Design of the NSLS infrared beamline mirror number 1

Abstract The mechanical design of the infrared beamline mirror #1 (IRBL M1) at the NSLS facility was done with the aid of finite element modeling. Preliminary heat load calculations indicated that the Gaussian peak power density incident on M1 is ∼ 345.8 W/cm 2 . The thermal gradient due to the this concentrated high heat density striking M1 may result in undesirable distortions that can seriously impair its function. In addition, the thermal stress might reach levels beyond the yield strength of the mirror thereby compromising its structural integrity. Hence, a finite element model was developed to study the associated thermal and structural problem. The generation of the finite element mesh was done with the PREP7 module of ANSYS [1]. After applying the appropriate parameters and boundary conditions, a thermal analysis was performed and the results were passed into the structural model in order to obtain the displacement/stress solution. A similar finite element model was analyzed using SUPERTAB and SUPERB of SDRC's IDEAS [2]. Since the mirror, obviously, needs an active cooling loop, various cooling design schemes were explored during the numerical analysis. In order to avoid further complications during full power operation, it was decided that the mirror be kept as an independent free body sandwiched in between two chilled blocks. The heat transport process then becomes a function of the characteristics of the interface between the mirror and the chilled blocks. In the previous report [3], the advantage of using a silicon carbide mirror was described chiefly based on the experience of the laser community. Therefore, using the finite element model that was developed for M1, we compared the performance of silicon carbide and copper mirrors under identical operating conditions. We will present the results of the analysis as well as the final design of the IRBL mirror #1.