Characteristics of plasma in spatial filter pinhole of high power laser system

The pinhole closure phenomena in spatial filter of high power solidstate laser system might limit the output energy and affect the safe operation of the laser system. The distribution of plasma created by intense laser radiation is studied. The numerical simulation of one dimensional plasma distribution of three typical materials (Al, Au, C) is illustrated. The simulation demonstrates that the diffusion velocity of plasma is about 107 cm/s. The possibility of pinhole closure in the boost amplifier of SG Ⅲ plototype is analyzed, which indicates that the pinhole closure under long pulse laser irradiation is not negligible．