Analysis of the trigger characteristics for a pseudospark switch triggered by nanosecond focused laser

Clarifying the trigger characteristics of pseudospark switch triggered by laser (backlight thyratron, BLT) is crucial for optimizing the trigger performance under different conditions. This paper investigates the electron and ion emission characteristics of metal irradiated by nanosecond focused laser, and tests the trigger characteristics of BLT triggered from the back of the cathode (CBLT) and the back of anode (ABLT) with different targets (Mg, Ti, Cu, Mo, W), and discusses the trigger mechanism. The trigger characteristics of CBLT depends on the emission of prompt electrons e 1 and the expansion of ultrafast electrons e 2 . When the laser energy epsilon is less than 0.3 mJ, there will be no e 1 emission, and low -density metals (e.g. Mg and Ti) are prone to ablation, resulting in large e 2 amplitude and short trigger delay t d . Due to the slow speed of e 2 , t d of CBLT has an exponential relationship with the laser irradiation position. When epsilon is increased to above 1 mJ, different metals can be fully heated, and the emission of e 1 will be enhanced and play a major role in trigger. In this case, metals with high melting and boiling points will produce more e 1 , so the trigger performance of Mg is the worst and W is the best. Due to the fast speed of e 1 , the sensitivity of t d of CBLT triggered by e 1 to the laser irradiation position is low, and the trigger lifetime can be improved by fine-tuning the laser irradiation position. The trigger of ABLT depends on the expansion of fast ions i 2 , and heavy metal ions diffuse easily in the background gas, so the laser irradiation area where ABLT can be stably triggered is larger, and the corresponding trigger performance of ABLT is better.