Speaker
Dr
Dmitriy Skovorodin
(BINP)
Description
Axially symmetric magnetic mirrors could be attractive as neutron source and alternative fusion reactor [1,2]. Plasma losses from mirrors are dominated by longitudinal outflow. Ions are confined between mirrors in central region of trap. Commonly plasma in a trap has positive electrostatic potential that holds the electron loss equal to the ion loss. The secondary emission of electrons from end plate along with ionization of neutral gas in expander region can strongly affect the confinement. The potential barrier height will be reduced if secondary electrons can penetrate the inner region of trap. Those electrons could overcome the mirror due to acceleration by electric field. It depends strongly on distribution of electrostatic potential along the lines of magnetic field. Scattering of electrons results in trapping of a part of them between the magnetic mirror and Debye sheath at the wall. Presence of the trapped population moves a part of potential drop from the sheath to expander area. Thus, expansion of the magnetic field behind a mirror can reduce electrons recycling from the wall [3,4]. In present work numerical kinetic model is developed to study the influence of electron scattering on the distribution of electric potential in expander. The model solves collisional kinetic equation for electrons. It is supposed that ions flow through the expander is collisionless. The electric potential is determined from the quasi-neutrality condition.
[1] A.D. Beklemishev, Fus. Sci. and Tech., 63 (1T), 46 (2013).
[2] A.A. Ivanov, V.V. Prikhodko, Plasma Phys. Control. Fusion, 55, 1 (2013).
[3] I.K. Konkashbaev, I.S. Landman, F.R. Ulinich, JETP, 47, 501 (1978)
[4] D. D. Ryutov, Fusion Science and Technology, 47, 148 (2005).
Primary author
Dr
Dmitriy Skovorodin
(BINP)
Co-author
Dr
Alexei Beklemishev
(Budker Institute of Nuclear Physics)
