Dielectric assist accelerating (DAA) structure, which has an extremely high-quality factor (Q0) and a shunt impedance (Zsh) at room temperature, has been proposed and demonstrated the expected cavity properties experimentally. The DAA structure consists of low-loss dielectric cylinders and disks with irises which are periodically arranged in a metallic cavity. The metal wall loss of a higher-order TM02n mode excited in this structure could be significantly reduced as compared with that of a TM01 mode excited in conventional normal-conducting linac structures, leading to high power efficiency. In the experiments, a C-band five cells DAA structure using high-purity magnesia ceramic showed that the Q0 of the accelerating mode was over 105 and the Zsh was 617 MΩ/m at room temperature, respectively.
The advanced techniques for an AVF cyclotron were developed to realize swift and frequent beam switching of the ion species and energy of an ion beam, and to provide highly-stable high-quality beam for special beam formation, such as a microbeam and a single-pulse beam. The high stability of the magnetic field was obtained by controlling the temperature of the magnet iron, and has enabled the fast and reliable beam switching. Based on the highly stabilized magnetic field, the sophisticated techniques for measurement and control of beam-phase and that of reduction of beam phase width by phase bunching in the central region of the AVF cyclotron were developed. Development of the advanced acceleration techniques have realized regular use of the special beams for the research in the fields of biotechnology and materials science.
The production processes of the new types of electromagnet had been developed for the high intensity proton accelerator in J-PARC center. The electromagnets are composed of the high radiation resistance coils with insulating the aluminum strand with polyimide resin or using the mineral insulation cable (MIC). We have heard that the high intensity proton accelerators have been working without any troubles with the electromagnets.
High accuracy alignment of magnets is one of the key issues for next-generation light sources. For the SPring-8 major upgrade, SPring-8-II, and the new 3 GeV light source in north-east Japan, multipole magnets need to be aligned on a straight section with an error of 25 micro-meters in a standard deviation, or within ±50 micro-meters peak-to-peak. With that goal in mind, we have developed a vibrating-wire alignment technique and experimentally investigated its performances. The technique observes the vibration amplitude and phase of a thin wire in the bore of a magnet applied with AC current so that we can directly align the magnetic center on straight without any fiducialization. However, it is necessary to verify the practical performance of the new technique prior to incoming new projects. For example, an imperfection of the wire linearity, including a wire sag and local kinks, may significantly deteriorate the accuracy of the alignment. In this report, we address the main error factors on the precise alignment using the vibrating-wire technique and present our experimental test results to discuss the feasibility of the new technique for future light sources.
The second International School on Beam dynamics and Accelerator technology (ISBA19) was held from 19 to 25 October at Hiroshima International Plaza, Higashihiroshima, Japan. The aim of the school is a gateway of accelerator study for graduate students and young researchers in Asian region, giving an oppotunity to study foundation of beam dynamics and technologies for accelerator studies. We report the school, cocentrating on a new curriculum, Hands-on training for accelerator simulation. We also discuss issues on education in the accelerator field.
The 26th Topical meeting on FEL and High Power Radiation was held at Hiroshima University on Dec. 17 and 18, 2019. Recent achievements have been reported on X-ray and infrared THz free electron lasers, coherent radiation, laser Compton scattering and their applications.