Abstract:
An analysis is made of the difference between the measured velocity of an optical discharge front moving toward the laser source and the theoretical velocity of thermoconductive or radiative propagation of a discharge in a cold gas adjoining directly the front. The difference is explained using a model of flow of a dense cold gas around a hot low-density gaseous sphere. The effect is entirely due to the two-dimensional nature of the motion of gas past the discharge. Only a small fraction of the cold gas enters the discharge, whereas the bulk flows around the hot plasma region as if it were a solid. An optical discharge is modeled numerically for a parallel laser beam in a two-dimensional gas stream. These numerical calculations confirm the results predicted by the simple model. The calculated velocities are compared with the published experimental results.
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