A PIC-MCC code RFdinity1d for simulation of discharge initiation by ICRF antenna

M. Tripský, T. Wauters, A. Lyssoivan, V. Bobkov, P. A. Schneider, I. Stepanov, D. Douai, D. Van Eester, J. M. Noterdaeme, M. Van Schoor

Onderzoeksoutput: Bijdrage aan een tijdschriftArtikelpeer review

Samenvatting

Discharges produced and sustained by ion cyclotron range of frequency (ICRF) waves in absence of plasma current will be used on ITER for (ion cyclotron-) wall conditioning (ICWC, Te = 3-5 eV, ne < 1018 m-3). In this paper, we present the 1D particle-in-cell Monte Carlo collision (PIC-MCC) RFdinity1d for the study the breakdown phase of ICRF discharges, and its dependency on the RF discharge parameters (i) antenna input power Pi, (ii) RF frequency f, (iii) shape of the electric field and (iv) the neutral gas pressure pH2. The code traces the motion of both electrons and ions in a narrow bundle of magnetic field lines close to the antenna straps. The charged particles are accelerated in the parallel direction with respect to the magnetic field BT by two electric fields: (i) the vacuum RF field of the ICRF antenna ERFz and (ii) the electrostatic field EPz determined by the solution of Poisson's equation. The electron density evolution in simulations follows exponential increase, ṅe ∼ νiont . The ionization rate varies with increasing electron density as different mechanisms become important. The charged particles are affected solely by the antenna RF field ERFz at low electron density (ne < 1011 m-3, |ERFz|Gt;|EPz|). At higher densities, when the electrostatic field EPz is comparable to the antenna RF field ERFz, the ionization frequency reaches the maximum. Plasma oscillations propagating toroidally away from the antenna are observed. The simulated energy distributions of ions and electrons at ne ∼ 1015 m-3 correspond a power-law Kappa energy distribution. This energy distribution was also observed in NPA measurements at ASDEX Upgrade in ICWC experiments.

Originele taal-2Engels
Artikelnummer126043
TijdschriftNuclear Fusion
Volume57
Nummer van het tijdschrift12
DOI's
StatusGepubliceerd - 5 okt. 2017

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