Dynamics of Ring-to-Volume Discharge Transition in H Mode in Inductively Coupled Plasma Torches at Atmospheric Pressure**Supported by the National Natural Science Foundation of China under Grant Nos 21377133, 11535003 and 11505223, the Provincial Science and Technology Major Project of Anhui Province under Grant No 17030801035, and the Science and Technology Service Network Initiative of Chinese Academy of Sciences.

Abstract

The transition process in ring-to-volume discharge in H mode in inductively coupled plasma torches at atmospheric pressure is investigated by analyzing the time resolved image taken by a high speed camera. The effects of input power, plasma working gas flow rate, and its composition on the transition dynamics are also discussed. The results show that the discharge plasma has experienced ring discharge, and the development stage diffused from the boundary to the center in the confinement tube, and steady volume discharge after entering the H mode. Increasing input power, sheath gas flow rate and hydrogen contents in plasma working gas are all able to lessen the time consumed in the transition process in ring-to-volume discharge.