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

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.