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.

A technique for the determination of the inductance evolution in coaxial discharges based on measurements of the voltage between the electrodes and of the discharge current time derivative is presented and discussed. The technique is applied to measurements performed in a 5.7 kJ plasma focus device operating with deuterium filling in the 1-6 mbar range (which is the neutron yield range) and the obtained results are in good agreement with the expected evolution of a current sheet within the electrodes system.

The measurement of the voltage between electrodes and the discharge current time derivative in Plasma Focus devices can be used to obtain important information on the neutron-producing pinch stage of the mentioned devices. The analysis of a 60-shots experimental run in a 5.7 kJ Mather-type device results in correlations suggesting that the neutron yield depends mostly on the average energy per particle delivered to the plasma during the pinch stage.

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