Determination of the plasma potential and the EEDF by Langmuir probes in the divertor region of COMPASS tokamak

6th International Workshop & Summer School on Plasma Physics 2014

Ivanova, P.^1 ; Dimitrova, M.^1,2 ; Vasileva, E.^1 ; Popov, Tsv K^3 ; Dejarnac, R.^2 ; Stockel, J.^2 ; Imrífsek, M.^2 ; Hacek, P.^2 ; Panek, R.^2

Acad. E. Djakov Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chaussee, Sofia

1784, Bulgaria^1

Institute of Plasma Physics, Academy of Sciences of the Czech Republic, V.v.i., 3 Za Slovankou, Prague 8

182 00, Czech Republic^2

Faculty of Physics, St. Kl. Ohridski University of Sofia, 5 J. Bourchier Blvd., Sofia

1164, Bulgaria^3

关键词: Discharge conditions;    Electron energy distribution functions;    Low energy electrons;    Maxwellian distribution;    Measured currents;    Precise determinations;    Private-flux regions;    Toroidal magnetic fields;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/768/1/012003/pdf
DOI  :  10.1088/1742-6596/768/1/012003

来源: IOP

【 摘 要 】

This paper reports experimental data obtained on the COMPASS tokamak by an array of Langmuir probes embedded in the divertor tiles. The measured current-voltage probe characteristics were processed by the recently published first-derivative probe technique for precise determination of the plasma potential and the electron energy distribution function (EEDF). The measurements were performed during L-mode hydrogen and deuterium plasma with a toroidal magnetic field Bt = 1.15 T, plasma current Ip = 180 kA and average electron density ne = 8∗1019m-3. The spatial profile of the electron temperatures shows that in the vicinity of the inner and outer strike points in hydrogen plasma the EEDF can be approximated by a bi-Maxwellian distribution, with a dominating low-energy electron population (4 - 7 eV) and a minority of electrons with higher energies (12 - 18 eV). In the private flux region between the two strike points, the EEDF is found to be Maxwellian with temperatures in the range of 7 - 9 eV. In the case of deuterium plasma under similar discharge conditions, the EEDFs in the vicinity of the inner and outer strike points, as well as in the private flux region between the two strike points, are found to be bi-Maxwellian.