Characteristics of Hollow Cathode Arc as a Welding Heat Source -Measurement of Electron Density by IR Method of Plasma Diagnostics

Hollow Cathode Arc (HCA) was developed as a plasma source under the condition of low pressure in the 1960s, and various researches were performed to make clear the mechanism of the HCA. Since the HCA is a discharge under low pressure environment, it attracts attention as a welding heat source in space. Moreover, the HCA is expected to be useful for the industrial application on the earth, because the melting process by HCA is very active and the penetration is huge in comparison with that by the conventional GTA. In the previous paper, it has been shown that the HCA configuration and the melting process by HCA are very sensitive to process parameters, such as gas flowrate and ambient pressure. In the present paper, the electron density distribution of HCA has been measured by IR method of plasma diagnostics (IR method). It is concluded that the beam like core of electron density is formed on the arc axis in the case of low gas flowrate, and the huge penetration by HCA is closely related to the beam like core.