Speaker
Jose Ramon Martin-Solis
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P1.1042.pdf
A SIMPLIFIED APPROACH TO THE PHYSICS OF
RUNAWAY ELECTRON BEAM DISSIPATION IN
TOKAMAK DISRUPTIONS∗
J. R. Martin-Solis 1 , E.M. Hollmann 2 , M. Lehnen 3 and A. Loarte 3
1 Universidad
Carlos III de Madrid, Avda.Universidad 30, Leganes, 28911-Madrid, Spain.
2 University
of California-San Diego, La Jolla, California 92093-0417, USA.
3 ITER Organization, Route Vinon sur Verdon, CS90046 13067 St. Paul-lez-Durance,
France.
ABSTRACT
The injection of large amounts of high-Z impurities by Massive Gas Injection (MGI)
or Shattered Pellet Injection (SPI) constitutes the most promising candidate for the
mitigation of runaway electrons during disruptions in large devices like ITER [1,2].
In this paper, the dissipation and decay of the runaway current by injection of high-Z
impurities during tokamak disruptions is analyzed using a simplified approach, based
on the kinetic treatment of Ref. [3], which includes the effect of the collisions with the
plasma particles and the impurity ions, the synchrotron radiation losses associated with
the pitch angle scattering of the runaway electrons when colliding with the impurity
atoms as well as the bremsstrahlung radiation. The model allows to get simple estimates
of the runaway current duration, the runaway distribution function and energy during
the dissipation phase. A comparison of the effects associated with the different runaway
loss mechanisms (collisions, synchrotron and bremsstrahlung radiation losses) will be
presented . Extrapolations to ITER indicate that injection of a few kPa · m3 of Ar
could be a promising scenario for runaway electron dissipation during disruptions if
the impurities can be efficiently delivered into the plasma. Effects associated with the
runaway scraping-off due to the VDE of the runaway beam during the decay of the
current will be also considered.
[1] E.M. Hollmann et al., Phys.Plasmas 22, 021802 (2015).
[2] M. Lehnen et al., J. Nucl. Mater. 3948, 463 (2015).
[3] P. Aleynikov and B.N. Breizman, Phys.Rev.Lett. 114, 155001 (2015).
∗
This work was carried out with financial support from Dirección General de Investigación,
Cientı́fica y Técnica, Project No. ENE2015-66444-R (MINECO/FEDER, UE). ITER is the
Nuclear Facility INB no. 174. This paper explores physics processes during the plasma
operation of the tokamak when disruptions take place; nevertheless the nuclear operator is
not constrained by the results of this paper. The views and opinions expressed herein do not
necessarily reflect those of the ITER Organization.
