Speaker
Jernej Kovacic
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P1.1107.pdf
Studying the parallel dynamics of a train of blobs in a SOL of a
medium-size tokamak using particle-in-cell simulations
J. Kovačič1 , S. Costea2 , D. Tskhakaya3,4 , I. Gomez1 , T. Gyergyek1,5 , Tsv. K. Popov6 , R. Schrittwieser2
1 Jožef Stefan Institute, Ljubljana, Slovenia
2 Institute for Ion Physics and Applied Physics, University of Innsbruck, Austria
3 Institute of Applied Physics, Vienna University of Technology, Austria
4 Andronikashili Institute of Physics, Tbilisi, Georgia
5 University of Ljubljana, Faculty of Electrical Engineering, Slovenia
6 University of St. Kliment Ohridski, Faculty of Physics, Sofia, Bulgaria
The filamentary transport in the SOL has since long been a hot topic in fusion research, be-
cause of its importance to the evaluation of the first wall heat loads [1]. The filaments cross the
separatrix at outer midplane and intend to propagate in radial direction toward the wall. How-
ever, since the parallel conductivity is much higher then the perpendicular, they usually connect
to divertor in parallel direction. The phenomena is intrinsically of kinetic nature, since the fil-
aments (blobs) protruding into the SOL are significantly denser and several times hotter than
the SOL plasma. The blobs arrive into SOL with irregularity in size and waiting times, however
nowadays we have very good statistical description of such transport. What is missing is the
understanding of the parallel and radial dynamics of blobs from kinetic perspective, taking into
account the temporal development of local velocity distribution functions, which are influenced
by many different particle-particle and particle-wall interactions.
In our work we have continued with the simulation of parallel blob dynamics inside a single
flux tube of a medium-sized tokamak employing a 1d3v massively-parallel fully-kinetic code
BIT1 [2], which includes a 2d3v module for neutral particle pusher. We have modified the code
in a way, that it forms a repetitive source of blobs - a train of blobs - at the location of outer
midplane. Furthermore, an additional constant source was added, mimicking cross-field diffu-
sion. We also made cases with inclusion of recycling at the divertor plates, which extended our
research into interaction of fast blob particles with the neutrals. In the simulations the domain
is initially empty, and the SOL is built self-consistently from the sources and the sinks. As a
result, we could extract not only profiles of fluid parameters, like density and temperature, but
also detailed energy distribution functions in time, CX and ionization rate profiles.
References
[1] H.W. Müller et al., Nucl. Fusion 51 (2011) 073023
[2] D. Tskhakaya et al., Journ. Nucl. Materials 438 (2013) S522–S525
