Experimental studies on nonequilibrium plasma flow in a convergent–divergent magnetic field

Abstract

We applied convergent–divergent (C–D) magnetic fields to nonequilibrium argon and hydrogen plasma flows, and investigated the variation of the plasma properties by emission spectroscopy measurements. From the observation of the emission patterns, the C–D magnetic field is found to compress and squeeze the plasma flow, causing the emission region to elongate downstream. It is clearly shown from the captured images that the extent of the compression and squeeze gets larger by applying a stronger magnetic field. Emission spectroscopy of argon plasmas shows that the electronic excitation mode is almost frozen. Emission spectroscopy of hydrogen plasmas shows that the rotational temperature decreases downstream, whereas the vibrational mode is almost frozen. Furthermore, it is demonstrated that the heat loss from the wall can be reduced with the applied C–D magnetic field, because compression and squeeze by the applied magnetic field keeps the plasma away from the wall.