ELECTRONIC PROPERTIES OF THE PENNING DISCHARGE PLASMA.
Interim technical rept.,
CORNELL UNIV ITHACA NY SCHOOL OF ELECTRICAL ENGINEERING
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Plasmas produced in a Penning dicharge have been studied theoretically and experimentally for possible use as an active electronic medium in high-frequency amplifiers, oscillators, or noise generators. The work has been particularly directed toward understanding the mechanism of particle transport across the magnetic field, and the associated instabilities. Measurement techniques included microwave scattering, Langmuir probe, and particle energy analysis typical operating conditions were ne 10 to the 10th power - 10 to the 12th powercu cm, Te 2 - 5 eV, discharge current 100 - 500 ma, magnetic field strength 100-500 gauss, and pressure 10 to the minus 4th power - 10 to the minus 2nd power Torr in Ar, N2, and H2. Density profiles, radial diffusion, and electron energy distributions were measured. The last was non-Maxwellian with two distinct peaks. Oscillations of 4-5 Kcs and over one volt peak-to-peak were associated with increased radial diffusion. Their frequency and amplitude depended on the gas, magnetic field, pressure, and discharge current. Nonpropagating ion oscillations, excited by the anisotropic electron velocity distribution were found from 300 Kcs to 500 Kcs only in Ar discharges. The maximum amplitude occurred at the column edge. As the magnetic field increased the frequency increased, and the amplitude decreased. Between the electron cyclotron and electron plasma frequencies noise was detected, with broad peaks at the cyclotron frequency and its harmonics. Theoretical calculations relating the lower frequency oscillations to the measured diffusion rate are presented.
- Plasma Physics and Magnetohydrodynamics
- Radiofrequency Wave Propagation