Design modification and high-power tests of the 500 MHz normal-conducting 5-cell cavities for HEPS

Abstract The booster ring of the High Energy Photon Source is responsible for ramping the beam energy from 500 MeV to 6 GeV. Six 5-cell copper cavities of PETRA-type were chosen to provide a total accelerating voltage of 8 MV. In order to meet the specific requirements of the HEPS booster, several modifications were made to the original cavity design. Six cavities were delivered to IHEP and underwent successful high-power testing in 2022. The cavities were tested up to a maximum rf power of 120 kW c.w., which is within the reliable capability of the power coupler specified by the vendor. Subsequently, power was maintained at the maximum rf power, with an average duration of 100 hours. Finally, to verify performance during actual operation, a ramped run was conducted according to the pre-defined curve at a repetition rate of 1 Hz, with all low-level rf control loops closed. This paper presents details on the design modifications and the high-power tests of the 500 MHz normal-conducting 5-cell cavities for the HEPS booster ring.