Plasma Production by Neutral-Atom Injection: Equations and Numerical Solutions

Abstract

Differential equations and their solutions for the formation of a high-energy plasma by the injection and trapping of energetic atoms in a magnetic-mirror geometry are discussed. The present approach differs from previous treatments in that the finite orbit size of the ions and the spatial dependence of the trapping process are included in the equations. By including the spatial dependence it was possible to evaluate the effect of charge exchange of trapped ions with neutral-beam atoms. Although not affecting the total number of trapped ions, this process results effectively in a change of the mean radial position of the ions. The effect on plasma growth rates of charge exchange of the trapped ions with beam atoms was found to be essentially negligible. The solutions for ion density vs time exhibit growth rates similar to those obtained when the plasma density is assumed to be spatially constant. Background gas variations during plasma buildup have also been investigated. Under the present set of conditions the effect of ``gas burnout'' and plasma pumping are small, even at high densities.

Vapor Phase Homo- and Heteroepitaxies of ZnSe Films

“…In equations (1) and (2), we have neglected charge exchange of energetic trapped ions with neutral beam atoms. This process does not affect the total number of trapped ions and the resulting spatial redistribution of the hot ions does not significantly change the plasma growth rate (FUTCH et al, 1962). The contribution of inverted cascading (HISKES, 1963;KARPUSHKINA and GRECHUKIN, 1964) to the Lorentz-force trapping has been neglected here in the interest of simplification.…”

“…THE differential equations and their solutions for the formation of high energy plasma by the injection and trapping of energetic atoms in a magnetic-mirror geometry are well known (GIBSON et al, 1959;POST and DAMM, 1960;FUTCH et al, 1962;SWEETMAN, 1962). In a magnetic-mirror field, the cold ions (produced by chargeexchange collisions and by ionization of the background gas) may be neglected since they are rapidly scattered into the mirror escape cone and lost from the system.…”

High beta capture and mirror confinement of laser produced plasmas. Semiannual report, February 1, 1976--June 30, 1976

“…In Ref. 20 it was found that if the neutral beam is directed at the proper ~alf of the target plasma, the .Plasma losses by migration of guiding centers will be negligibly small. The study of these effects in LITE has been reserved for an analysis of the type described in Ref.…”

“…The remainder contributes to growth of the plasma volume or sustains it against charge exchange erosion. Now, since (20) (Ref.…”

High beta capture and mirror confinement of laser produced plasmas. Semiannual report, February 1, 1975--June 30, 1975

“…In the first case N(t) = N 0 (t) the density of cold neutrals next to the plasma, while in the second N(t) = Ny(t) the cold neutral density between the magnet and the vacu.um chamber wall. 20 it was found that if the neutral beam is directed at the proper ~alf of the target plasma, the .Plasma losses by migration of guiding centers will be negligibly small. The study of these effects in LITE has been reserved for an analysis of the type described in Ref.…”