Investigation of breakdown voltage and electrical breakdown time delay in air-filled tube in presence of combined gas and vacuum breakdown mechanism

Abstract

This paper presents the experimental data of breakdown voltage and electrical breakdown time delay for air-filled tube at p = 0.7 mbar pressure. The breakdown voltage was measured for product p·d (d is inter-electrode gap) from 0.005 to 0.2 mbar cm, i.e. when breakdown was a consequence of gas and vacuum mechanisms combined. It was shown that the static breakdown voltage, which was determined from experimental data of the dynamic breakdown voltage, retains approximately constant value. The shape of the memory curve, which displays the mean value of electrical breakdown time delay t¯d vs. relaxation time τ, is very similar to that previously obtained in the case of breakdown induced by Townsend's mechanism alone. UV and gamma radiation lead to the decrease of t¯d values for values τ > 30 ms and this decrease is larger in the presence of UV radiation. UV and gamma radiation shorten the relaxation time needed for memory curve to reach saturation. On the basis of exponential and Gaussian distributions of experimental data, the contribution of the statistical time delay and the formative time to total electrical breakdown time delay for different values of relaxation time is considered.