Stability design of support systems in ICF lasers

Abstract

Within Inertial Confinement Fusion (ICF) laser systems, many independent laser beams are required to be positioned on target with a very high degree of accuracy until shots are complete. Optical elements that are capable of moving a laser beam on the target must meet the pointing error budget. Optical elements are typically supported by systems which consist of mounts, mount frames, support structures, and foundation. The stability design for support systems in ICF laser have been developed based on the designing and evaluating experience of ShenGuangIII (SGIII). This paper will provide the methodology of position error budget. The stability allocation is developed for evaluating the performance of support systems when they are subjected to multiple sources of excitations that can cause the motion of optical elements during alignment procedures and before shots. The vibrational stability design considerations of support systems are discussed on the fundamental frequency, ambient random vibration, and modal damping. The support structures of optical elements are the relatively large and massive hybrid structure of reinforced concrete and steel frame or vessels. While the reinforced concrete portions provide optical elements stability, the steel portions afford design flexibility. Finite element analyses of ambient random vibration are typically performed to evaluate the vibrational stability performances of support systems. Finally, this paper describes the ambient random vibration and beam pointing error measurements of SGIII. The measurements show the support systems of SGIII meet design requirement. These information can be used on similar systems.