A two-dimensional model of a laser supported hydrogen plasma

A two-dimensional model was developed for a laser supported plasma in hydrogen, based on a model developed by Batteh for air plasmas. Batteh's radiation loss model was modified to include radiation loss from all portions of the plasma. The a priori use of the laser absorption "ignition temperature" was discarded in favor of an a priori choice for the peak temperature of the plasma which is based on the temperature dependence of the laser absorption coefficient.

The model was used to investigate the behavior of laser supported plasmas in hydrogen. The shape of the plasma isotherms and the required laser power was calculated as a function of the hydrogen flow velocity. The axial extent of the isotherms was found to increase almost linearly with flow velocity. The required laser power was also found to increase almost linearly with flow velocity. The dependence of the required laser power on the laser beam radius was also investigated. For smaller laser beam radii the required power was found to approach a constant value, while at larger radii the intensity of the laser was found to be nearly constant. The region of transition from constant power to constant intensity was found to depend on pressure and occurs at smaller radii as the pressure is increased. Finally, the dependence of the required laser power on the value of the laser absorption coefficient was investigated. The required power was found to vary inversely with the laser absorption coefficient.