We stress in this review paper that we should describe synchrotron oscillations using the length s of the central design orbit as an independent variable. A symplectic theory in this case is already available and we can incorporate important nonlinear features into the theory that are lost if we use the time t as the independent variable. We also settle the arguments about a closely related problem of the effects of betatron acceleration on synchrotron oscillations; the betatron acceleration affects not only the energy, but also the phase (arrival time) of the particles. When the equations for these two quantities are combined to form a second-order phase equation, the effects are cancelled in the adiabatic approximation.

A superconducting rotating-gantry for carbon-ion radiotherapy was developed. This isocentric gantry can transport carbon ions having kinetic energies of between E=430-56 MeV/𝑢 to an isocenter over an irradiation angle of ±180 degrees, and is further capable of performing three-dimensional raster-scanning irradiation. The rotating gantry equips combined-function superconducting magnets. Since these magnets can provide both dipole and quadrupole fields, no quadrupole magnet is required for beam focusing. Having used the combined-function superconducting magnets and optimized the layout of the gantry as well as the beam optics, the length and radius of the gantry became approximately 13 m and 5.5 m, respectively, which are comparable to those for proton gantries. Construction of the entire rotating-gantry system was completed by the end of September, 2015. Having performed beam commissioning over various combinations of gantry angles and beam energies, we could successfully obtain the designed beam quality, which satisfies the requirements of scanning irradiation. Cancer treatments using the superconducting rotating-gantry were started since May, 2017.

The first hadron collider with superconducting magnet technologies was built at Fermi National Accelerator Laboratory as TEVATRON. Since then, the superconducting magnet technologies are widely used in large accelerator applications. The paper summarizes the superconducting magnet technologies used for large accelerators.

Research Center for Electron Photon Science(ELPH) at Tohoku University had passed fifty years since the establishment of Laboratory of Nuclear Science (LNS) affiliated to the Graduate School of Science, the forerunner of the present center. LNS started in 1966 as a user’s facility available to the researchers in Tohoku University. The pulsed electron beam from the 300 MeV LINAC, which was constructed in 1967, has been widely utilized for not only nuclear physics but also other research fields such as material science and nuclear chemistry. In also the same 1967, experiments with the pulsed neutron generated by the accelerator were started for the first time in the world. Since then a lot of pioneer works had been performed till the termination of the neutron facility in 1993. Furthermore, it was first demonstrated in the world to stretch the pulsed beam from LINAC by a pulse‐stretcher ring in 1981. This ring had led some distinguished researches in nuclear physics and been succeeded to the 1.2 GeV stretcher-booster ring in 1995. After the reorganization from LNS in 2009, ELPH has conducted significant research and educational activities as a part of Joint Usage / Research Centers since FY 2011. In this article we would like to introduce the history for these 50 years up to the commemorating ceremony for the 50th anniversary of the establishment held on the last November, focusing on the vicissitudes of the electron accelerator complex and the roles played at that each time.

A new scheme of short-lived radioisotope (RI) supply for fundamental research in a wide variety of scientific field was started in 2016 under the framework of cooperation among accelerator facilities at RCNP, RIBF, CYRIC and ELPH. The project aims at promoting cutting-edge research supported by Grant-in-Aid for Scientific Research (KAKENHI) by supplying a short-lived RI which is hard to obtain commercially. A research proposal requiring a short-lived RI is collected twice a year and one of accelerator facilities supplies the short-lived RI for the approved proposal according to the user’s requirement. This platform provides technical support for RI treatment and gives beginners an opportunity to learn safe handling of RIs as well.