Electron Energy Distribution Function of the LaB6 Hollow Cathode Tube

Abstract

Much work has been done to understand basic properties of plasma due to hollow cathode discharges. However, these various work are almost specialized either in the hollow cathode glow or in the hollow cathode arc. Since the discharge characteristics are largely dependent on experimental conditions, such as device configuration, species of working gas, gas pressure, and discharge current, it is difficult to discuss in both types of the discharge regime. A new type of a simple LaB6 hollow cathode tube allows us to have very stable discharge even in the regime of the glow-arc transition at the low temperature operation. Because of the relatively large size of our device (25mm diameter) and stable discharge, we were able to investigate various plasma parameters of our plasma in detail by employing a standard Langmuir probe technique and flowing ion current from the cathode orifice (1mm diater). In particular, we have made an extensive investigation of the electron energy distribution function (EEDF) in order to understand the basic characteristics of the hollow cathode discharge. Also, we clarified the critical point which are distinguished the discharge conditions of the abnormal glow, transition, and arc regime. The EEDF of the center of this tube measured by a standard Langmuir probe is the anomalous properties in this transition: another peak appears and disappears in the range of 1-4eV.