Temporal characteristics of ELMs on the COMPASS divertor

0574103 - ÚFP 2024 RIV US eng J - Journal Article
Adámek, Jiří - Cavalier, Jordan - Tskhakaya, David - Csillag, B. - Cinnirella, L. - Lips, J. - Lopez-Rodriguez, D. - Sosa, D. - Medina, D. - Vondráček, Petr - Kripner, Lukáš - Komm, Michael - Šos, Miroslav - Lindl, H.
Temporal characteristics of ELMs on the COMPASS divertor.
Nuclear Fusion. Roč. 63, č. 8 (2023), č. článku 086009. ISSN 0029-5515. E-ISSN 1741-4326
R&D Projects: GA MŠMT(CZ) EF16_013/0001551; GA ČR(CZ) GA20-28161S
Institutional support: RVO:61389021
Keywords : compass * divertor * elm * temporal characteristics * tokamak
OECD category: Fluids and plasma physics (including surface physics)
Impact factor: 3.3, year: 2022
Method of publishing: Open access
https://iopscience.iop.org/article/10.1088/1741-4326/acdd10

The presented work shows a systematic study of the temporal characteristics of ELM events on the COMPASS divertor obtained with high temporal resolution probe measurements (∼1 μs). The resulting temporal evolution of the total ELM power on the outer target provides the values of rise (τ rise) and decay (τ decay) times for each single ELM event. It has been found that τ rise values are in the range of about 50 μs-100 μs. These values are comparable to the time of the ELM parallel propagation (τ ||) given by the sound speed and the connection length between the outer midplane and the outboard divertor. This comparison indicates that the magnetic field lines in the SOL region are not significantly ergodized during the pedestal crash on COMPASS. It also implies that the peak ELM energy fluence on the outboard divertor is dominated by the ELM parallel transport, which is confirmed by a good agreement with model prediction. In addition, the values of the ratio of τ decay and τ rise for each ELM event fit very well to the boundaries 1.5 < τ decay/τ rise < 4, as already shown on JET as well as on the HL-2A tokamak, using IR measurements. The ratio does not show any clear dependence on the relative ELM energy or line averaged electron density. It was also found that the ELM energy fluence decay length (λϵmid) is clearly linked to this ratio.
Permanent Link: https://hdl.handle.net/11104/0344459