Study on properties of NEG deposited on the titanium alloy lined vacuum chamber

A ramping rate of 12 T/s is designed for the dipole magnet of BRing at HIAF. To reduce eddy current effects, a titanium alloy lined chamber with a 0.3 mm titanium alloy inner liner by 3D printing and an ultra-thin stainless steel outer wall has been adopted. To reduce the internal pressure and enhance the beam lifetime, a film of TiZrV is coated on the chamber. The ultimate vacuum of the titanium alloy-lined vacuum chamber is tested, which indicates that after coating with TiZrV, the pressure at the middle of the chamber reduced, effectively reducing the pressure in the central region. The life of the TiZrV film was studied by repeated activation and venting cycles under two conditions of N2 and air filling. With N2 filling, after 15 activation cycles, the vacuum in the middle of the chamber showed no significant change. However, with air filling, after 7 activation cycles, the vacuum in the middle degraded, indicating a decline in the pumping performance of the TiZrV film. Air exposure significantly impacts the life of the film, necessitating that TiZrV films be protected with N2 in applications and minimizing exposure time.