Results of Ultracompact Plasma Focus Operating in Repetitive Burst-Mode

Abstract

The results of a miniature plasma focus are presented in this paper which is operated with energy less than or equal to 150 J. The miniature plasma focus is driven by a small capacitor bank and the peak current delivered in the focus is 75-80 kA. The deuterium gas is filled with a pressure range of 5-7 mbar inside the plasma focus chamber. The quartz glass is used for generating initial surface breakdown at a 4-5-kV discharge, which is a typical value for low-voltage plasma focus discharges. The repetitive operation (record 50 Hz) of the device is achieved by a combination of a simple and high power (5 kW) supply with the synchronized triggering of the capacitor bank at the time of isolation between supply and the capacitor bank. The diameter of cathode is 25 mm and anode diameter is 8-12 mm and both of them are made of stainless steel. The length of anode and gas pressure is adjusted in such a way that the pinching occurs at the time of occurrence of the peak of current. It enhances the neutron emission from the device. The time-of-flight diagnostic is used to distinguish neutron and X-ray emission from the plasma focus. The neutron measurement using a helium-3 detector and also a fast-scintillator-backed photomultiplier tube demonstrates production of neutron pulses in the time separated by nearly 20 ms, which corresponds to 50 Hz in the burst mode. The device can serve the purpose of being a portable and compact repetitive neutron source for various applications as the flux of the radiation is comparable with that of bigger plasma focus operating at the similar current.Index Terms-Plasma devices, plasma sheath, pulse power systems.

Development of the dense plasma focus for short-pulse applications

“…Development of the DPF has traditionally focused on maximizing the total fusion neutron yield, [14][15][16] with more recent designs intended to increase portability and pulse repetition rates. [17][18][19][20] In this report, we describe the first efforts to constrain the neutron pulse duration while retaining as much of the total yield as possible. This initial effort focuses on very modest variations on the Mather-type DPF hardware design, specifically the shape of the downstream electrode terminations, without changing the discharge times of the capacitor banks (4 À 7 ls) or the gas constituents.…”