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#40
Runaway electron distribution reconstruction using multispectral synchrotron camera imaging in TCV Oral
Tijs Wijkamp (Eindhoven University of Technology)
A. Perek, J. Decker, B. Duval, M. Hoppe, G. Papp, U.A. Sheikh, I.G.J. Classen, R.J.E. Jaspers, the TCV Team and the EUROfusion WPTE Team
SCHEDULED This contribution is scheduled to be presented on Thursday 5th 11:15-11:45
Abstract
In quiescent Tokamak à Configuration Variable (TCV) discharges, filtered camera imaging of synchrotron radiation is used to determine the distribution in momentum- and real space of the runaway electrons at highest energies and pitch angles [1]. The synthetic synchrotron camera diagnostic SOFT [2] is used to construct a pixel dependent response function to runaway phase space. This facilitates inference of the distribution from experimental images acquired for three different narrowband wavelength intervals in the visible through a tomographic reconstruction procedure. The part of the population contributing most to the synchrotron radiation is estimated to have energies near 30 MeV and pitch angles exceeding 0.5 radians, consistent with an earlier super-particle estimate [3]. One hypothesis as to why there is a significant population at these pitch angles is that the runaways are scattered through resonant interaction with the magnetic field ripple. The edge-peaked shape of the inferred distribution is in line with this hypothesis, as the effective ripple strength grows with increasing minor radius. Potential application of multispectral imaging systems in characterization of runaway filled post-disruptive background plasmas is briefly touched upon. The approach for setting bounds on 2D (R,Z) electron temperature and impurity density profiles is discussed. Impurity profiles can for instance help to narrow down estimates of the Ne/D2 ratios in D2 injection aided benign termination experiments. Electron density and temperature bounds can be used as constraints in power balance studies to better understand post-disruptive plasma behavior. [1] T.A. Wijkamp et al 2021 Nucl. Fusion 61 046044 [2] M. Hoppe et al 2018 Nucl. Fusion 58 026032 [3] M. Hoppe et al 2020 Nucl. Fusion 60 094002
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