Temporal characteristics of ELMs on the COMPASS divertor

Nuclear Fushion

article

J. Adamek¹  J. Cavalier¹  D. Tskhakaya¹  B. Csillag²  L. Cinnirella³  J. Lips⁴  D. Lopez-Rodriguez⁵  D. Sosa⁶  D. Medina⁶  P. Vondracek¹  L. Kripner¹  M. Komm¹  M. Sos¹  H. Lindl³ 

[1] Institute of Plasma Physics of the Czech Academy of Sciences;Centre for Energy Research;Max–Planck-Institut für Plasmaphysik;University of Stuttgart, Institute of Combustion and Power Plant Technology;Laboratory for Plasma Physics of the Ecole Royale Militaire;Laboratorio Nacional de Fusión

关键词: ELM;    tokamak;    COMPASS;    divertor;    temporal characteristics;   

DOI  :  10.1088/1741-4326/acdd10

来源: Institute of Physics Publishing Ltd.

【 摘 要 】

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 (∼1μ s). 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 thatτ _rise values are in the range of about 50μ s–100μ s. 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 ofτ _decay andτ _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 ( λ ^mid) is clearly linked to this ratio.

【 授权许可】

Unknown