Speaker
Long Zeng
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P2.1047.pdf
Dynamic evolution of runaway electron energy distribution during tokamak
disruptions
L. Zeng1, Y. Liang1, 2, H.R. Koslowski2, S. Lin1, B. Zhang1, X. Zhu1, T. Tang1, R. Zhou1, H. Liu1,
J. Qian1, S. Zhang1, Y. Jie1, X. Gong1, X. Gao1
1
Institute of Plasma Physics, Chinese Academy of Sciences, 230031 Hefei, China
2
Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research -Plasma Physics
(IEK-4), Association EURATOM-FZJ, 52425 Jülich, Germany
E-mail: zenglong@ipp.ac.cn
The dynamics of runaway electron energy distribution during tokamak disruptions is described
by a 0D model taking collision, bremsstrahlung, synchrotron radiation and also electric field into
account. It is shown that the collision term is sensitive to the low energy range of runaway
electrons but the bremsstrahlung and synchrotron radiation terms are more effective on the high
energy runaway electrons. Contribution from the external electric field mainly affect the
relatively medium energy runaways. This model introduces new features in the test equations
describing dynamic evolution of runaway electron energy distribution:
1) During massive gas injection into post-disruption runaway electron plateaus, it is shown
that for a massive injection of a low-Z gas such as helium and hydrogen to the RE beam
generated by argon injection during the disruptions, the dependence of bremsstrahlung on
the injection amount is non-monotonous. When the injection amount is less than a
threshold, the bremsstrahlung will decrease and then the maximum RE energy increase,
which can even improve RE generation. For a massive injection of a medium-Z gas such
as neon and argon, the bremsstrahlung will increase continually leading to more RE losses
and a decrease of the maximum RE energy.
2) During a large negative loop voltage applied on post-disruption runaway electron plateaus,
it is shown that the electric field de-accelerates REs and mainly decrease the RE energy in
the medium-energy range. When the added electric field is large enough, it can possibly
drive an energetic electron instability, causing the anomalous runaway losses.
