Temperature-dependent transition of discharge pattern during helium cryo plasma

Summary form only given. New cryogenic plasma source, so-called cryo plasma was established under atmospheric pressure. Cryo dielectric barrier discharge (DBD) system could easily control processing temperature from room temperature to 78 K by liquid nitrogen. Reactor chamber for this experiment consisted of two chambers, the inner and outer chamber. We employed a DBD reactor into the inner chamber and connected an AC power supply operating at a frequency of 20 kHz. Helium as discharge gas was introduced into the inner chamber and the operating pressure was kept at atmospheric pressure, with a steady state condition. And the outer chamber played a role to control and sustain gas temperature by flowing liquid nitrogen as a refrigerant. After experiments, we found out the plasma properties, such as discharge patterns and color, showed the temperature- dependent behavior as gas temperature went down. And this result was closely related with the change of emission spectra measured by optical emission spectroscopy. Conclusively, the change of gas temperature induced a transition of discharge mode. The detail will be discussed at the conference.