Abstract
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 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.
Highlights
Plasma electron sources with a grid-stabilized plasma emission boundary provide stable generation of emission plasma and electron beams with a high current density of jb = 1–10 А/cm2 [1,2,3,4]
The paper studies the effect of a positive feedback between the discharge region and plasma anode on the generation of plasma and electron beam, discharge current, and electron beam current
Of significance in the electron source is the interrelation between the processes occurring in the plasma anode, which is formed in the beam drift space during ionization of the working gas, and the processes developing in the plasma cathode due to secondary ion-electron emission from the surface of grid electrode 3 [7,8,9]
Summary
Plasma electron sources with a grid-stabilized plasma emission boundary provide stable generation of emission plasma and electron beams with a high current density of jb = 1–10 А/cm2 [1,2,3,4]. The processes occurring in the region of the emission grid electrode should be taken into account in designing of both plasma emitters and their power supplies Understanding these processes will allow one to define more accurately the requirements on the parameters of power supplies and to determine the methods that enhance the operation stability of plasma cathodes with a grid-stabilized plasma emission boundary and increase their limiting parameters.
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