An electron source with a multiaperture plasma emitter and beam extraction into the atmosphere

Abstract

The results of investigating the emission properties of a multiaperture plasma emitter with grid stabilization of the emission-plasma boundary in an electron source with ejection of a generated electron beam from the accelerating gap into the atmosphere through a thin foil. A stainless-steel foil mask with 344 circular holes is laid on an emission grid with dimensions of 750 × 150 mm. The holes form a discrete emission structure of the plasma emitter, from which electrons are emitted under the action of an accelerating voltage. The alignment of the holes in the mask of the emission structure and in the bearing grid of the output foil window, which has the same number of holes with a larger diameter, and the attainment of a coaxial plane–parallel geometry of the accelerating gap allows minimization of the beam loss in the bearing grid of the output foil window. An electron beam is a superposition of elementary beams that are formed by individual emission structures, whose plasma boundaries are stabilized with a fine-structure metal grid. The coefficient of the current extraction into the atmosphere reached 75% of the emission current. In experiments at an accelerating voltage of 200 kV, an emission current of 16 A, and a pulse duration (FWHM) of 40 μs, a beam with an average power of ∼4 kW was ejected into the atmosphere. This value is more than 60% of the beam power in the accelerating gap at a geometrical transparency of the bearing grid of the output foil window of 56%. A further increase in the power was limited by the power of the high-voltage power-supply unit.