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

Abstract

The breakdown jitter characteristic of a self-triggered pre-ionization switch that works under pulses with the rising time of about one hundred nanoseconds was improved based on the probability distribution model of electron avalanche's initiation. Contrary to what we might imagine, premature pre-ionization nearly brought about no improvement on the breakdown jitter characteristic. To reduce the switch jitter, analysis of the probability distribution model indicated that the generating rate of initial electrons should maintain a high value when the electric field in the gap was high enough to initiate an effective electron avalanche. Experimental results proved that adjusting the breakdown time of the trigger gap or letting the electrons in the arc channel of the trigger gap become a steady source of initial electrons could both reduce the breakdown time delay jitter to 1ns-2ns when the breakdown time was about 95% of the peak time, this means that high energy transfer efficiency and low jitter were realized simultaneously.INDEX TERMS Gas switch, nanosecond pulse, pre-ionization, self-triggering, time delay jitter.

A low-jitter self-triggered spark-discharge pre-ionization switch: primary research on its breakdown characteristics and working mechanisms

“…In the UV-illumination switch, due to the shielding effect of the trigger plane, the main gap electric field strength at the trigger gap is only ∼50 kV cm −1 (average electric field is ∼166.7 kV cm −1 ). It is hardly possible for the electrons in the spark channel of the trigger gap to drift towards the main gap anodes during the time duration of input pulses (∼200 ns) [17].…”

“…Because initial electrons are supposed to be generated through photoemission [12] with low efficiency of no more than 1/100 [16], and FWHM of the UV-illumination generated by trigger gap discharge is generally less than 15 ns [12], the triggering time, which is determined by the voltage division ratio between the main gap and trigger gap, must be adjusted carefully. Figure 1(b) indicates that the effectiveness of UV-illumination varies dramatically as the ratio changes [17,18]. The time jitter increases as the ratio decreases (earlier triggering time), and the switch might fail to break down at the front edge, which seriously threatens the insulation.…”

A calculation model for breakdown time delay and jitter of gas switches under hundred-nanosecond pulses and its application in a self-triggered pre-ionized switch

“…When the rise time of input pulses is several hundred nanoseconds, statistical time delay t s accounts for a large portion of breakdown time delay t d [10,19,30]. T s is the time that the first initial effective electron appears, which is related to both the number of initial electrons and the electric field strength [17,23]. To obtain the distribution function of T s , the switch gap needs to be divided into regions of size n. For the convenience of analysis, we first assuming t jtr =0 and the conditional cumulative distribution function of T s at the jth region (F j ) can be derived.…”

“…in expression (23), N e is the electron density, α s is the photoemission coefficient, v e is the drift velocity of electrons, subscript 1 means the parameters are calculated in volume V 1 [33].…”

“…The statistical time delay (t s ) is related to the spatial and temporal distribution of initial electrons and time-varying electric field [13][14][15][16][17]23]. Field emission is unlikely to be a source of initial electrons when the electrodes are mechanically polished and the working electric field is 30-140 kV cm −1 [13,14,[24][25][26][27].…”