Large-aperture alumina ceramics beam pipes with titanium bellows for the rapid cycling synchrotron at Japan Proton Accelerator Research Complex

The 3-GeV rapid-cycling synchrotron at the Japan Proton Accelerator Research Complex aims to generate proton beams whose power output is among the highest in the world, reaching an extraction beam power of 1 MW. Beam pipes fabricated using alumina ceramics are used to prevent the formation of eddy currents caused by the rapid magnetic field changes. The residual radioactive dose is higher in the beam-injection area than in other areas. In this area, ceramics beam pipes in a quadrupole magnet and a horizontal bump magnet are directly connected without bellows because of space limitations. Improvement of the maintainability of such areas is the first priority for minimizing the radiation exposure of maintenance workers. The ceramics beam pipe in the quadrupole magnet was custom designed to have bellows on both ends. The shapes of the ceramics end unit ducts and titanium sleeves of the pipe was revised to allow a 30-mm long space for inserting the bellows. The ceramics unit ducts and titanium sleeves with un...