Measurements of high-energy deuterons in the plasma-focus device

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Abstract
Nuclear activation techniques have been used to measure the fluence of high-energy deuterons in a plasma-focus device. Substantial activation of carbon and aluminum targets was observed on most shots where the deuterium pressure was less than 3 Torr. Carbon activation indicates more than 1015 deuterons above 330 keV on some high-intensity shots. These deuterons are strongly forward directed with 0° to 90° ratios exceeding 104 on high-yield shots. Ratios of 13N to 28Al, foil-stack activation measurements, and neutron time of flight all consistently show some deuterons have energies above 2 MeV. Measured 13N/28Al ratios also indicate more than 1012 deuterons of energy greater than 5 MeV, but this result has not been verified by an independent threshold-activation measurement. These measurements illustrate that the plasma-focus device can be operated in two distinctly different modes, with low-pressure operation resulting in the acceleration of ions and electrons to many times the capacitor-bank charging voltage. Most of the neutron emission in low-pressure operation may come from beam-target reactions.