Speaker
Michal Farník
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P1.1010.pdf
Runaway electron diagnostics for the COMPASS tokamak using EC
emission
M. Farnik1,2 , J. Urban1 , J. Zajac1 , O. Bogar1,3 , O. Ficker1,2 , E. Macusova1 , J. Mlynar1,2 ,
J. Cerovsky1,2 , M. Varavin1 , V. Weinzettl1 , M. Hron1 and the COMPASS team1
1 Institute of Plasma Physics of the CAS, Prague, Czech Rep.
2 FNSPE, Czech Technical University, Prague, Czech Rep.
3 FMPI, Comenius University in Bratislava, Bratislava, Slovakia
Electron cyclotron emission measured vertically along the line of a constant magnetic field
can yield information about the electron velocity distribution function and its evolution during a
discharge [1]. A vertical ECE (V-ECE) diagnostic is available on COMPASS, a compact-sized
tokamak operated at IPP Prague. We report on results from this diagnostic during runaway
electron (RE) experiments.
The V-ECE diagnostic on COMPASS consists of a 16-channel radiometer E-band horn an-
tenna with a 76.5 - 88.3 GHz frequency range front-end. Simulations using the SPECE ray-
tracing code [2] have aided the final diagnostic design and are employed for experimental data
interpretation. Realised measurements of extraordinary and ordinary mode (X/O mode) in low-
density (ne < 3 · 1019 m−3 ) RE experiments will be presented. The detected signal can be at-
tributed to the 3rd harmonic emission from 50 - 140 keV electrons. However, the optical depth
is rather low, which complicates the measured data interpretation.
V-ECE measurements in low-density flattop discharges and in discharges with massive gas
injections (MGI) of high-Z elements show correlations with other RE diagnostics, such as hard
X-rays (HXR), photoneutron detectors and high-speed visible light cameras. Our results seem
to be in an agreement with the principles of the primary runaway generation mechanisms.
References
[1] K. Kato, I. H. Hutchinson, Phys. Rev. Lett. 56(4) 340-343 (1986)
[2] D. Farina, et al., AIP Conf. Proceedings 988 128-131 (2010)
