As a first step in the design of a repetitive pulsed neutron generator, a very small plasma-focus device has been designed and constructed. The system operates at low energy (160 nF capacitor bank, 65 nH, 20–40 kV, and ∼32–128 J). The design of the electrode was assisted by a computer model of Mather plasma focus. A single-frame image converter camera (5 ns exposure) was used to obtain plasma images in the visible range. The umbrellalike current sheath running over the end of the coaxial electrodes and the pinch after the radial collapse can be clearly observed in the photographs. The observations are similar to the results obtained with devices operating at energies several orders of magnitude higher. The calculations indicate that yields of 104–105 neutrons per shot are expected with discharges in deuterium.

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The basic engineering criteria for conceptual design of plasma focus devices is derived from a thermonuclear model, and applied successfully to the operation of small neutron pulsors. The theory is able to explain the variation of the neutron yield with the gas pressure in deuterium-filled chambers, the current evolution, and the electrode geometrical parameters. The performance of a prototype designed to optimize the flux/fluence ratio is presented, contrasting the experimental outcomes with the model. A set of effective design parameters is deduced, which ensure a band confidence of 20%.

The characterization of plasma bursts produced after the pinch phase in a plasma focus of hundreds of joules, using pulsed optical refractive techniques, is presented. A pulsed Nd-YAG laser at 532 nm and 8 ns FWHM pulse duration was used to obtain Schlieren images at different times of the plasma dynamics. The energy, interaction time with a target, and power flux of the plasma burst were assessed, providing useful information for the application of plasma focus devices for studying the effects of fusion-relevant pulses on material targets. In particular, it was found that damage factors on targets of the order of 104 (W/cm2)s1/2 can be obtained with a small plasma focus operating at hundred joules.

An experimental study on hard x-ray production in a small plasma focus device operating in a few hundreds of Joule range is presented. A threshold in the voltage drop on the pinch was observed for x-ray emission. A comparison with Dreicer theory for electrons runaway in plasmas yields significant agreement. The study was performed at a constant pressure (1.8 mbar) of deuterium with three different anode lengths.