Speaker
Ondrej Ficker
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P1.1062.pdf
Analysis of MGI disruptions and runaway electron beams
at COMPASS using tomography and fast camera data
O. Ficker1,2 , M. Imrisek 1,3 J. Mlynar1 , E. Macusova1 , J. Svoboda2 , V. Weinzettl1 , J. Urban1
J. Cerovsky1,2 , M. Farnik1,2 , V. Plyusnin5 , R. Panek1 , M. Hron1 , M. Vlainic4
the COMPASS team1 & the EUROfusion MST1 Team*
1 Institute of Plasma Physics of the CAS, Prague, Czech Republic
2 FNSPE, Czech Technical University in Prague, Prague, Czech Republic
3 Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic
4 Institute of Physics, University of Belgrade, Belgrade, Serbia
5 IST - IPFN, Lisbon, Portugal
* See the author list "H. Meyer et al 2017 Nucl. Fusion 57 102014"
The tomographic inversion of signals from SXR and AXUV detector arrays is a valuable tool
in various operational scenarios on COMPASS. However, runaway electron (RE) beam genera-
tion and mitigation experiments conducted at COMPASS [1] present a challenge to this method
as this scenario creates a very noisy environment and conditions far from the optimal design
parameters of the detectors. The massive gas injection, subsequent disruption and RE beam
generation and decay phases are a source of quickly changing intensities of radiation in a broad
range of wavelengths (bremsstrahlung and line radiation of the gas atoms and ions). In particu-
lar, the semiconductor-based detectors are also strongly affected by the HXR radiation produced
due to the interaction of relativistic electrons with the wall. On the other hand, the tomographic
inversion in this scenario might be a valuable source of information about the gas penetration
speed, beam position, total radiated power and profile of the beam-gas interaction which might
be related to the beam current profile or electron energy. Values of some of these quantities, in
particular the ones related to the gas transport, can be also derived from high-speed camera im-
ages that are usually only weakly affected by the HXR radiation. This contribution summarizes
the difficulties of using tomography in this scenario and the different effect of various mitigation
gases (Ar, Ne, D) on the radiation signals, including the high-speed camera data.
References
[1] Mlynar J. et al, invited, this conference
[2] Panek R. et al. 2016 Plas. Phys. Contr. Fusion 58 014015
[3] Vlainic M. et al. 2015 J. Plasma Phys. 81 475810506
