Design of a pre-slit for SPring-8 undulator beamlines

A volumetric heating method is applied to the pre-slit placed on the SPring-8 standard-undulator beamline front ends in order to handle the very intensive photon beam. A graphite block is used as the radiation-absorbing body, which is brazed to a cooling holder made of oxygen-flee high-conductivity copper. Various experiments and calculations have been carried out on the strength of the brazed joint. Comparisons between the experiments and calculations show that static fracture of the joint would not occur even under the highest heat load. The outgassing properties of the graphite blocks are also presented here.