Fundamental characteristics of the hollow cathode arc as welding heat source

A feasibility study has been conducted to determine whether the Hollow Cathode Arc (HCA) can be used for a welding heat source in space, that is with high vacuum and microgravity conditions. The HCA is a low pressure arc discharge, which is formed under low pressure conditions by purging a small amount of gas through the center of the hollow cathode. Investigations into the characteristics of HCA have been experimentally performed. In the present paper, fundamental characteristics of the HCA in a vacuum chamber, such as volt-ampere characteristics, melting properties and plasma properties, have been investigated. Results show that, under the condition that the gas flowrate is low, the HCA column is concentrated under the cathode and the HCA is characterized by a high arc voltage and a high electron temperature. Regarding melting properties, penetration profiles for the HCA melting are sensitive to gas flowrate, and deep penetration can be formed if the gas flowrate is low.