Characteristics of Hollow Cathode Arc Plasma as a Heat Source. Investigation into Melting Mechanism Focusing on Electron Density and Temperature.

Abstract

A feasibility study has been conducted to determine whether Hollow Cathode Arc (HCA) can be used for a welding heat source in space. The HCA method enables an arc discharge to ignite and maintain under low pressure conditions, where it is extremely difficult for the conventional Gas Tungsten Arc (GTA) method to form an arc discharge. In the previous paper, it has been demonstrated that the melting process by HCA under the condition that the gas flow rate is high (1.7ml/s) is significantly dominated by the diffuse anode and is characterized by shallow penetration, and that the electron temperature is about 1200018000K in arc space. In the present paper, the volt-ampere characteristics and the plasma property of HCA under the condition that the gas flow rate is low (0.17ml/s) have been made clear, and the melting phenomenon have been discussed. The results are summarized as follows, (1) The HCA under the condition that the gas flow rate is low is characterized by high voltage and high electron temperature, and the arc column is concentrated under the cathode.(2) The electron temperature is above 60000K near the arc axis.(3) The electrons with high temperature, that is high energy, contribute to the deep/huge penetration under the condition that the gas flowrate is low.