The PF-1000 plasma-focus (PF) facility equipped with Mather-type coaxial electrodes was modified by the addition of a cathode disk in front of the anode front plate, at a distance of 3 cm and by ...covering the hole in the anode center. In comparison with the earlier electrode setup, important differences as regards neutron, X-ray, and interferometric diagnostics were observed for this special electrode configuration. The total current during the pinch phase increased on average by about 25%, the total neutron yield decreased to about 20-30%, and the velocity of transformation of the structures in the column (together with constriction) was evidently depressed. The average energy of the electrons and deuterons produced was decreased. The lower energy value of fast deuterons and their lower cross section of fusion DD reactions were probably the reason for the observed decrease in the total neutron yields.
A PF-1000 device working with a deuterium gas filling and a current on the order of 1 MA was used for studies of the pinch-column structure by means of a laser interferometric system at a period of ...hard X-ray (HXR) and neutron production. Three different phases of the plasma-column evolution, corresponding to the intense HXR and neutron emission, were studied for discharges with neutron yields equal to about 10 11 neutrons/shot. First, the start of the stagnation of a pinch column was considered; as the second phase, the development and disruption of constrictions was studied, and as the third phase, the decrease of the plasma density in a part of the plasma column during its stagnation was considered. Regions of the probable electron and ion acceleration and possible neutron production were identified.
Energy transformations are estimated from experimental results obtained on the PF-1000 plasma focus facility operated with a deuterium gas filling and maximum current of 2 MA, which enabled the ...neutron yield of >; 10 11 to be obtained. Use was made of the laser interferometry images and the recorded signals of hard X-rays (HXRs) and neutrons, as well as voltage, current, and current-derivative waveforms. The calculations of the inductance, derivative of inductance, and resistance of the current sheath enabled the evaluation of energy delivered to the plasma. It was estimated that, during the intensive pulses of the HXRs and neutrons, energy of 3-11 kJ is delivered to the plasma column probably through an anomalous resistance at the time closely before and during pulses of HXR and neutron production. A predominant portion of this energy is effectively used for the acceleration of fast deuterons capable of producing fusion neutrons.
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