Enhancement of emission currents in plasma electron sources based on a low-pressure arc discharge

The paper reports on a theoretical and experimental study of the discharge plasma generation with an enhanced electron emission current in a plasma electron source based on a low-pressure arc discharge with a grid-stabilized plasma emission boundary. The source operates at a pressure in the working chamber of p = 0.02-0.05 Pa (Ar), accelerating voltage of up to U_a = 10 kV, and longitudinal magnetic field for electron beam transport of up to B_z = 0.1 T. The experiments show that in the mode of electron emission from the plasma, the voltage U_d between the cathode and grid electrode changes its sign. The numerical simulation demonstrates that the plasma potential and voltage U_d depend on the electric field penetrating from the acceleration gap into the discharge region through the grid meshes, and on the discharge current, gas pressure, geometric transparency of the grid, and gas kind. It is shown that the main mechanisms responsible for the increase in the discharge current and electron emission current from the plasma are associated with secondary ion-electron emission from the emission electrode and with positive feedback between the region of cathode plasma generation and the channel of electron beam transport.