High-current, heavy atom beam system for plasma diagnostics

Abstract

This work describes the results of testing the heavy atom-beam source of the injected internal target technique (IT)2 diagnostic system. The (IT)2 device measures the localized electron density ne and the localized electron temperature Te of a hot electron plasma. The measurement of the spatial distribution of Te is afforded by the local enhancement of x-ray emission (bremsstrahlung) when a beam of high-atomic-number target atoms are injected into a hot electron plasma. Also, the intensity of the emission at the Kα energy of the injected target atoms is a measure of the hot electron density. The (IT)2 measurements require effective beam current densities of 15.0–50.0 mA/cm2 over 20.0–50.0-keV energy range. The beam system used in this work uses ≲2.0 kW of rf power at 2.83 MHz to generate a Xe plasma ion source. A total Xe atomic beam current of ∼15.0 mA at 20.0 keV with an angular divergence of <2.0° is produced after extraction, acceleration, and neutralization of the Xe ions. The ion optics of the beam source are not optimized and improved beam characteristics should be achievable.