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Experimental study of pseudospark‐produced electron beams
Abstract
A brief review on the status of pseudospark research is given. A modular pseudospark chamber was built to investigate this new discharge type as a source of intense electron beams. Typical experimental parameters are a brakedown voltage of 25 kV and a discharge current of about 500 A, with an electron beam of ∼100 A and ∼10 ns FWHM emitted through the anode hole into a drift chamber. Electrical parameters of the circuit, including the plasma channel, were evaluated by monitoring the discharge current waveform. First results of emittance measurements of the electron beam are presented. Based on the measured rms emittance of ∼55 mm‐mrad, a normalized brightness of about 2×1011 A/m2‐rad2 is estimated. This characterizes the pseudospark as a high brightness
electron beam
source.
Laser-controlled beamfront accelerator experiments achieved gradients of up to 40 MV/m and proton acceleration to 18 MeV over 40 cm with a beam energy of 900 keV. Beamfront electric field degradiation requirements beam energy to be increased as the gradient is increased. An experiment with a beam energy of 1.5 MeV achieved a 60 MV/m gradient in a 100 cm distance, matching theoretical models. Experiments with psuedospark discharges achieved electron beams of 25 KV, 1000 A/sq. cm., 10 ns with 10(11) A/(m-rad)sq brightness. Theory indicates densities greater than 10(3) A/sq. cm. and brightness greater than 10(11) A/(m- rad)sq are achievable. (jhd)
Strong electron emission from a plasma or a solid surface is the basis of many applications such as high-power switching or intense electron beam generation. The electron emission in pseudospark geometries, from the interior of a hollow cathode and from the outer cathode surface, is discussed. These types of emission are compared with other emission methods by taking into account the electron current density, the spatial and the energy distribution, the beam quality, and the mechanisms, which allow each process to be controlled. A combination of different types of emitters may be the best solution for efficient power switching and for intense electron beam production. As examples, ferroelectric emitters in pseudospark-like switches and in electron beam sources are described.
The authors report experimental results on the production of radiation from ≈20 GHz to ≈100 GHz in a pseudospark-type device. Pulsed emission of radiation occurs from a low (neutral) pressure (≈100 mtorr Ar) discharge, during the initial transient phase, as the plasma is being formed and a pulsed electron beam is temporarily present. A high-energy electron beam (15~20 keV) has been observed along with a high-density plasma in this pseudospark-type device. A beam-plasma interaction is proposed as the mechanism for the radiation generation
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