ELM temperature in JET and COMPASS tokamak divertors

Nuclear Fushion

article

J. Horacek¹  D. Tskhakaya¹  J. Cavalier¹  J. Adamek¹  A.C. Mana²  L. Frassinetti³  A. Beltrami⁴  S. Lukes⁵  S. Aleiferis⁶  G. Matthews⁶  M. Komm¹  P. Bilkova¹ 

[1] Institute of Plasma Physics of the CAS;Institut Jean Lamour, University of Lorraine;Division of Fusion Plasma Physics;University of Milano-Bicocca;Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University;CCFE, Culham Science Centre Abingdon OX14 3DB

关键词: tokamak;    divertor;    plasma;    temperature;   

DOI  :  10.1088/1741-4326/acbf68

来源: Institute of Physics Publishing Ltd.

【 摘 要 】

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 (Guillemautet al2018Nucl. Fusion58066006). 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 theirparallelenergy to ions (due to low collisionality), thus less than a third, as is predicted by thecollisionlessfree-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.

【 授权许可】

Unknown