Study on the performance of titanium alloy-lined thin-walled vacuum chamber

HIAF-BRing, the main synchrotron accelerator of the High Intensity Heavy-Ion Accelerator Facility, requires an average pressure lower than 1 x 10-9 Pa and the magnetic field increase rate of no less than 12 T/s to fulfill radioactive beam physics and high energy density physics experiments. To reduce the eddy current effect and the gap size of dipoles, a titanium alloy-lined thin-walled vacuum chamber with a wall thickness of 0.3 mm is proposed by IMP, which has been developed from the initial ceramic-lined vacuum chamber. By mechanical loading testing, when the internal stress of titanium alloy rings made by 3D selective laser melting (SLM) reaches 639 MPa, it is still within the elastic deformation range, in fact, the yield strength of the 3D printed titanium alloy material is 912 MPa. In order to reduce the pressure gradient inside the thin-walled vacuum chamber caused by the surface outgassing of the rings, TiZrV thin films have been deposited on the rings by planar target magnetron sputtering. Through TiZrV deposited on the rings, the pressure at the middle of the thin-walled vacuum chamber has been dropped from 1.5 x 10-9 Pa to 1.0 x 10-9 Pa. At the same time, as the magnets are continuously energized, the actual heating state of the thin-walled vacuum chamber has been also measured.