EPJ Web of Conferences (Jan 2019)

Runaway electron diagnostics for the COMPASS tokamak using EC emission

  • Farnik Michal,
  • Urban Jakub,
  • Zajac Jaromir,
  • Bogar Ondrej,
  • Ficker Ondrej,
  • Macusova Eva,
  • Mlynar Jan,
  • Cerovsky Jaroslav,
  • Varavin Mikita,
  • Weinzettl Vladimir,
  • Hron Martin

DOI
https://doi.org/10.1051/epjconf/201920303006
Journal volume & issue
Vol. 203
p. 03006

Abstract

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An electron cyclotron emission (ECE) diagnostic of suprathermal electrons was utilised for runaway electron (RE) experiments purposes in the COMPASS tokamak. Our vertical ECE (V-ECE) system consists of a 16-channel heterodyne radiometer and an E-band horn antenna with a 76.5-88 GHz frequency range front-end. Simulations used for the design of the diagnostic showed a possibility of detecting the emission of low-energy (50-140 keV) runaway electrons. We realized measurements with both extraordinary (X-) and ordinary (O-) mode linear polarizations. The amplitudes of the X-mode and O-mode signals are similar, which can be explained by depolarised reflected radiation. V-ECE measurements in low-density flattop discharges and in discharges with massive gas injections of high-Z elements show correlations with other RE diagnostics. Our results are in the agreement with the principles of the primary runaway generation mechanisms.