Optimization of disposable debris shield in high-energy PW laser focusing system

In inertial confinement fusion laser device, the disposable debris shield is necessary to protect expensive optical elements from the contaminations of target debris when high-energy PW laser was focused in the terminal focusing system. While the shield plate will have a very important impact on the focusing quality. In this paper, the design of debris shield, in high-energy PW focusing system, is studied by optical transmission theory, and the design parameters, such as PV value of wavefront, thickness and installation position of shield plate, are optimized. If 95% of the focal spot energy is concentrated within 10DL, the B-integral introduced by the debris shield should not exceed 8.5 rad when the plate is placed at 0.1f from the parabolic mirror. When the laser power is 1PW, the installation position of 3mm shield cannot exceed 0.29f. The influence of wavefront PV value on energy concentration of focal spot is little. A 3mm shield plate has good damage resistance on light field modulation when its size over 350μm. And the thinner the thickness is, the better the resistance is. This work is important for the arrangement and optimization of disposable debris shield in high-power PW laser focusing system.