Development of Thin-wall Vacuum Chamber for Heavy Ion Medical Accelerator

Heavy Ion Medical Machine (HIMM), developed by the Institute of Modern Physics, Chinese Academy of Sciences, is the first medical heavy ion accelerator with independent intellectual property rights in China. Because the RAMPING mode was used for high frequency pulse dipole magnets of HIMM and the rising rate of magnetic field is 1.6 T/s, the vacuum chamber installed in the high frequency pulsed magnet is a thin-wall stainless vacuum chamber with reinforcing ribs to reduce the influence of eddy current on the ion beam stability. However, the gap size of magnet occupied by thin-wall stainless vacuum chamber with reinforcing ribs is too large, and it not only causes the high cost of magnets, but also greatly improves the maintenance cost. Based on these reasons, a new thin-wall vacuum chamber (0.3 mm) with ceramic lining was put forward and the prototype was designed and manufactured. The test results show that the obtained pressure of the prototype is in the order magnitude of 10^-10 Pa, and the magnet gap can be effectively reduced. And it is the development direction of thin-wall vacuum chamber of accelerator in the future.