A small plasma focus (3.3 kJ) is designed from the viewpoint of simplicity, reliability, and cost effectiveness to act as a source of pulsed high-density plasmas. The simplicity of the device and associated diagnostics coupled with its rich variety of plasma phenomena makes this device ideal for the teaching of plasma nuclear fusion particularly for developing countries where such facilities are at present rarely available. Six sets of the device have been constructed and tested in various gases with better than 95% reliability and reproducibility in various plasma phenomena including neutron production of 0.5–1.0×108 per discharge when operated in 3-Torr deuterium. The design principles, procedures, and parameters are discussed and test results shown.

Published literature shows that the neutron yield of the plasma focus has been modeled in two papers using a thermonuclear mechanism. However, it is more widely held that plasma focus neutrons are produced mainly by nonthermalized mechanisms such as beam-target. Moreover these papers use several parameters which are adjusted for each machine until the computed neutron yield Y n data agree with measured Y n data. For this paper numerical experiments are carried out, using the Lee model code, incorporating a beam-target mechanism to compute the Y n versus pressure data of plasma focus devices PF-400 J and FN-II. The Lee model code is first configured for each of these two machines by fitting the computed current waveform against a measured current waveform. Thereafter all results are computed without adjusting any parameters. Computed results of Y n versus pressure for each device are compared with the measured Y n versus pressure data. The comparison shows degrees of agreement between the laboratory measurements and the computed results.

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Nonrepeatability in measured values of the static breakdown voltage Vs of uniform-field high-pressure gas-discharge gaps necessitates a large number of measurements to be made in order to construct meaningful V, distribution curves. An apparatus has been constructed which is capable of automatic measurement and recording of breakdown voltage data. This enables results to be obtained under more precise conditions than are possible using normal experimental techniques. The design and performance of this system are discussed with reference to some results obtained for pressurized nitrogen. Publ. 90 p 326 Chalmers I D and Thom J 1972 Proc. 2nd Znt. ConJ on Gas Discharges, London 1972: ZEE Conf. Pub[. 90 p 276 Figure 5 (pd = 1500 Torr cm)

The temporal and spatial characteristics of the x-ray emission in a 3 kJ plasma focus are investigated when operating in H, with an Ar admixture. The experiments are performed in a UNU/ICTP PFF device. The x-ray emission is detected with a multichannel system of PIN-Si diodes with different filtering looking axially and radially into the focusing region. Two main periods are observed in the x-ray emission, corresponding to two successive compressions in the focus. X-ray emission arising from electron beam activity and dense plasmas is identified. On the basis of the x-ray emission characteristics several features of the plasma focus dynamics are discussed.