Physical quantities of coersive force, permeability and saturation magnetization of such ferromagnetic materials as laminations for magnets supposedly correlate to each other in physics viewpoint of ferromagnetism. The correlation affects magnetic field distribution depending on excitation levels because the maximum of permeability appears at a middle excitation level between coersive force and saturation magnetization; so that the correlation is helpful for producing magnets with a wide good field region for a broad excitation range in practice of finishing magnets. Dipole and quadrupole magnets of HIMAC synchrotron had demountable pole end pieces of which thickness and shape were adjustable. The adjustments were based on filed measurements and provided high-quality magnets. Taking the correlation into account, such an excitation curve as I (excitation current) vs BL (integrated filed) was proposed to be a sum of two independent fractional expressions so as to reproduce measurements well.

To stabilize beam intensity and transmission efficiency from an electron linac accelerator to a circular accelerator, it is effective to synchronize two different radio frequencies (RF). A new synchronization method of two arbitrary different radio frequencies was developed and has been stably operated at SPring-8. The method is described.

Neutron is a unique probe to study materials according to its low capability to excite chemical bondings with a relatively high sensitivity to light elements. However, its low luminosity has limited the application fields. The recent innovations in neutron optics have been activating enhanced analyzing capabilities of neutron scattering experiments. We describe the current status of advanced neutron optics and possible extensions of their applications.

Electron cloud effect has been studied for J–PARC RCS (Rapid Cycling Synchrotron) and MR (Main Ring). Numerical simulation shows electron cloud may build-up to the neutralization level of a few %. With a linear theory and numerical simulation, electron-proton (e–p) instability is examined. Electron cloud observation at the KEK–PS is also discussed for comparison. The present investigation shows that e–p instability in the J–PARC rings will be manageable, assuming some remedies such as local solenoid magnets.

The SAGA Light Source (SAGA-LS) is the first third-generation synchrotron light source designed, constructed and operated by the local government, Saga Prefecture, in Japan for the promotion of scientific researches and industrial applications in Kyushu area. The SAGA-LS consists of a 250-MeV electron linac injector and a 1.4-GeV storage ring with eight double-bend (DB) cell and eight 2.93-m long straight sections. The DB cell structure with a distributed dispersion system was chosen to produce a compact and low cost ring of 75.6-m long circumference. The commissioning began on August 24, 2004. The first synchrotron light was observed on November 12. The commissioning goal of 1.4 GeV–100 mA was achieved on August 25, 2005. The SAGA-LS was opened to users in February 17, 2006.

At Kyushu University tandem laboratory, preparation for an experiment of ¹²C+⁴He→¹⁶O+ⲩ reaction at stellar energy has been made since 1994. The experiment is very difficult because the reaction cross section should be measured down to 1 pbarn. Many instruments and methods have been invented and developed. Some of them, accel-decel operation of the tandem accelerator, a windowless gas target, and a long-time chopper, are described.

The International Fusion Materials Irradiation Facility is an accelerator-based high-energy intense neutron source for materials development towards DEMO fusion reactor. The IFMIF accelerator system is required to provide a cw deuteron beam of 40 MeV–250 mA with an extremely high availability, 88%. The key concept for achieving these requirements is an operational stability and some essential features of key components were verified in these years. To complete the engineering design for the decision of future construction, a prototypic low-energy part up to ～10 MeV will be built in the next phase under the European-Japan collaboration.

Hadrontherapy facility PATRO (Particle Accelerator for Therapy, Radiology and Oncology) is constructed in Harima Science Garden City by Hyogo prefecture government. Proton (230 Mev) and carbon (320 MeV/u) beams are used for the cancer therapy. The facility has 3 treatment rooms with fixed beam ports and 2 treatment rooms with isocentric proton gantry ports. The treatment of 1000th patient was accomplished successfully in May 2006.

I arrived in Japan on the first of April 2005 as JSPS fellow, just after graduating at the rf group of the Paul Scherrer Institute (PSI) in Switzerland. I’m now working in the accelerator development group at RIKEN Nishina Center in Wako-shi. Research and life in Japan is very exciting and in some points different from those in Switzerland.