EFFECT OF SECONDARY ELECTRON EMISSION ON SUBNANOSECOND BREAKDOWN IN HIGH-VOLTAGE PULSE DISCHARGE

A subnanosecond breakdown in high-voltage pulse discharge is studied in experiment and in kinetic simulations for mid-high pressure in helium. It is shown that the characteristic time of the current growth can be controlled by the secondary electron emission. We test the influence of secondary electron yield on plasma parameters for three types of cathodes made from titanium, silicon carbide and Cu Al Mg-alloy. By changing the pulse voltage amplitude and gas pressure, the area of existence of subnanosecond breakdown is identified.39-3

EFFECT OF SECONDARY ELECTRON EMISSION ON SUBNANOSECOND BREAKDOWN IN HIGH-VOLTAGE PULSE DISCHARGE

39-39A subnanosecond breakdown in high-voltage pulse discharge is studied in experiment and in kinetic simulations for mid-high pressure in helium. It is shown that the characteristic time of the current growth can be controlled by the secondary electron emission. We test the influence of secondary electron yield on plasma parameters for three types of cathodes made from titanium, silicon carbide and Cu Al Mg-alloy. By changing the pulse voltage amplitude and gas pressure, the area of existence of subnanosecond breakdown is identified

Limit characteristics of switches based on planar open discharge

The limit characteristics of switches based on open discharge (OD) with counter-propagating electron beams were studied. Such switches (kivotrons) are able to generate high-voltage pulses with a sub-nanosecond leading edge. Separately obtained limit values of the switch parameters are as follows: current density up to 1000 A cm−2, operating voltage up to 100 kV, switching time down to 100 ps, the degree of pulse compression up to 100, a pulse repetition frequency up to 100 kHz (in burst mode), and an efficiency of more than 0.9. It was shown that the fast current development arises when the discharge self-sustaining mode is caused by the photoemission from the cathodes due to the resonant radiation emitted by fast helium atoms that have a large Doppler shift with respect to the line center. As a result, the emitted radiation reaches the cathodes without absorption by the helium gas. The presence of a fast atom group with an energy determined by the applied voltage was experimentally demonstrated. The dynamics of the plasma decay was studied. It is shown that the radiative, collisional-radiative, and three-body collision recombination mechanisms significantly contribute to the afterglow decay only when the plasma density remains higher than 1012 cm−3. The main mechanism of the further plasma decay is the diffusion of plasma particles onto the wall. Therefore, the effect of recombination in the plasma bulk is observed only during the first 10–20 μs of the afterglow. The results of the lasing characteristics of a copper vapor laser excited by pulses generated by an OD-based switch are presented

Limit characteristics of switches based on planar open discharge

The limit characteristics of switches based on open discharge (OD) with counter-propagating electron beams were studied. Such switches (kivotrons) are able to generate high-voltage pulses with a sub-nanosecond leading edge. Separately obtained limit values of the switch parameters are as follows: current density up to 1000 A cm−2, operating voltage up to 100 kV, switching time down to 100 ps, the degree of pulse compression up to 100, a pulse repetition frequency up to 100 kHz (in burst mode), and an efficiency of more than 0.9. It was shown that the fast current development arises when the discharge self-sustaining mode is caused by the photoemission from the cathodes due to the resonant radiation emitted by fast helium atoms that have a large Doppler shift with respect to the line center. As a result, the emitted radiation reaches the cathodes without absorption by the helium gas. The presence of a fast atom group with an energy determined by the applied voltage was experimentally demonstrated. The dynamics of the plasma decay was studied. It is shown that the radiative, collisional-radiative, and three-body collision recombination mechanisms significantly contribute to the afterglow decay only when the plasma density remains higher than 1012 cm−3. The main mechanism of the further plasma decay is the diffusion of plasma particles onto the wall. Therefore, the effect of recombination in the plasma bulk is observed only during the first 10–20 μs of the afterglow. The results of the lasing characteristics of a copper vapor laser excited by pulses generated by an OD-based switch are presented