A newly designed high-performance-type plasma jet device for processing has been developed. This device can generate a high temperature and clean plasma jet and inject the process material into the center of the arc column. In order to demonstrate the application feasibility of this device to thermal processing, the effects of nozzle diameter and material loading on the characteristics of the arc and plasma jet were studied. On increasing the nozzle diameter, the jet power decreases by 0.5-1 kW but the stable operating region expands. In addition, this device operates stably with material loading. It is confirmed that the new type of device proposed would be very useful for various material processes. (C) 2003 Elsevier Science B.V. All rights reserved.