High H Radical Density Produced by 1-m-Long Atmospheric Pressure Microwave Plasma System

We have developed an atmospheric pressure microwave plasma system with a microwave antenna consisting of two microwave guides, which have a discharge line with 41 slots. The antenna is set against a movable stage with a heater in a process chamber. The process gas used is a 1% H 2 gas diluted by Ar gas. We clarified various characteristics, such as gas temperature, electron density, and hydrogen radical density, using this system, and found that the gas temperature is about 1000 K, the electron density is $1\times 10^{15}$ cm -3 , and the H radical density is $1\times 10^{16}$ cm -3 at the slot under the condition of a 10 GHz, 1.5 kW, pulsed microwave with a pulsed voltage of 2.5, a pulsed frequency of 4 kHz, and a duty ratio of 0.16.