We report on the application of machine learning techniques to enhance the spatial resolution and reproducibility of quantum spin imaging using β -NMR and μ SR methods. Our innovative imaging device, Mr. β RIGHT, visualizes material distribution based on interactions between polarized quantum spins and matter. We demonstrate that machine learning approaches, including linear regression, neural networks, and deep generative models (cVAE and cGAN), improve image reconstruction compared to conventional mathematical analysis. Using Geant4 simulations with up to 200,000 training events, we achieved spatial resolutions better than 1 mm. Notably, deep generative models enable interpretable reconstruction of spatial density patterns even under limited statistics (as few as 100 events), providing a complementary approach to conventional deterministic analysis. These advances open new pathways for dynamic spin imaging and real-time material characterization.

Interaction cross sections σ I for 58–77 Ni on a carbon target at 280 MeV / nucleon were measured at the RIKEN Radioactive Isotope Beam Factory (RIBF) using the BigRIPS fragment separator. The aim of this work is to deduce matter radii from the measured values of σ I through Glauber-model analysis and, by combining them with the charge radii that have been precisely determined by the laser spectroscopy, to determine the neutron-skin thickness r np of Ni isotopes over a wide range of neutron excess δ = ( N Z )/ A from 0.03 to 0.27. The present data of σ I constitute the first systematic set along the isotopic chain in the Ni mass region, providing a consistent basis for investigating the evolution of nuclear size and neutron-skin with increasing neutron excess. The slope of the neutron-skin thickness r np as a function of the neutron excess δ is expected to provide an important constraint on the L parameter of the nuclear matter equation of state (EOS), which represents the first-order term in the density dependence of the symmetry energy in nuclear matter. The EOS is essential for understanding not only the structure of atomic nuclei but also the mechanisms of supernova explosions and the properties of neutron stars. The results of this study are therefore expected to provide valuable insights into the elucidation of the EOS.

The charge-changing cross sections σ_CC have emerged as a promising observable for deducing nuclear charge radii of unstable nuclei. In this study, we measured σ_CC for neutron-rich nickel isotopes ^58–77 Ni at 250 MeV/u. The experimental results were analyzed by using a Glauber model including charged-particle evaporation effects, and the consistency between the measured σ _CC and existing charge radii was investigated. The results demonstrate that the present approach provides a reliable description of σ _CC systematics in the Ni isotopic chain. These findings support the applicability of σ _CC measurements as an alternative probe of charge radii, particularly for nuclei where direct measurements are not available.

The charge-changing cross sections σ _cc of ^10-13 B, ^11-13 C, and ^12,13 N nuclides on multiple targets were measured at the energy of about 170 MeV/nucleon. The point-proton radii of these nuclides were determined by comparing the experimental σ _cc with the Glauber model calculation considering the charged-particle evaporation effect. For ^12,13 B, the present results are consistent with the existing experimental data deduced by different methods.

We have previously measured ^12 B in single crystal diamond by β -NMR; however, the NMR signal was very weak, and approximately 90 % of implanted ^12 B was undetected. In the present study, we measured the nuclear polarization and relaxation of ^12 B implanted in grain-shaped diamonds at 15, 150, and 300 K. More than 20 ^12 B nuclei were found to initially settle at sites that maintained polarization well, and polarization relaxation in the order of tens of milliseconds was observed. This partially explained the very weak β -NMR signal in the previous experiment. A slow relaxation was observed at 15 K in addition to the fast relaxation. The existence of these two relaxations suggested multiple implantation sites.

$$\beta $$ -detected nuclear magnetic resonance ( $$\beta $$ -NMR) is a powerful research tool in nuclear physics and material sciences. In this study, we integrated an imaging function into a $$\beta $$ -NMR instrument. Specifically, we installed position-sensitive detectors to create a magnetic resonance imaging device, which we have named the $$\beta $$ -MRI. We conducted experiments to evaluate the performance of this device by irradiating spin-polarized $$^{12}$$ B beams on a sample, and successfully generated its material mapping image.

A new experimental method to search for T-violating transverse muon polarization ( P_T ) in the K^+ →π ^0 μ ^+ ν decay using an electro-magnetic calorimeter has been proposed. The test experiment to find good scintillating materials was performed at the J-PARC Material and Life Science Facility (MLF), and the residual μ ^+ polarization in a scintillating CeF _3 material was found to be higher than 90 _3 to increase effectiveness of the new polarimeter system in various experiments. A muon spin relaxation/rotation ( μ SR) experiment was performed using a 2 _3 crystal. The time-integrated residual polarization in LaF _3 within the time region of 10 μ s was obtained to be 83 μ SR spectra in the temperature region from room temperature to 328 K were taken to check the reproducibility of the μ SR spectra reported in the previous experiment, in which the rapid transition of the zero-field μ SR spectra was observed at 323 K. The ZF μ SR spectrum obtained at 328 K is in good agreement with that at room temperature, and an obvious change reported in the previous study [8] was not observed in the present work.

The muon spin rotation/relaxation/resonance ( μ SR) spectroscopy is widely used as a unique tool for probing magnetic properties in materials. We aim to enhance this method by incorporating imaging functionality. In this study, we conducted an experiment using a new imaging device that utilizes positron tracking from muon decays to assess the reliability of positron tracking and its positional resolution. As a result, we have demonstrated that an image depicting a hole with a diameter of 5 mm could be reconstructed.

We are developing an active shield for the measurement of neutron electric dipole moment using ultracold neutron. The disturbing geomagnetism and environmental magnetic fields are cancelled by the active shield. We introduced proportional-integral-differential control to the feedback loop of the system to improve the performance of the active shield. A quadrupole-coil arrangement was adopted to control the diagonal components of the field gradient. The influence of magnetic shielding inside the active shield was studied. It was found that this effect caused no critical problems in the detection of zero-field conditions.

Muon spin relaxation/rotation/resonance ( μSR ) method is one of the most effective experimental methods and has been used in many fields such as material science, chemical, and bioscience since the 1970s. For the next elevation of μSR , we developed positron detectors that have a spatial resolution and used them as positron trackers so that we could construct an image of a sample. Demonstrative experiments of trackers were performed at TRIUMF and an image of a sample was successfully reconstructed.

A new experimental method to measure muon polarization using a scintillating material has been proposed. One of the key issues for this measurement is the choice of scintillation materials which can maintain the /4 + spin polarization for several /4 + lifetimes. Thus far, a CeF 3 scintillating crystal has been known to be only a possible candidate and it is highly preferable to find other scintillators whose performance is nearly equivalent to CeF 3 . The residual /4 + polarization in a 2% cerium-doped LaF 3 scintillating crystal was measured at the JPARC Material and Life Science Facility (MLF) by applying the longitudinal field (LF) to the LaF 3 material. The polarization was obtained to be 83 and 87 % with LF = 100 and 140 Gauss, respectively, which is high enough to measure the /4 + polarization in various experiments.

Nuclear magnetic resonance (NMR) using β-decay radioisotopes, known as “β-NMR,” is used for research in nuclear physics. Recently, nuclear magnetic moments of β-decay radioisotopes have been precisely measured by β-NMR. Therefore, β-decay radioisotopes can be used for NMR spectroscopy in material sciences. Nuclei, whose spin is zero, such as 12C and 16O, cannot be used in conventional NMR. However, nonzero-spin radioactive isotopes of carbon and oxygen can be used in β-NMR. This advantage is powerful for investigating organic materials that cannot be investigated using conventional NMR. A technique is being developed to extend β-NMR for imaging use in magnetic resonance imaging (MRI). In this study, the imaging function was realized by installing β-ray tracking detectors in a β-NMR device. Nuclear-spin-polarized radioisotopes were injected into a sample, and β-rays were emitted from their positions. Consequently, one could track back β-ray source positions on the sample. These detectors were installed into a dipole magnet to observe the magnetic resonances. A radio frequency coil was installed surrounding the sample. By combining information about the β-ray tracks and magnetic resonances, it was possible to obtain NMR spectra and images. This method is called “β-MRI.” The system was evaluated, and its performances were estimated.

A new experimental method to measure muon polarization using a scintillating material has been proposed. One of the key issues for this measurement is the choice of scintillation materials which can maintain the μ+ spin polarization for several μ+ lifetimes. Thus far, a CeF3 scintillating crystal has been known to be only a possible candidate and it is highly preferable to find other scintillators whose performance is nearly equivalent to CeF3. The residual μ+ polarization in a 2% cerium-doped LaF3 scintillating crystal was measured at the J-PARC Material and Life Science Facility (MLF) by applying the longitudinal field (LF) to the LaF3 material. The polarization was obtained to be 83 and 87 % with LF = 100 and 140 Gauss, respectively, which is high enough to measure the μ+ polarization in various experiments.

β -detected nuclear magnetic resonance ( β -NMR) is a powerful research tool in nuclear physics and material sciences. In this study, we integrated an imaging function into a β -NMR instrument. Specifically, we installed position-sensitive detectors to create a magnetic resonance imaging device, which we have named the β -MRI. We conducted experiments to evaluate the performance of this device by irradiating spin-polarized ^12 B beams on a sample, and successfully generated its material mapping image.

Charge-changing cross sections $\sigma_\mathrm{CC}$ for $^{42\textrm{--}51}$Ca on a carbon target at around 280~MeV/nucleon have been measured. The measured $\sigma_\mathrm{CC}$ values differ significantly from the previously developed calculations based on the Glauber model. However, through introduction of the charged-particle evaporation effect induced by the neutron-removal reaction in addition to the Glauber-model calculation, experimental $\sigma_\mathrm{CC}$ values on $^{12}$C at around 300~MeV/nucleon for nuclides from C to Fe isotopes are all reproduced with approximately 1\% accuracy. This proposed model systematically reproduces $\sigma_\mathrm{CC}$ data without phenomenological corrections, and can also explain experimental $\sigma_\mathrm{CC}$ values obtained in other energy regions.

A new experimental method to search for T-violating transverse muon polarization (PT) in the K+→π0μ+ν (Kμ3) decay using a segmented CeF3 calorimeter has been proposed. One of the key issues for this experiment is the choice of a scintillation material which can maintain the μ+ spin polarization for several μ+ lifetimes. The residual μ+ polarization in a CeF3 scintillating crystal was previously measured at the J-PARC Material and Life Science Facility (MLF). Unfortunately, due to the small size of the CeF3 material, beam backgrounds contributed significantly to the μSR spectra, and the absolute μ+ polarization could not be determined accurately. In order to solve this problem, a new experiment was performed at the MLF using a large CeF3 crystal, which successfully reduced the beam backgrounds to a negligible level. The residual μ+ polarization in CeF3 was measured by changing the strength of the applied longitudinal field (LF). The polarization was obtained to be 90 ± 2% with LF = 140 Gauss, which is high enough to perform the new T-violation experiment.

It is well known that the enhancement of halo neutron removal cross sections in neutron halo nuclei. This is one of the evidence for the neutron halo structure. Because the valence neutron of the isomeric state in $$^{16}$$ N is considered to be mainly occupying in the s-orbital, we studied the nuclear structure of $$^{16}$$ N as a candidate for neutron halo nucleus. In this study, we measured one-neutron removal cross sections $$\sigma _{-1n}$$ using secondary beams of $$^{16}$$ N with a mixture of ground and isomeric states. We used two types of primary beams, $$^{15}$$ N and $$^{18}$$ O, to produce $$^{16}$$ N beams with different isomeric ratios (8.7, 24.2a $$^{16}$$ N beam with a large isomeric ratio is large compared to that obtained with another beam with a small isomeric state. This result suggests that the $$^{16}$$ N isomeric state is considered to have a neutron-halo-like structure.