Essential technologies for achieving high performances in superconducting RF cavities are reviewed. After explanation of many useful experimental results obtained during the R&D phase in 1.3 GHz single-cell cavities, application to 9-cell cavities for construction of actual accelerators are presented. Recent efforts for improving cavity performance and future prospects on superconducting RF cavities are introduced.

Feasibility is studied on the laser stripping injection of H⁻ beam for J-PARC RCS. The injection energy is 400 MeV and the repetition frequency of H⁻ micro-bunch is 324 MHz. Major hurdles to be cleared are as follows. Because necessary magnetic field for the Lorentz stripping of H⁻ ion and the 2^nd excited state of H⁰ atom is no less than about 2 T and too high to install in the injection area. Therefore, photo-detachment using Nd:YAG laser is to be adopted. Because the Doppler effect is weak at 400 MeV, an excimer laser is necessary in order to excite H⁰ atom from ground state to the 2^nd excited state, whose excitation energy is 12.1 eV. Because the momentum spread of the H⁰ beam is ～10⁻³, the laser band width in the particle rest frame is broadened by the Doppler effect and the necessary laser-pulse energy is accordingly increased. In order to supply necessary laser-beam pulse in 324 MHz, a laser-storage ring is to be developed.

In this report, we describe the machine operation in the first 4 months of the Phase 1 commissioning of SuperKEKB. The beam commissioning is smoothly going on. Vacuum scrubbing, the optics corrections and others are described.