Speaker
Nathaniel Joseph Fisch
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P4.1064.pdf
Conferenceonon Plasma
Plasma Physics,
Physics 2018, Prague, Czech Republic P4.1064
Synchrotron spectra, images, and polarization measurements from
runaway electrons in the Alcator C-Mod tokamak
R.A. Tinguely1, R.S. Granetz1, M. Hoppe2, O. Embréus2, and T. Fülöp2
1
Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, USA
2
Department of Physics, Chalmers University of Technology, Göteborg, Sweden
In the high-field, compact Alcator C-Mod tokamak, relativistic runaway electrons (REs)
generated during flattop plasma discharges emit synchrotron radiation in the visible
wavelength range. Thus, spectrometers, cameras, and the Motional Stark Effect diagnostic
installed on C-Mod measure absolutely-calibrated spectra, distortion-corrected images, and
polarization information, respectively, of REs throughout the plasma. Due to the complex
interplay of the RE phase-space distribution, plasma magnetic topology, and detector geometry,
the synthetic diagnostic SOFT [1] is used to simulate all three measurements and compare
theory with experiment. As inputs, the RE momenta and density distributions are calculated
using both a test-particle model [2 – 4] and kinetic solver CODE [5]. In particular, this work
explores the following: (1) Synchrotron spectra observed from REs generated at three magnetic
fields (B0 = 2.7, 5.4, and 7.8 T) indicate a decrease in RE energy as synchrotron power loss is
enhanced at higher fields [6]. (2) Transport and MHD activity are incorporated into the analysis
of synchrotron images to better explain interesting spatiotemporal features. (3) Profiles of
linearly-polarized synchrotron emission intensity and polarization angle are explored as a novel
diagnostic of RE dynamics.
[1] M. Hoppe, et al., Nucl. Fusion 58 (2018).
[2] J.R. Martín-Solís, et al., Phys. Plasmas 5 (1998).
[3] J.W. Connor and R.J. Hastie, Nucl. Fusion 15 (1975).
[4] M.N. Rosenbluth and S.V. Putvinski, Nucl. Fusion 37 (1997).
[5] M. Landreman, et al., Comput. Phys. Commun. 185 (2014).
[6] R.A. Tinguely, et al., submitted to Nucl. Fusion (2018).
This work is supported by the US DOE (grant DE-FC02-99ER54512), using Alcator C-Mod, a DOE Office of
Science User Facility; Vetenskapsrådet (Dnr 2014-5510); and the European Research Council (ERC-2014-CoG
grant 647121).
