Propagation of a slow optical deflagration wave in air in a neodymium laser beam

An investigation was made of the large-scale propagation and sustainment of an optically thin atmosphericair laser plasma in the slow combustion regime over a length of up to 20 cm for ~5 msec using neodymium laser radiation of energy 8 kJ. For the first time, an optical discharge was obtained in the slow combustion regime with a steady-state pattern of gas motion. A model is proposed to describe the propagation gasdynamics of the discharge in which the ratio of the observed velocity to the discharge velocity in the gas at rest is equal to the ratio of the velocities of sound in the discharge and in the cold gas. Measurements were made of the front propagation velocities and of the absorption coefficient of the discharge plasma. The thresholds for forced initiation and propagation of an optical deflagration wave in air were determined.