Stimulated Ignition and Quenching of the Cathode Spot in a Low-Power Discharge with Plasma Injection

Experimental results are presented on the current commutation in a low-power gas discharge with external plasma injection. Correlation between current commutation and cathode spot ignition is established. It is shown that the cathode spot is ignited synchronously with the filling of the discharge gap with dense plasma and quenched synchronously with the release (gas-dynamic unloading) of the gap from the plasma. It is found that the spot is ignited over 1-30 ns due to the local explosive heating of the cathode surface (at a heating rate of higher than 10(12) K/s) by the field emission current. It is also shown that the spot is quenched over a time of less than 100 ps and that the processes leading to the quenching develop simultaneously in all cells of the cathode spot.