Stabilization of a Neutral-Beam—Sustained, Mirror-Confined Plasma

Abstract

We report results of plasma confinement experiments with an auxiliary warm-plasma component flowing along magnetic field lines to suppress ion-cyclotron instabilities. The reduced plasma losses, with the lower fluctuation amplitude, permits neutral-beam buildup of a 13-keV deuterium plasma to densities as high as 4 x 10 13 cm" 3 corresponding to peak beta values of 0.4. Variation of the beam energy demonstrates that longer confinement times are achieved at higher ion energies.

Magnetic fusion energy annual report, July 1975--September 1976

“…The resulting hot-ion density was estimated to be "1 X I0' ! ions/cm -' for a 22-A neutral beam and a target density of 1.4 X 10" particles/cm 3 . The plasma pulses from the titanium washer gun were 1 through 6 ms long.…”

“…Of greatest im portance, peak plasma beta reached 1.6 and peak density equalled 1.5 X 10 ! * particles/cm 3 • Scaling laws demonstrating increase of energy confinement and plasma beta with injected neutralbeam current.…”

“…From the end-loss measurement, we estimated the central density of isotropic warm plasma to be 3 through 10 X 10" particles/cm 3 A picture emerged from our measurements: the streaming-plasma gun generated a stagnant reser voir of plasma outside the mirror with a density of 10 w particles/cm J and an electron temperature of ~40 eV. Ions and electrons were contained for several transit times between gun and mirror, Stream density was attenuated in the mirror throat, allowing an electron temperature in the confine ment region between mirrors to exceed that in the external plasma.…”

“…The mechanical effects of He in metals were studied using a tritium decay technique to inject 3 He into Nb and Nb-1% Zr specimens. Also, a computer model was studied which simulates high-energy collision cascades in a crystal lattice.…”

Two-Stage-Discharge Ion Source

“…This, however, postulates the availability of a source plasma possessing the properties o f : (1) a n ion density in the region of ion beam formation intense enough to form a high current ion beam; (2) a spatially uniform density distribution over the wide area of multiapertures ; (3) provision of a sufficient quality of hot electrons ; (4) a mechanism of ion transport in the discharge chamber such that ions produced a t a considerable distance from the ion extraction apertures also are duly transmitted to the region of ion beam formation(6).…”