Investigation of the characteristics and mechanism of subnanosecond switching of a new type of plasmas switches. II switching devices based on a combination of 'open' and capillary discharges-eptrons

The results of investigation of a new type of switch (eptron), which expands the opportunities of voltage waveform tailoring for low temperature plasma applications, are presented. This switch consists of the device with counter-propagating electron beams (kivotron), which acts as a plasma cathode, and capillary integrated with the kivotron into a single device. The main advantage of a discharge in a capillary is various mechanisms of charge neutralization at different plasma densities. At a low density (10(10)-10(11)) cm(-3), free transport of electrons to the walls of the capillary occurs, due to which a large delay in the development of the discharge is realized. At a high plasma density, due to Debye screening, a rapid charges multiplication occurs and fast switching is realized. Under optimal conditions corresponding to the maximum value of the Townsend multiplication coefficient, a switching time less than similar to 1 ns is achieved. The comparative characteristics of the kivotron and eptron due to different mechanisms of subnanosecond switching are considered. The kivotron has a much lower inductance, which allows it to receive currents of tens of kiloamperes. Eptron operates more efficiently with a small characteristic size of the capillary, preferably a few tens of millimetres square. As a result, plasma recombination in the capillary in the eptron in the interpulse interval is much faster than in the kivotron, which allows operating at pulse repetition frequency above 100 kHz and the operating voltage of tens of kilovolts. The subnanosecond switching time in the eptron is realized at currents up to similar to 1 kA. Nevertheless, eptron provides new opportunities of voltage waveform tailoring, specifically for pulses generating with a subnanosecond leading edge. Particularly, it is demonstrated that lasing characteristics of BaII and HgII lasers on self-terminating transitions are significantly improved in comparison with conventional power supply.