Shock wave in dense gas generated by high power millimeter wave

Oda, Yasuhisa; Kajiwara, Ken; Takahashi, Koji; Kasugai, Atsushi; Sakamoto, Keishi; Yamaguchi, Toshikazu*; Komurasaki, Kimiya*

In this study, millimeter wave (MMW) shock wave was visualized using shadow graph method. The high power MMW beam generated by 1 MW-class 170 GHz gyrotron was supplied into a shock tube which had rectangular section part with visible window. As a result, the shock wave was nearly uniform and straight to the tube section and it propagated in constant velocity. The propagation velocity of shock wave and the ionization front was deduced from series of photographs. As a result, both velocities were 500 m/s and 430 m/s, respectively. Shock wave and the ionization front of plasma were detached to each other. However shock wave and the ionization front were propagated in steady state. Although the shock wave was detached from the ionization front, the MMW plasma supported the shock wave in the tube at steady state. This was because the power absorbed by plasma was supplied to shock wave without loss in the tube.