INTERACTION OF A HIGH CURRENT ELECTRICAL DISCHARGE WITH ITS SELF-INDUCED MAGNETIC FIELD IN THE PRESENCE OF GAS FLOW.
Final rept. 30 Jun 64-30 Jun 66,
AVCO MISSILES SPACE AND ELECTRONICS GROUP LOWELL MASS AVCO SPACE SYSTEMS DIV
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An electrical discharge is considered between two electrodes arranged axisymmetrically. Discharge currents are used up to 2500 amperes in a steady state and in the presence of a nitrogen flow rate of the order of a few hundred milligrams per second. The main objective is to determine quantitatively the importance of magnetoplasmadynamic effects in the acceleration of plasma. After a brief consideration of the analytical background, several experiments are discussed and the corresponding results are analyzed. It was determined that the self-magnetic field makes a substantial contribution, as high as 60 percent or higher in certain cases, to the acceleration of plasma. The particularly effective mechanism in these experiments seems to be the self-induced compression in the discharge which is also manifested as a cathode tip overpressure. It was determined that the overpressure in question depends strongly on the discharge current, but is drastically reduced in the presence of an externally applied magnetic field. An interesting by-product of pressure measurements at the cathode tip is the determination of the cathode spot radius which was found in the near vicinity of 5 mm with a small but detectable dependence on both the current and the pressure. Further experiments and experimental results are also presented from measurements of the impact pressure, the plasma velocity, and electric current density in the plasma flow. Author
- Plasma Physics and Magnetohydrodynamics