To meet the stringent requirements of high-current energy recovery linacs (ERLs), a 1.3 GHz 7-cell superconducting cavity was designed and optimized. The RF design employed multi-objective optimization to balance accelerating mode performance with higher-order mode (HOM) damping, achieving effective HOM suppression without compromising the fundamental mode performance. Key RF components, including the fundamental power coupler antenna and HOM absorbers, were optimized. Based on the optimized geometry, mechanical analysis was conducted to evaluate structural strength, pressure and tuning sensitivities, and modal behavior. Optimization of the stiffening ring radius further enhanced mechanical stability and reduced frequency variation. The integrated RF and mechanical studies demonstrate that the proposed cavity fulfills the performance and reliability demands of high-current ERL applications.

Recently, the SHINE Linac layout has been modified to use fewer cryomodules (CMs) to reach 8 GeV, bene-fiting from the higher performance of high-Q cavities and CMs. The mass production of SHINE cavities and CMs is currently underway. To date, more than 100 mid-T baked cavities and 100 N-doped cavities have been vertically tested. Most of them have been assem-bled into cryomodules, achieving high Q and quite high gradient in horizontal test. These high-Q CMs are being gradually installed into the Linac section. Two 3.9 GHz CMs have been assembled and tested, demonstrating excellent RF performance. This paper will report the progress in the production and performance of the cavities and CMs.

To meet the stringent requirements of high-current energy recovery linacs (ERLs), a 1.3 GHz 7-cell superconducting cavity was designed and optimized. The RF design employed multi-objective optimization to balance accelerating mode performance with higher-order mode (HOM) damping, achieving effective HOM suppression without compromising the fundamental mode performance. Key RF components, including the fundamental power coupler antenna and HOM absorbers, were optimized. Based on the optimized geometry, mechanical analysis was conducted to evaluate structural strength, pressure and tuning sensitivities, and modal behavior. Optimization of the stiffening ring radius further enhanced mechanical stability and reduced frequency variation. The integrated RF and mechanical studies demonstrate that the proposed cavity fulfills the performance and reliability demands of high-current ERL applications.

1.3 GHz 3-cell superconducting cavities were proposed for the injector of the high-brightness free electron laser based on energy recovery linac scheme. The average beam current is 10 mA and injector energy is 10 MeV. The beam tube of the cavity is enlarged to damp higher-order modes (HOMs) and to keep beam stability. Three cavities have been fabricated. An intrinsic quality factor of 2.0 × 10¹⁰ at 12.0 MV/m and a maximum accelerating gradient of 25.6 MV/m were achieved in the vertical test of the first bare cavity. Design, fabrication, surface treatment, and rf test results will be presented in this paper.