Speaker
Dr
Alexei Beklemishev
(Budker Institute of Nuclear Physics)
Description
Sections with helical corrugation of the magnetic field are currently considered for supplemental improvement of axial confinement in gas-dynamic mirror traps [1,2]. The $E\times B$ plasma rotation in such a field leads to the effective axial motion of magnetic mirrors. If it is coupled to enhanced plasma scattering (to facilitate ion exchanges between trapped and passing populations) such motion is capable of transferring axial momentum from the magnetic field coils to the plasma flow. Theory also predicts radial pinch effect coupled to this momentum transfer that is capable of contracting or expanding the discharge in radius. The fact is that different components of plasma transport in helically corrugated sections are inherently coupled and should be considered together.
This paper will attempt theoretical description and numerical modeling of the radial and axial transport components in a low-corrugation-helical-mirror section that is attached to a plasma reservoir (main trap cell). Different models of ion scattering (classical and turbulent) are considered. A new method of plasma refueling by means of the radial pinch of cold ions from the plasma periphery is suggested. Design of the ionization zone in the low-field phase of the corrugation as in the helical plasma thruster [3] allows to inject almost all cold ions into the reservoir without significant cold-ion outflow into the expander. This lowers the energy cost of refueling and eliminates the risk of charge-exchange losses associated with schemes of the main-cell refueling. Besides, the effective momentum transfer from the magnetic field to the cold inflow provides a new way of transferring axial momentum to weakly collisional plasmas. Additional plasma scattering caused by such a flow is accounted for.
This work has been supported by Russian Science Foundation (project N 14-50-00080)
[1] A.D. Beklemishev, Fusion Science & Technology 63 (1T), 355 (2013)
[2] V.V. Postupaev et al., Fusion Engineering and Design 106, 29 (2016)
[3] A.D. Beklemishev, Physics of Plasmas 22, 103506 (2015)
Primary author
Dr
Alexei Beklemishev
(Budker Institute of Nuclear Physics)
