Characteristics of DC Microdischarge Under Low Pressure

Abstract

DC microdischarge sometimes occurs in aeronautic or space equipment, which put serious threat to the safety of the devices because it has no zero current point. Aeronautic and space equipment is subjected to low pressure or even vacuum. Therefore, it is of great significance to investigate the characteristics of DC microdischarge under low pressure. A test platform of DC microdischarge was built. The DC microdischarge generation setup was put in a vacuum chamber, and the pressure varied from 0.6 kPa to 96 kPa. The current and electromagnetic radiation signals when DC microdischarge occurred were measured by Hall current sensor and Hilbert curve fractal antenna, respectively. The influences of materials, shape and moving velocity of electrode, and pressure were investigated. FFT was applied to analyze the characteristic frequency of the electromagnetic radiation signals. And the characteristic parameters were extracted. When microdischarge generates, the current has high frequency pulses superimposed on the DC current. The fast change of current results in the electromagnetic radiation. The experimental results indicate that the amplitude of the electromagnetic radiation generated by microdischarge varies with the influential parameters. With the decrease of pressure, the amplitude of electromagnetic radiation pulse of DC microdischarge generated by brass, copper and aluminum shows a descending trend, while the change of stainless steel is not obvious. However, the electromagnetic radiation pulse of DC microdischarge has a characteristic frequency range (36–41 MHz), and is independent from pressure, electrode materials, shape and moving velocity.