Behavior of underexpanded plasma jet in strong magnetic field

A visual study of underexpanded plasma jet was conducted to reveal the detailed behavior in the strong magnetic field. The images of the jet were taken by a digital single-lens reflex camera through viewing windows. The distribution of optical intensity obtained from the raw data was compared to that of the typical emission line intensity. The profile of the optical intensity agrees well with that of the emission intensity. It is illustrated that the typical structure of underexpanded jet such as Mach disk is also affected obviously by the magnetic field. The radial distribution of number density was determined by using the image analysis based on the Abel-inversion. The converted data clarify the jet behavior that is hidden on the ordinary observation. The density obtained from numerical analysis for a simple gas was also compared with the number density. It is confirmed from the comparison with numerical results that the radial profile of number density can be utilized for understanding the plasma jet behavior under the strong magnetic field.