Speaker
Description
NanoTerasu is a newly constructed 3 GeV light source located in Sendai, Japan. The circumference of storage ring (SR) is 349 m and the natural emittance is 1.1 nm rad which is realized by the double-double-bend achromat lattice. The compact normal-conducting RF cavity operating in the TM020 mode with higher-order mode (HOM) dampers is employed for beam acceleration. The commissioning of the SR started in June 2023. However, the longitudinal instability was observed during the SR commissioning in 2023 at a beam current of approximately 150 mA. Although partial suppression was achieved by adjusting the RF cavity temperature, the stored beam current during user operation in 2024 remained limited to 200 mA. To overcome this limitation, a compact waveguide-overloaded kicker cavity and longitudinal bunch-by-bunch feedback (LBBF) system were developed and installed. The commissioning of the LBBF system in July 2025 enabled stable beam storage at the design current of 400 mA. The stored beam current for user operation was subsequently increased, and routine user operation at 400 mA with high reliability began in November 2025. The suppression of longitudinal instability will be presented.
| Paper status | Proceeding files received |
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