Main RF System for the Hefei Advanced Light Facility

Abstract The main RF system of the Hefei Advanced Light Facility (HALF) is based on superconducting RF (SRF) technology operating at 499.8 MHz. A single-cell niobium cavity has been fabricated and characterized through vertical acceptance tests, which demonstrated an unloaded quality factor Q0 = 1.73 × 109 at an accelerating voltage of 2.0 MV, significantly exceeding the design specification of Q0 ≥ 5 × 108 at 1.5 MV. Two fundamental power couplers (FPCs) have been manufactured and assembled; both low-power and high-power tests were completed successfully, with all measured parameters meeting the design requirements. Additionally, the cryostat, waveguide transmission line, circulator, and RF load were fabricated and validated through factory acceptance tests. The SRF cryomodule is currently in the integration and assembly phase with horizontal testing scheduled for August 2026.