Thermal analysis and tests of W/Cu brazing for primary collimator scraper in CSNS/RCS

To the transverse beam collimation system in a rapid cycling synchrotron, an important component is the primary collimator, which improves emittance of the beam halo particles such that the particles outside the predefined trajectory can be absorbed by the secondary collimators. Given the material properties and power deposition distribution, the beam scraper of the primary collimator is a 0.17 mm tungsten foil on a double face-wedged copper block of 121.5 mm × 20 mm. The heat is transferred to the outside by a ϕ34 mm copper rod. In this paper, for minimizing brazing thermal stress, we report our theoretical analysis and tests on brazing the tungsten and copper materials which differ greatly in size. We show that the thermal stress effect can be controlled effectively by creating stress relief grooves on the copper block and inserting a tungsten transition layer into the copper block. This innovation contributes to the successful R&D of the primary collimator. And this study may be of help for working out a brazing plan of similar structures.