Diagnostic Measurements on a Highly Ionized, Steady-State Plasma

Abstract

Techniques and results are given for various measurements made on a highly ionized helium plasma in a steady-state plasma system (which employs a longitudinal magnetic field of approximately 1 kilogauss). Neutral-particle pressures ranged from about 3 × 10−4 mm Hg near the source to about 10−5 mm Hg in the downstream region. Spectroscopic measurements showed principal impurities were C, N, and O ions (up to C3+, N4+, and O4+ states). Doppler broadening measurements of He+ λ4686 revealed ion temperatures up to 10 eV. Probe measurements indicated electron temperatures up to 20 eV and maximum ion densities of a little over 1013 cm−3. Microwave transmission measurements (at λ = 4 mm and 8 mm) gave supporting evidence that the electron density exceeds 1013 cm.