An electron in circular motion radiates an electromagnetic wave possessing a helical wave-front and carrying angular momentum other than spin. I discuss the theoretical background of this process and give an intuitive explanation. I also show some evidences from experiments at a synchrotron light source. Radiation from an electron in circular motion is the basis of various important radiation processes, such as cyclotron/synchrotron radiations, Thomson/Compton scatterings of circular polarized light and so on. This finding indicates that vortex radiations in the VUV, X-rays and gamma-rays can be produced by accelerator based technologies. Moreover, it indicates that vortex photons can be naturally created in various situations in the universe.
This year is the 100th anniversary of the RIKEN, the original campus of which was located at Komagome, Bunkyo-ward in Tokyo. There Dr. Yoshio Nishina “the father of Japanese modern physics” initiated “Japanese accelerator-based science” in 1930’s and led to the world top level. But after the defeat, its level had been behind America and Europe. Through the long-time struggles, Japan successfully has caught up them, and now is again on the top level. In this article, I describe briefly a history of RIKEN’s ion accelerators, and looked back over the construction of the RI Beam Factory (RIBF) unparalleled in RI beam production capability, which we proposed and led.
PF-AR is a synchrotron light source located in High Energy Accelerator Research Organization (KEK) and supplies hard X-ray with single bunch operation. The injector “LINAC” of PF-AR is shared with other three rings: High Energy Ring (HER) and Low Energy Ring (LER) of SuperKEKB and PF. In KEKB era, the beam transport line (BT) of PF-AR and HER was shared, and the injection had to be interrupted for ten minutes at least for the standardization of the magnets when changing the objective ring for the injection. In the winter of FY2017, phase 2 operation of SuperKEKB will begin, and its Touschek lifetime is calculated as about ten minutes. This is shorter than in KEKB era, and the sharing of the BT cannot be adopted anymore for the simultaneous operation of both PF-AR and SuperKEKB. In order to realize this, we have constructed a new BT dedicated to PF-AR. The excavation of the new tunnel started in 2013, and the infrastructure construction was completed in 2014. The commissioning with the new direct BT started on 13 February, and the user-run was resumed in April 2017. The machine study for the top-up operation of PF-AR and the simultaneous top-up operation of all 4 rings are planed in autumn 2017 and in autumn 2018 respectively.
EURO-XFEL was constructed to offer the most intense SASE free electron laser (FEL) in x-ray regime at DESY of Hamburg from 2009. I worked in DESY for one year to join the construction of the EURO-XFEL accelerator and to measure the performances of more than 800 1.3 GHz 9-cell superconducting cavities after the cryomodule assembly work in a mass-production phase. Especially, it is important to evaluate how many cavities would be degraded during cryomodule assembly work after the vertical tests. The mass-production of 100 cryomodules with 800 superconducting cavities is the largest scale in the world. In this article, we report my one-year stay at DESY concerning about the EURO-XFEL accelerator construction with this cryomodule test.
Fourth Workshop–Particle Therapy Facility Operation and Maintenance (4th W-PTFOM) was held in Gunma University at June 9, 2017. There were 95 participants from particle therapy facilities, accelerator facilities, and manufacturers. Ten talks concerning case reports of troubles and quality assurance of the machine operation were presented with fruitful discussions.