Measurement of Corona Discharge Behavior At Low Pressure and Vacuum

The significance of the reduced electrical strength of low-pressure air gaps near the Paschen's minimum is considered in relation to the proper operation of electrical systems in high altitude and space vehicles. Experiments are described which illustrate the occurrence and magnitude of partial discharges (corona) in air
gaps between insulator and metal surfaces at low pressure and vacuum. The magnitude of the corona pulses observed with alternating voltages varied with pressure, being relatively small at atmospheric pressures and at pressures of about 10-1 torr where glow discharges occurred; the corona pulses were considerably larger for intermediate pressures and for pressures less than 10-1 torr. Although the pulse magnitude is low in the glow discharge region, considerable integrated charge may be transferred in this pressure region. Calculation of the pulse charge magnitudes indicated that the surface area discharged per pulse at low pressure is at least 1/3 to 1/2 of the total available area. The characteristics of corona discharges arising from direct voltages applied to low-pressure gaps are also considered.