Wakefield acceleration has been invented to utilize the plasma’s huge collective fields to turn them into a robust, stable, accelerating fields in order to compactify the conventional accelerators by many orders of magnitude. The lasers and beam-injectors have advanced, many proof-of-principle experiments have been realized, and some real world applications have been in practice so far. In the relativistic regime the transverse photon electromagnetic fields can be now turned into longitudinal accelerating fields with the high phase velocity regime realizing very robust structured accelerating conditions even in plasma that some consider as inherently amorphous media. Meanwhile, here we further introduce two new elements, the solid-state media such as carbon nano-tubes (CNT) in place of plasma, while we also look at the regime of high density wakefield acceleration. These combined elements point to a new opportunity of very tiny (on the order of micron) accelerators as well as the control of the phase velocity of wakefields. We envision applications of these tiny accelerators such as to radiotherapy at the tip of an endoscopy.

The discovery of the Kerr lens mode-locking method and broadband Ti:sapphire laser medium, as well as the invention of Chirped-Pulse Amplification (CPA), led to dramatic advances in high-peak power laser technology around 1990. Ultra-high intensity lasers which can produce petawatt (=10¹⁵ W) peak power in femtosecond (=10⁻¹⁵ s) pulse duration in small-scale laboratory settings are now in operation worldwide, and research is being conducted on phenomena that appear under the extreme conditions of ultra-high pressure and ultra-high electromagnetic fields. Here, the technology for amplifying an ultra-short pulse laser and its spatiotemporal control, using the petawatt Ti:sapphire laser system developed at the Kansai Photon Science Institute (KPSI) of the National Institutes for Quantum Science and Technology (QST) as an example will be introduced.

We review theoretical aspects of laser wakefield acceleration (LWFA) with detailed derivation within the linear model and a brief introduction to the nonlinear treatment. We also introduce our project that aims LWFA based X-ray free-electron laser as well as the previously achieved similar projects in the world.

In laser wakefield acceleration (LWFA), high-energy electrons are accelerated by a plasma wave with a wavelength of ～10 µm driven by an intense laser pulse, and a femtosecond electron pulse can be produced. The development of ultrashort X-ray sources using ultrashort electron pulse driven by LWFA has been conducted, and applications to high resolution imaging, observation of ultrafast phenomena and so on have been also demonstrated. In this paper, we review the present status and future prospects of X-ray sources using laser Compton scattering and betatron radiation based on LWFA.

The BELLA Center has been developing the physics and technology of advanced laser plasma accelerators and their applications. This paper introduces experimental R&D work of the Center along with the main laser systems to drive accelerators. The Center’s largest activity has been the development of the laser plasma based electron accelerators for high energy physics applications, and a 10 GeV class laser plasma accelerator has been realized in the Center. Various R&D on associated technologies are discussed as well.

The electrostatic field generated by the interaction of an intense laser and plasma can be used for a compact and ideal ion accelerator. The plasma no longer has the breakdown limitation of solids. Then it creates order of much stronger electric fields that cannot be reached by conventional accelerators. In addition, laser beams can be easily focused to microns scale, making it possible to emit high-current ion beams with low emittance as small as several tens of microns. Laser-driven ion beams are expected to be applied in various fields due to their unique characteristics, and active research is being conducted worldwide to generate higher quality beams. Here, we briefly introduce the characteristics of laser-driven ion beams, the mechanism of ion acceleration, and recent research trends.

The development of laser-driven neutron source (LDNS) utilizing laser-accelerated ions and its application to several kinds of neutron analysis performed at LFEX facility of ILE Osaka University. The LDNS generates neutrons in the wide range of energy from meV to MeV. The main argument of this review is to demonstrate “Single-Shot” neutron analysis by LDNS, where one analysis is accomplished by a single bunch of neutrons generated with a single laser shot. This method enables the high-speed analysis of nuclear information including elements and isotopes.

I took parental leave for about 2.5 months in the spring and summer of 2022. This article describes my experience with the parental leave and with the work I had to do before I went on leave. As long as the duration of the parental leave is known to all concerned and the work is taken over, you can take your childcare leave with peace of mind. Creating handover documents is especially important. This is because you must take over not only in case of injury or illness, but also if you are transferred to a new position. I recommend that you prepare handover documents in advance to ensure peace of mind for both you and those around you. Also, the more important the task, the more you should work together with people of different ages. The timing of life events is different, making it easier for each other to take a paid leave. The parental leave system changed in October 2022. It is now easier to take parental leave than ever before. I hope this will be helpful to men who are considering taking paternity leave and to managers who are thinking about creating a work environment that makes it easier to take childcare leave.

This is a brief report on the 31st International Linear Accelerator Conference 2022 (LINAC2022) that was held at Arena and Convention Centre in the Liverpool, England, between August 28 and September 2.

In order to maximize the performance of accelerators and to make them available for social use, it is essential to improve the control technology of accelerators. Manual tuning has a limit to the number of parameters that can be handled, and it is easy to fall into local maxima. Therefore, we developed a system that automatically tunes multiple parameters simultaneously by using machine learning technology. In this study, we first demonstrated the usefulness of Bayesian optimization by simulating hollow beam transport. After that, we conducted an experiment to tune the ion source by Bayesian optimization. In the experiment, four parameters (gas valve, RF frequency, RF power, and intermediate electrode) were tuned simultaneously, and it was shown that the beam brightness could be tuned as an index in about 1.5 hours.