Application of Nuclear Emulsion to Neutron Emission Profile Diagnostics in the National Spherical Torus Experiment

The technology for OPERA experiments in neutrino physics was applied to neutral-beam-heated deuterium discharges of NSTX in order to measure d-d neutron emission profile. The diagnostic system consisted of nuclear emulsions named OPERA films and the automatic track scanning system S-UTS developed in Nagoya University. A neutron collimator having three channels was temporarily built for this purpose. The nuclear emulsion indicated peaked neutron emission profiles at the plasma center in NSTX as expected

Laser-driven multi-MeV high-purity proton acceleration via anisotropic ambipolar expansion of micron-scale hydrogen clusters

強力なレーザーを使ってエネルギーがそろった純度100％の陽子ビーム発生に成功 --レーザー駆動陽子ビーム加速器の実現へ向けて大きく前進--. 京都大学プレスリリース. 2022-10-13.Multi-MeV high-purity proton acceleration by using a hydrogen cluster target irradiated with repetitive, relativistic intensity laser pulses has been demonstrated. Statistical analysis of hundreds of data sets highlights the existence of markedly high energy protons produced from the laser-irradiated clusters with micron-scale diameters. The spatial distribution of the accelerated protons is found to be anisotropic, where the higher energy protons are preferentially accelerated along the laser propagation direction due to the relativistic effect. These features are supported by three-dimensional (3D) particle-in-cell (PIC) simulations, which show that directional, higher energy protons are generated via the anisotropic ambipolar expansion of the micron-scale clusters. The number of protons accelerating along the laser propagation direction is found to be as high as 1.6 ±0.3 × 10⁹/MeV/sr/shot with an energy of 2.8 ±1.9 MeV, indicating that laser-driven proton acceleration using the micron-scale hydrogen clusters is promising as a compact, repetitive, multi-MeV high-purity proton source for various applications

Development of nuclear emulsion for muography

Muography (cosmic-ray muon radiography) is the non-destructive inspection by using muons produced by interactions between primary cosmic-rays and the Earth’s atmosphere. The principle of this technology is the measurement of absorption of incoming cosmic-ray muons, just like x-ray imaging technology. A nuclear emulsion is the high sensitive photographic film used for detection of three-dimensional trajectory of charged particles such as muons with the position resolution of sub-micron. A nuclear emulsion has following properties: high spatial resolution with thin detector structure, lightweight, flexibility of detector size and no requirement of electric power supply. These properties of a nuclear emulsion are suitable for a detector of muography. We are developing the nuclear emulsion at Nagoya University. In this paper, the current performances of the nuclear emulsion and the fully self-production techniques developed at Nagoya University are described

Analysis Method of Laser-accelerated Sub-GeV-class Proton Tracks in Emulsion Cloud Chamber using Deep Learning Technique

In the interaction between intense laser and the target matter, near-100-MeV proton acceleration is demonstrated. It offers that the potential to realize a energy saving compact particle accelerators in the future. To understand the acceleration process mechanism, precise measurement of both the energy spectrum and the two-dimensional distribution is required. Against this background, we have developed a new measurement method for laser-accelerated sub-GeV-class protons using the nuclear emulsion. Based on the Multiple Coulomb Scattering (MCS) method in an Emulsion Cloud Chamber (ECC), which is a stack of nuclear emulsion films and scatterer plates, the incident energies were inversely evaluated by the scattering angle. The proof-of-principle simulation has been conducted with GEANT-4 Monte Carlo code. To analyze the proton tracks, we have applied the deep learning technique to obtain the incident energy from the amount of MCS in each layer of nuclear emulsion. The median of energy determination coefficient is 0.73 with ramp activation function. The coefficients of the present studies are equal or smaller than the conventional regression model, and we are trying to improve the determination coefficient by optimization of the calculation conditions.ICMaSS202

Application of a nuclear emulsion to laser-driven ion acceleration experiment using micron-sized hydrogen cluster target

A nuclear emulsion is one of photographic films, which can record the three-dimensional trajectories of charged particles. It has the special features of sub-micron spatial resolution and high sensitivity, so that it has been utilized for various research fields. In laser-driven ion acceleration, etched type track detectors such as CR-39 are used as the ion detector to understand the both of spatial distributions and energy spectra. Although the CR-39 detectors are the most reliable detector for laser-accelerated ions, other track detectors, which can crosscheck the results of CR-39 detectors, have not been applied for laser-driven ions acceleration experiments. In the present study, to evaluate the applicability of a nuclear emulsion for the measurements of laser-accelerated ions, we have applied a nuclear emulsion for the laser-driven ion acceleration experiment using micron-sized hydrogen clusters.第14回放射線モニタリングに係る国際ワークショッ