Effects of Optical Pulse Parameters on a Pulsed UV-Illuminated Switch and Their Adjusting Methods

Abstract

Ultraviolet (UV) illumination can effectively shorten the statistical lag and jitter in gas breakdown processes. The spark gap discharge can produce abundant spectrum including UV waveband. In this paper, a simple but reliable spark gap operating with N 2 at atmospheric pressure is used to test optical radiation characteristics, such as spectrum intensity, rise time, fall time, and duration of optical pulse, which are adjusted by changing the circuit or configuration parameters. Three UV-illuminated switches with different UV spark gap configurations have been tested. The experimental results approve our assumption. With a uniform electric field UV spark gap, the breakdown voltage standard deviation percentage of the switch is 0.74%.Index Terms-Breakdown characteristics, jitter, optical pulse parameter, pulsed power technology, pulsed switch, ultraviolet (UV) illumination.

Optimization of a Nanosecond Pre-Ionization Switch’s Breakdown Jitter Characteristic Based on a Probability Distribution Model of Electron Avalanche’s Initiation

“…It is important to note how the pre-ionization works [5], [15]. From Figure 1(c) we can see that the main gap electric field is designed to be shielded at the trigger gap, and it is impossible that the electrons in the arc channel of the trigger gap lead to an electron avalanche and breakdown of the main gap.…”

“…From Figure 1(c) we can see that the main gap electric field is designed to be shielded at the trigger gap, and it is impossible that the electrons in the arc channel of the trigger gap lead to an electron avalanche and breakdown of the main gap. Considering that the first ionization energy of nitrogen molecule is about 15.5eV, and the photon's energy is in the range of 3.1eV to 3.9eV [15], so it is also impossible that photons generated by spark discharge will ionize the nitrogen molecules and initiate an electron avalanche near the trigger gap. The work function of stainless steel is about 4.4eV, but the photons are generated when the electric field strength at the cathode surface is high enough, the actual work function will be smaller than 4.4eV.…”

“…Effective UV illumination started to appear when the trigger gap broke down. Initial electrons in the main gap generated by cathode photoemission mainly appeared when UV illumination appeared, and UV illumination only sustained for a short period, not during the whole spark discharge process [15], so the initial electrons could only appear during a specific time. It should be specially noted that the electrons in the arc channel of the trigger gap could not drift towards the main gap anode (and become initial electrons) because the trigger plane shielded the main gap electric field at the trigger gap.…”

“…To explain why pre-ionization under low gas pressure was ineffective, the ability of initial electrons with different generating times and numbers to initiate an electron avalanche should be analyzed. The probability model [18] and diagnosis results [15] are used for reference in this section to analyze the influence of generating time and rate of initial electrons on the pre-ionization effect.…”

“…Diagnosis results indicate that the rise time of UV optical pulse was smaller than 5ns when the trigger gap had a slightly non-uniform field, and FWHM of UV optical pulse was smaller than 15ns when there was no energy storage capacitor (Cs) in parallel with the gap [15]. The typical waveform of the UV optical pulse (central wavelength 337 nm) is shown in Figure 10 [15].…”