Fabrication and Performance of Superconducting Quarter-Wavelength Resonators for SRILAC

A new superconducting booster linac (SRILAC) at the RIKEN heavy-ion linac is under construction. Ten 73-MHz low-beta quarter-wavelength resonators (QWRs) that operate at 4 K have been fabricated from pure niobium sheets. The cavity parts were assembled by electron beam welding. The resonant frequency for each cavity was adjusted by changing the lengths of the straight sections before welding. The performance and frequency were evaluated by vertical tests. All the cavities exceeded the design specifications of Q₀ = 1x10⁹ and E_{acc} = 6.8 MV/m. Details of the fabrication and frequency tuning as well as the performance of the cavities are reported.
Proceedings of the 19th International Conference on RF Superconductivity, SRF2019, Dresden, Germany