed by a dedicated 1D particle-in-cell (PIC) simulation and tends to prove that the pedestal electrons can transfer only their parallel energy to ions (due to low collisionality), thus less than a third, as is predicted by the collisionless free-streaming model. This finding strongly contradicts the JET observations. We have therefore compared the CAV to the direct (microsecond) ball-pen and Langmuir probes measurements in COMPASS and found very good agreement between them. Revisiting the aforementioned JET CAV analysis indeed shows that the electron temperatures are much higher than previously reported, close to those predicted by the PIC simulation, and thus the ion energy seems to not significantly increase in the scrape-off layer.
Trvalý link: https://hdl.handle.net/11104/0343334