Controlling Charge and Current Neutralization of an Ion Beam Pulse in a Background Plasma by Application of a Small Solenoidal Magnetic Field

Abstract

Propagation of an intense charged particle beam pulse through a background plasma is a common problem in astrophysics and plasma applications. The plasma can effectively neutralize the charge and current of the beam pulse, and thus provides a convenient medium for beam transport. The application of a small solenoidal magnetic field can drastically change the self-magnetic and self-

Physics of E × B discharges relevant to plasma propulsion and similar technologies

“…Ion azimuthal currents are created too, but (with possible VASIMR's exception) these are paramagnetic and decelerate the plasma beam [367], [375]. This paramagnetic effect is stronger the more magnetized the ions are and has been observed in propagation of an ion beam along a straight magnetic field [376]. Since high ion magnetization is negative in terms of paramagnetic effects and detachment, there must exist an intermediate magnetic field strength optimizing the propulsive features of a MN.…”

Charge and Current Neutralization of an Ion-Beam Pulse Propagating in a Background Plasma along a Solenoidal Magnetic Field

“…pe and c=! pe ' r b , which is observed in numerical simulations and can also be derived analytically [8]. In the presence of the solenoidal magnetic field, the radial force acting on the beam ions can change sign from focusing to defocusing, because the radial electric field increases more rapidly than the magnetic force ÿZ b V bz B , as the solenoidal magnetic field increases.…”

“…This criterion is generalized to the case of relativistic beams in Refs. [8,9]. This threshold value of solenoidal magnetic field is relatively small for nonrelativistic beams.…”

“…We look for stationary solutions in the reference frame of the moving beam, i.e., where all quantities depend on t and z exclusively through the combination V b t ÿ z. Here, for brevity, we consider nonrelativistic beams, although the results can be calculated for relativistic beams as well [8,9]. We further consider cylindrically symmetric, long beam pulses with length l b and radius r b , satisfying l b V b =!…”

“…pe , the beam generates whistler and lower-hybrid waves, and this effect is considered in Refs. [8,9].…”