Speaker
Dr
Ivan Chernoshtanov
(Budker Institute of Nuclear Physics)
Description
Azimuthal current generation in a mirror trap via powerful off-axis neutral beam injection [1] is method of field-reversal configuration (FRC) formation. Theoretical consideration [2] shows that method faces with numerous difficulties, for example, MHD instabilities of high pressure plasma and fast ions current cancellation by electron current at field null. Experimental investigation of field reversal in 2XIIB machine [1] has shown that increasing of fast ions pressure is limited by anomalous ions scattering caused by excitation of kinetic instability (probably the drift-cyclotron loss-cone instability).
Facility for experimental studying of field reversal in mirror machine is being designed in the Budker INP SB RAS now [3]. 3D hybrid Particle-in-Cell code was developed for studying processes which can prevent field reversal. The injection geometry (including ballistic beams focusing) and fast atoms trapping because of charge exchanging and ionization are taken into account. 3D PiC method taking into account the ion-ion collisions, charge-exchanging and electron drag is used for calculation of the charges and currents generated by fast ions. Electrons evolution, electron charges and currents are calculated from the two-fluid MHD equations taking into account finite electron viscosity and conductivity. Evolution of target ions can be calculated by the PiC method or by solving of the two-fluid MHD equations. Thus various processes can be studied, such as MHD and kinetic instabilities, electron current self-generation, target plasma penetration through closed field lines.
The preliminary results of simulations of field reversal under the parameters of planned experiment are presented. In axisymmetric case (dependence of fields on the azimuthal coordinate is neglected) the field reversal is achieved if electron temperature is high enough (of the order 100 eV). Fast ions losses caused by the electron drag are unacceptably high when temperature is too lower. The small-scale convection which prevents the electron current self-generation is observed. Probably the convection is driven by Kelvin-Helmholtz instability caused by potential drop between areas with closed and opened field lines [4]. Anomalous fast ions scattering caused by kinetic instabilities is observed in fully 3D simulations. Ways of the MHD and kinetic instabilities stabilizing are discussed.
This work was supported by Russian Science Foundation (Project No. 14-50-00080).
References:
[1] W.C.Turner, et. al., Nucl. Fusion, Vol.19, No 8, p.1011-1028 (1979)
[2] L.D. Pearlstein, et.al., Plasma Phys. Controlled Nuclear Fusion Res. (Proc. 7th Int. Conf. Innsbruck, 1978). Vol. 2, 457-466 (1979)
[3] P.A. Bagryansky, et. al. This conference.
[4] A.F.Liffschitz, R.Farengo, N.R.Arista, Nuclear Fusion, V.42, No 7, 863-875 (2002)
Primary author
Dr
Yuri Tsidulko
(Budker Institute of Nuclear Physics)
Co-author
Dr
Ivan Chernoshtanov
(Budker Institute of Nuclear Physics)
