Temporal evolution of the shock wave and hot core air in laser induced plasma

The temporal evolution of electric breakdown in air at atmospheric pressure by Nd:yttrium-aluminum-garnet Q-switched nanosecond laser pulses was studied from the nanosecond to the millisecond time scale by shadowgraphy and interferometry techniques. The results were modeled with a gasdynamic code with good agreement. It was possible to simultaneously model the whole evolution of the plasma, the shock wave, and the hot core air. The shock wave velocity was determined to be greater than or equal to 60 km s(-1) at 20 ns. The plasma temperature was found to reach about 1.7x10(4) K at 1 mus and the hot core air temperature was determined to be < 10(3) K at 100 mus. This letter presents an experimental work that extends the study of laser induced plasmas to millisecond time scales. (C) 2000 American Institute of Physics. [S0003-6951(00)00746-4].