Enhancement of emission currents in plasma electron sourcesbased 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 р = 0.02–0.05 Pa (Ar), accelerating voltage of up to Ua = 10 kV, and longitudinal magnetic field for electron beam transport of up to Bz = 0.1 T. The experiments show that in the mode of electron emission from the plasma, the voltage Ud between the cathode and grid electrode changes its sign. The numerical simulation demonstrates that the plasma potential and voltage Ud 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

Modernization of cathode assemblies of electron sources based on low pressure arc discharge

The paper presents modified cathode assemblies, including their main characteristics, for plasma electron sources based on a constricted low-pressure arc initiated by a discharge in crossed electric and magnetic fields. One of the modified cathode assemblies allows the electrode system of the auxiliary discharge to operate at a pressure of≈0.3 Pa, as against ≈ 10 Pa before the modification, provides a larger diameter constriction of the pulsed (up to [tau]=250 [mu]s) arc, and thus extends the range of operating currents for the plasma-cathode discharge system up to I[d]=300 A. The other modified assembly operates at widely varying discharge currents I[d]=5-100 A, provides lesser amounts of cathode microdroplets at the discharge electrodes, and allows the arc to operate at comparatively low voltages. The use of cathode assemblies adapted for specific discharge systems extends the capabilities of plasma- emitter electron sources as well as the range of their applications in scientific and technological fields