High-β Injection into a Magnetic Mirror Field

Publisher Website
Google Scholar
Abstract
Axial injection of a high‐density helium plasma into a magnetic mirror has been experimentally studied. Observations of the plasma‐field interaction were made with magnetic probes, electrostatic probes, piezoelectric probes, and an optical monochromator which analyzed emission‐line profiles. In the central plane of the mirror a density of 2 ± 1 × 1015 ions/cm3 and a maximum ion temperature of 10 ev are indicated. In the upstream region ion temperatures of 35 ± 5 ev were recorded. Diamagnetic signals show that the high‐β plasma ``stagnates'' near the upstream throat of the mirror. Also, the derived plasma pressure measured on axis decreases exponentially downstream. Piezoelectric‐probe measurements show large axial‐momentum transfer rates in the downstream region of the mirror, where no diamagnetic signals are observed. The data are compared with a fluid model of a plasma which describes the injection, ``stagnation,'' and effusion along field lines. This experiment indicates that the axial injection of a collision‐dominate, high‐β plasma into a static mirror field is not efficient for producing and confining a high‐temperature plasma.