WIDE-APERTURE ELECTRON SOURCE WITH A PLASMA GRID EMITTER

摘要

This paper presents a theoretical and experimental investigation of the formation and transport of a large cross-section beam in a low-pressure gas, the discharge plasma characteristics in an electron source with a plasma emitter and beam extraction into the atmosphere through a thin foil. In such a source, the electron beam is a superposition of elementary beams formed by separate emission structures, the plasma boundary of which is stabilized by a fine metal grid. In experiments at an accelerating voltage of 200 kV, emission current of 16 A, and pulse duration of 40 μs, about 4 kW of the beam average power is extracted from the accelerating gap into the atmosphere at the geometric transparency of a supporting grid of the exit foil window equal to 56%. Numerical investigation of the discharge plasma generation, formation and transport of an electron beam also is carried out. It is shown that the characteristics of the discharge plasma depend on the resistance in the hollow anode circuit of the discharge system and on the mask surface area. The main beam current losses are associated with the expansion of the elementary electron beams cross section in the accelerating gap, plasma flowing-in behind the mask, ion current, and losses on the foil.