The Lee model couples the electrical circuit with plasma focus dynamics, thermodynamics, and radiation. It is used to design and simulate experiments. A beam-target mechanism is incorporated, resulting in realistic neutron yield scaling with pinch current and increasing its versatility for investigating all Mather-type machines. Recent runs indicate a previously unsuspected “pinch current limitation” effect. The pinch current does not increase beyond a certain value however low the static inductance is reduced to. The results indicate that decreasing the present static inductance of the PF1000 machine will neither increase the pinch current nor the neutron yield, contrary to expectations.

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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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Contrary to the general expectation that performance of a plasma focus would progressively improve with progressive reduction of its static inductance L o , a recent paper suggests that there is in fact an optimum L o below which although the peak total current increases progressively the pinch current and consequently the neutron yield of that plasma focus would not increase, but instead decreases. This paper describes the numerical experiments and results that led to this conclusion.