RF plasma simulations using the TOMATOR 1D code: A case study for TCV helium ECRH plasmas

T. Wauters (Corresponding Author), J. Buermans, R. Haelterman, V. Moiseenko, D. Ricci, T. Verhaeghe, S. Coda, D. Douai, A. Hakola, A. Lyssoivan, D. Van Eester

Research output: Contribution to journalArticleScientificpeer-review

Abstract

The 1-dimensional reaction-diffusion-convection code TOMATOR-1D describes plasma production by RF waves inside a tokamak using the Braginskii continuity and heat balance equations. The model simulates self-consistent radial density and temperature profiles for magnetised plasma mixtures of hydrogen and helium. The model reproduces the density profiles of X2 electron cyclotron resonance heating (ECRH) plasmas on TCV and proposes a Bohm-like poloidal magnetic field dependent scaling for anomalous diffusion and a convection scaling that results from drifts in the toroidal magnetic field configuration. A relation is proposed between the anomalous diffusion and the outward convection in toroidal plasmas. It is found that the EC absorption efficiency decreases at higher power, which is understood from the acceleration of electrons beyond the optimal energy for the electron impact ionisation of helium. A dramatic increase of the absorption efficiency is seen at intermediate vertical magnetic field values of Bz = 0.25%â'0.5%BT which results in the highest density plasmas. Losses along the field lines in the vertical direction become dominant at higher fields which effectively reduces the plasma density in these discharges. To arrive at predictive capabilities towards ECRH plasmas on JT-60SA and ITER, the proposed scalings, subsuming dependencies on the torus major radius and the toroidal field strength, need to be validated in a multi-machine study.

Original languageEnglish
Article number105010
Number of pages8
JournalPlasma Physics and Controlled Fusion
Volume62
Issue number10
DOIs
Publication statusE-pub ahead of print - 20 Aug 2020
MoE publication typeA1 Journal article-refereed

Keywords

  • ECRH
  • ECWC
  • Plasma start-up
  • TCV
  • Tokamak
  • Wall conditioning

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