Correlated deuteron energy spectra and neutron yield for a 3 kJ plasma focus

Abstract

A magnetic spectrometer positioned on the axis of a 3 kJ plasma focus device has been used to measure energy spectra of deuterons emitted from the pinch region of the focus, while an indium activation detector was employed to measure the associated neutron flux. Solid-state nuclear track detectors (PM-355) were used in the focal plane of the spectrometer to detect the analysed ions, with multiple spectra being recorded on each detector. An automated track counting system has been developed to read the spectral information from the detectors, which has facilitated the analysis of a far greater number of energy spectra, with greater accuracy, than has been possible in previous work. This automated system comprises an optical microscope with CCD camera, a motorized microscope stage, and image processing and control software. The experimental results show that the deuterons emitted from the pinch region have a continuous spectrum of energies which follow the empirical relationship dN/dE∝E-n, where n is typically in the range 6-7. A clear correlation between the measured deuteron energy spectra and neutron flux is observed at each of three working gas pressures investigated.