The vacuum system of the China spallation neutron source

The china spallation neutron source (CSNS) is designed to accelerate pulse proton beams to 1.6 GeV kinetic energy with a beam power of 100 kW at 25 Hz repetition frequency, which are used to strike a solid metal target to produce spallation neutrons. We describe the structure features, technical requirements, design scheme and experimental results of each part of the CSNS vacuum system. The alumina ceramic constructed of isostatically pressed methods is chosen as the material of the dipole and quadrupole vacuum chambers as a result of the rapid cycling magnetic field in the rapid cycling synchrotron (RCS), which were welded by glazing and metallizing, respectively. The inner surfaces of the ceramic chambers were coated with TiN using the magnetron sputtering method in order to reduce the secondary electron yield (SEY); the radio frequency (RF) shielding copper strips were covered around the outer surfaces of the ceramic chambers by a kapton film to decrease the impedance of the image current. The CSNS vacuum system has been installed and tested; an average static pressure of 1.3 x 10(-7) Pa was achieved in the RCS. The average dynamic pressure was 1.1 x 10(-6) Pa when the first beam power reached the national acceptance target of 10 kW at 25 Hz.