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  • Minimizing Late Currents in...
    Grover, Harpreet Singh; Dawson, Francis

    IEEE transactions on plasma science, 2021-Sept., 2021-9-00, Letnik: 49, Številka: 9
    Journal Article

    One of the key challenges in the design of gas lasers powered by pulsed power circuits pertains to reducing the flow of current through the electrodes during the filamentary discharge phase. This phase occurs after the lasing period ("volume glow") is terminated due to discharge instabilities and the current flow during this period is referred to as late currents. Late currents contribute to electrode erosion. The ejected electrode material contaminates the gas, and lowering the service life of the laser. Snubber circuits are an economic solution to reducing late currents in pulsed power circuits that do not employ a magnetic switch. In a simple snubber, which is connected directly across the main storage/drive capacitor <inline-formula> <tex-math notation="LaTeX">C_{0} </tex-math></inline-formula>, it was found that the stray series inductances of both <inline-formula> <tex-math notation="LaTeX">C_{0} </tex-math></inline-formula> and the high voltage snubber diodes significantly reduced the magnitude of current flowing through the snubber. A new coaxial capacitor and snubber assembly was proposed to improve the effectiveness of the snubber in reducing the late currents. The design exploited the high degree of mutual coupling between the concentric coaxial cylinders to reduce the total inductance in the snubber loop. Experimental results showed an almost 40% reduction in the total charge that flows through the discharge in the late currents stage. Although the improvement was significant, it is expected that improvements to the construction quality of the prototype could potentially lower the late currents even further.