Basic technologies to miniaturize electron accelerators by means of laser plasma acceleration has been developed until JFY2018 under the ImPACT program supported by the cabinet office of the Japanese government. A dedicated experimental platform with sub-petawatt multi-beam laser system was built in RIKEN SPring-8 Center and staging acceleration of electrons was confirmed. Synchrotron radiation was generated with a short period undulator and a conventional electron accelerator. Miniaturization of high-power solid-state pulse lasers has been promoted as well. These developments could contribute to realize ultra-compact electron accelerators and X-ray free electron lasers (XFELs) in future.

An X-ray free-electron laser (XFEL) is a high brightness X-ray source with spatial coherence and a few femtoseconds duration and is now used in various scientific fields. If the size of such XFEL facility is downsized, there would be a high impact not only in science but also in industry. Here, we investigated a conceptual design of a compact 1-keV XFEL with a scale of 10 m based on laser wakefield acceleration (LWFA). By improving the beam performance 10 times compared to the currently achieved parameters in LWFA, we can envision such a compact XFEL. There would be other solutions than improving the parameters. For example, we can use a novel amplification of X-rays by taking advantage of correlated electron beam characteristics in LWFA.

We aim to develop a novel technique to produce a high energy γ-ray beam of several GeV by adopting inverse Compton scattering of soft X-rays at an electron storage ring. Now an experimental project to demonstrate such a beam is being advanced at NewSUBARU by using X-rays from a short undulator and reflecting it backwardly with a Mo/Si multi-layer mirror. It will open up a way to construct new γ-ray sources at the next generation rings and to carry out new photoproduction experiments for the studies of heavy hadrons.

Accelerator technique for neutrons is discussed in this article. In the case of pulsed neutrons, the velocity is well-defined as a function of their arrival time. Electromagnetic neutron accelerator/decelerator synchronized with the neutron time-of-flight is capable of selectively changing the neutron velocity and concentrating the velocity distribution. Possible enhancement of the neutron intensity at a specific neutron velocity is calculated by using numerical simulations. This technique, for example, can be applied to efficient conversion of ultra-cold neutrons with superfluid helium.

The elementary particle physics has been progressing with developments of energy-frontier accelerator projects. The luminosity upgrade of the LHC experiment is scheduled, and discussions on further energy-frontier experimental projects are ongoing among the worldwide high energy physics community. In this article, I review physics motivations for future elementary particle physics experiments with special emphasis on the Higgs physics, and describe status and prospects of two planned projects, namely International Linear Collider (ILC) and Future Circular Collider (FCC).

SuperKEKB is an electron-positron collider located at the High Energy Accelerator Research Organization (KEK) in Tsukuba. The electron cloud effects (ECE) have been a serious problem in recent high-intensity positron and proton rings, and the positron ring of the SuperKEKB (the Low Energy Ring, LER) is no exception. Various countermeasures against ECE, such as beam pipes with antechambers and TiN coating on the inner wall of the pipes, were adopted in LER from the beginning. The ECE, however, were observed during Phase-1 commissioning at a lower beam current than expected. Additional countermeasure, that is, magnetic fields in the beam direction, was applied at drift spaces in the ring after the Phase-1. Experiments in Phase-2 and Phase-3 commissioning showed that the threshold of the current linear density for exciting the ECE increased by a factor of at least 2.6 compared to that during Phase-1. Mitigating effects of several key countermeasures were also experimentally re-evaluated using the real ring.

The 10^th International Particle Accelerator Conference (IPAC’19) was held in Melbourne, Australia from May 19 to 24, 2019. The conference was accommodated in Melbourne Convention and Exhibition Centre (MCEC) located in the Southbank of Yarra River. IPAC is known as one of the main international events for the worldwide accelerator community and industry. More than 1,000 delegates and about 70 industry exhibits presented cutting-edge accelerator research and development results together with accelerator facilities overviews. This report introduces highlights of new facilities and upgrade plans of present accelerators, along with the overview of beam dynamics, instrumentations, and accelerator applications. The IPAC’19 presentation materials and proceedings are preliminarily released at https://ipac2019.vrws.de/index.html. Accurate information and details on the topics of interest might be found there.