enhancement of charge particle emission from a plasma focus device

Abstract

Design and optimization of a low energy plasma focus for enhancing charged particle emission and x-ray radiation from the plasma focus device have been investigated. The design concept and the technical details are described. Design and fabrication of the required diagnostic instruments used to monitor the emitted charged particles and x-rays radiations are presented. The effects of working gas on pinching regimes of the device and generation of charged particle and x-ray radiation have been investigated. Hydrogen, nitrogen, and argon have been used as working gases. The energy spectra of the ions generated in three operating gases depend on the capacitor bank voltage and the effective charge of the ions. The duration of the current drop and the injected energy into the plasma increases significantly in the high-z gases such as argon. Based on discharge circuit analysis of the device it has been found that the plasma resistance reaches 0.2 ohm during the post pinch phase in argon plasma and this anomalous resistance causes significant energy consumption during this phase. It has also been found that the anomalous Joule heating during the post pinch phase enhances the production rate of the runaway charged particles due to reduced Dreicer field. It has been found that the runaway electron generation conditions in tokamaks and plasma focus devices are consistent in terms of the ratio of the electric field across the plasma to the electron plasma density. To enhance the efficiency of plasma focus device as a charged particle source, a new configuration of a dense plasma focus device with three electrodes has been designed and tested. The preliminary experimental results have demonstrated that the new device can produce several focusing events in a plasma focus device. The ion beam emission and hard x-ray radiation pulses last longer than that is expected in a conventional plasma focus and their intensities are also higher.