Multi-resolution analysis of partial discharge current in low pressure flash lamps

Flash lamps, in general, are used as intense source of broadband light in applications ranging from medicine, industry and physical sciences. One of its important uses is in optical pumping of amplifiers in solid-state lasers. Flash lamps work on the principle of arc discharge through an inert gas such as xenon or krypton. Main discharge through a flash lamp is preceded by partial discharge caused by a high voltage trigger pulse. Trigger discharge is confined to very low volume along the tube, in contrast to the high energy main discharge which completely fills the inter-electrode space. The amplitude and the frequency contents of the main and partial discharge currents depend on the pulse forming network^{1, 2}. These parameters exhibit certain degree of variation and randomness associated with environmental conditions. Hence, characterizations and performance monitoring of the flash lamps are important requirements in large-scale systems such as high power laser chains for laser plasma interaction studies. This paper describes an experimental technique to understand effects of ground plane on partial discharge current in flash lamp operation. Signal processing of the discharge current was done using multi resolution analysis, which decomposes the transient time domain current signal into low frequency and high frequency components. When the resolved components were compared, it was observed that the high frequency components are significantly attenuated in presence of ground plane compared to that in absence of the ground plane. The attenuation of the high frequency components is correlated with more reliable firing of the flash lamps. This shows that we should go for providing a ground plane, which is presently not the case, to improve performance of the flash lamps. It is also suggested that this technique should be used periodically in multistage high power lasers for analysis of flash lamp current to check the flash lamp firing characteristics to exte- d the life and reliability of the flash lamps.