Investigation of the stability of the electron source with a multi-aperture plasma emitter generating a large cross-section electron beam

M S Vorobyov,V V Shugurov,S A Sulakshin,N N Koval

doi:10.1088/1742-6596/652/1/012048

M S Vorobyov, V V Shugurov + Show 2 more

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https://doi.org/10.1088/1742-6596/652/1/012048

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Abstract

An experiment was performed to investigate the electric strength of the high-voltage acceleration gap of an electron source with a multi-aperture plasma emitter generating a beam of large cross section (750 × 150 mm2) extracted into the atmosphere through a thin metal foil. It has been shown that the use of a mask in the plasma emitter which partitions the overall emission region to produce a plurality of small-cross-section beamlets, so that the extracted beam is a superposition of beamlets formed by individual emission units whose plasma boundary is stabilized by a fine metal grid, increases the electric strength of the high-voltage acceleration gap. This is of critical importance in cases where the electron source is operated in a repetitive pulse mode at high average power of the beam. In addition, an increase in the electric strength of the acceleration gap is promoted by that the modernized cathode assemblies of the plasma emitter are arranged normal to the axis along which electrons are extracted into the acceleration gap.

Highlights

Increasing the electric strength of the acceleration gap in high-voltage electron sources is one of the main problems that must be solved in designing and using systems of this type [1,2,3]
Experimental procedure The experiment was carried out on DUET, a modernized wide-aperture pulsed electron source with a grid plasma cathode (Fig. 1) capable of producing an electron beam with the following key parameters: an electron energy of up to 200 keV, emission current of up to 50 A, pulse duration of up to 100 μs, pulse repetition rate of 50 s-1, and beam dimensions of 750 mm × 150 mm with the current density distribution over the beam cross section uniform to within ± 15% of the average current density. It is well known [9] that the arrangement of the cathode assemblies in a plasma emitter normal to the axis along which electrons are extracted increases the electric strength of the high-voltage acceleration gap. This is probably due to a decrease in the number of the cathode material microdroplets formed as a result of the operation of the cathode spot [8] both on the emission grid and in the region of the acceleration gap
The mechanism of plasma generation in the plasma emitter electrode system is the following: The electrons produced due to the operation of the cathode spot are accelerated in the cathode layer and enter the space of the main discharge hollow anode with an energy roughly corresponding to the discharge voltage

Summary

Introduction

Increasing the electric strength of the acceleration gap in high-voltage electron sources is one of the main problems that must be solved in designing and using systems of this type [1,2,3]. It is well known that the use of plasma emitters where electrons are emitted only from certain sites bounded with an emission grid increases and stabilizes the parameters of the generated beam [4,5,6,7] In systems of this type, called multi-aperture electron sources, large- cross-section beams are generated due to the superposition of individual beamlets, each being generated in the its own acceleration unit consisting of two or more electrodes with coaxial holes.

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