Quantum Beam Sci., Volume 4, Issue 4 (December 2020) – 13 articles

Lasers can be used to bend 2D metal sheets into complex 3D objects in a process called ‘laser forming.’ Laser forming bends metal sheets by locally heating the sheets to generate plastic strains and is an established metal bending technology in the shipbuilding industry. Recent studies have investigated the laser forming of thin metal parts as a complementary rapid prototyping technology to metal 3D printing. This review discusses the laser forming process, beginning with the mechanisms before covering various design considerations. Laser forming for the rapid manufacturing of metal parts is then reviewed, including the recent advances in process planning, before highlighting promising future research directions. Full article

Amorphizable ceramics (LiNbO₃, ZrSiO₄, and Gd₃Ga₅O₁₂) were irradiated with 200 MeV Au ions at an oblique incidence angle, and the as-irradiated samples were observed by transmission electron microscopy (TEM). Ion tracks in amorphizable ceramics are confirmed to be homogenous along the ion paths. Magnified TEM images show the formation of bell-shaped hillocks. The ion track diameter and hillock diameter are similar for all the amorphizable ceramics, while there is a tendency for the hillocks to be slightly bigger than the ion tracks. For SrTiO₃ (STO) and 0.5 wt% niobium-doped STO (Nb-STO), whose hillock formation has not been fully explored, 200 MeV Au ion irradiation and TEM observation were also performed. The ion track diameters in these materials are found to be markedly smaller than the hillock diameters. The ion tracks in these materials exhibit inhomogeneity, which is similar to that reported for non-amorphizable ceramics. On the other hand, the hillocks appear to be amorphous, and the amorphous feature is in contrast to the crystalline feature of hillocks observed in non-amorphizable ceramics. No marked difference is recognized between the nanostructures in STO and those in Nb-STO. The material dependence of the nanostructure formation is explained in terms of the intricate recrystallization process. Full article

A method of time-of-flight, small-angle neutron scattering (TOF-SANS) has been developed based on the iMATERIA powder diffractometer at BL20, of the Materials and Life Sciences Facility (MLF) at the high-intensity proton accelerator (J-PARC). A large-area detector for SANS, which is composed of triple-layered ³He tube detectors, has a hole at its center in order to release a direct beam behind and to detect ultra-small-angle scattering. As a result, the pulsed-neutron TOF method enables us to perform multiscale observations covering 0.003 < q (Å⁻¹) < 40 (q_max/q_mix = 1.3 × 10⁴) and to determine the static structure factor S(q) and/or form factor P(q) under real-time and in-situ conditions. Our challenge, using unique sample accessories of a super-conducting magnet and polarized neutron, is dynamic nuclear polarization (DNP) for contrast variation, especially for industrial use. To reinforce conventional SANS measurements with powder materials, grazing-incidence small-angle neutron scattering (GISANS) or reflectivity is also available on the iMATERIA instrument. Full article

This article introduces software called Phonon Explorer that implements a data mining workflow for large datasets of the neutron scattering function, S(Q, ω), measured on time-of-flight neutron spectrometers. This systematic approach takes advantage of all useful data contained in the dataset. It includes finding Brillouin zones where specific phonons have the highest scattering intensity, background subtraction, combining statistics in multiple Brillouin zones, and separating closely spaced phonon peaks. Using the software reduces the time needed to determine phonon dispersions, linewidths, and eigenvectors by more than an order of magnitude. Full article

The time-of-flight elastic recoil detection analysis (TOF-ERDA) method is one of the ion beam analysis methods that is capable of analyzing light elements in a sample with excellent depth resolution. In this method, simultaneous measurements of recoil ion energy and time of flight are performed, and ion mass is evaluated. The energy of recoil ions is calculated from TOF, which gives better energy resolution than conventional Silicon semiconductor detectors (SSDs). TOF-ERDA is expected to be particularly applicable for the analysis of light elements in thin films. In this review, the principle of TOF-ERDA measurement and details of the measurement equipment along with the performance of the instrumentation, including depth resolution and measurement sensitivity, are described. Examples of TOF-ERDA analysis are presented with a focus on the results obtained from the measurement system developed by the author. Full article

Evolution of depth profiles of the refractive index in Y₃Al₅O₁₂ (YAG) crystals were studied under 200 MeV ¹³⁶Xe¹⁴⁺ ion irradiation, since the index can be related with the stress change and/or the defect formation by the irradiation. Using the prism-coupling and the end-surface coupling methods, various waveguide (WG) modes were detected. Then, the index depth profiles were determined by reproducing the observed WG modes. The index changes were observed at three different depth regions; (i) a sharp dip at 13 μm in depth, which is attributed to the nuclear stopping S_n peak, (ii) a plateau near the surface between 0 and 3 μm in depth, which can be ascribed to the electronic stopping S_e, since S_e has a very broad peak at the surface, and (iii) a broad peak at 6 μm in depth. Since the last peak is ascribed to neither of S_e nor S_n peak, it could be attributed to the synergy effect of S_e and S_n. Full article

The cell inactivation and DNA double-strand break (DSB) induction by K-shell ionization of phosphorus atoms and Auger electrons were investigated. Monochromatic X-rays of on and below the phosphorus K-shell absorption peak, 2.153 keV and 2.147 keV were exposed to Chinese hamster lung fibroblast V79 cells. Survival fractions were plotted against exposure, Ψ [nC/kg] and the linear-quadratic model was adapted to estimate the parameters, α and β, of the survival curves. DSB induction rate [DSB/cell/Ψ] was estimated from the measured fractions of induced DNA fragments below 4.6 Mbp (F_ind(k < 4.6)), which were determined using pulse field gel electrophoresis. As results, cell inactivation and DSB induction rate of on the peak were significantly higher compared to that of the below. However, when converting Ψ to absorbed dose (Gy) of cell nucleus, the enhanced effect was only observed for parameter α, and not for a survival dose (Gy) of 37%, 10%, and 1% nor for a DSB induction rate. Our findings indicate that enhancement of cell inactivation and DSB induction were due to the additional dose delivered to the DNA and more complex DSB lesions were induced due to the release of phosphorus K-shell photoelectrons and Auger electrons. Full article

The TERESA (TEstbed for high REpetition-rate Sources of Accelerated particles) target area, recently commissioned with the L3-HAPLS laser at Extreme Light Infrastructure (ELI)-Beamlines, is presented. Its key technological sections (vacuum and control systems, laser parameters and laser beam transport up to the target) are described, along with an overview of the available plasma diagnostics and targetry, tested at relativistic laser intensities. Perspectives of the TERESA laser–plasma experimental area at ELI-Beamlines are briefly discussed. Full article

Multiplication and rearrangement of dislocations in face-centered cubic (FCC) metals during tensile deformation are affected by grain size, stacking fault energy (SFE), and solute elements. X-ray diffraction (XRD) line-profile analysis can evaluate the dislocation density ($\rho$) and dislocation arrangement (M) from the strength of the interaction between dislocations. However, the relationship between M and $\rho$ has not been thoroughly addressed. In this study, multiplication and rearrangement of dislocations in FCC metals during tensile deformation was evaluated by XRD line-profile analysis. Furthermore, the effects of grain size, SFE, and solute elements on the extent of dislocation rearrangement were evaluated with varying M values during tensile deformation. M decreased as the dislocation density increased. By contrast, grain size and SFE did not exhibit a significant influence on the obtained M values. The influence of solute species and concentration of solute elements on M changes were also determined. In addition, the relationship between dislocation substructures and M for tensile deformed metals were also explained. Dislocations were loosely distributed at M > 1, and cell walls gradually formed by gathering dislocations at M < 1. While cell walls became thicker with decreasing M in metals with low stacking fault energy, thin cell walls with high dislocation density formed for an M value of 0.3 in metals with high stacking fault energy. Full article

In polymer materials, residual stress introduced during injection molding affects yield reduction due to deformation during molding and delayed fracture during operation, so the establishment of nondestructive stress evaluation of polymer products is desirable. The X-ray elastic constants of polycarbonate were measured for the purpose of obtaining fundamental data for X-ray stress measurement of amorphous polymer materials. The structural function was obtained from the diffraction data, and the strain measured by X-ray was determined from the shift of the first peak by the Q-space method. The peak position was determined using the pseudo-Voigt function approximation method and the diffraction line width method. The Young’s modulus measured by X-ray obtained by the diffraction line width method was close to the mechanical value. Although these values varied widely, they changed depending on the peak ratio. A simple and practical measurement method directly using the raw profile data was also discussed. The Young’s modulus determined by the diffraction line width method decreased with increasing peak ratio. On the other hand, the values determined by the pseudo-Voigt method were almost constant, irrespective of the peak ratio. The strain calculated by the line width method was determined more accurately than that by the pseudo-Voigt method. Full article

The equation of motion for a radiating charged particle is known as the Lorentz–Abraham–Dirac (LAD) equation. The radiation reaction force in the LAD equation contains a third time-derivative term, called the Schott term, which leads to a runaway solution and a pre-acceleration solution. Since the Schott energy is the field energy confined to an area close to the particle and reversibly exchanged between particle and fields, the question of how it affects particle motion is of interest. In here we have obtained solutions for the LAD equation with and without the Schott term, and have compared them quantitatively. We have shown that the relative difference between the two solutions is quite small in the classical radiation reaction dominated regime. Full article

Recently, we have developed a novel dynamic nuclear polarization (DNP) apparatus with a magnetic field of 7 T and a sample temperature of 1 K. High proton spin polarizations from −84% to 76%, for TEMPO doped polystyrene samples, have been demonstrated. This DNP apparatus satisfies the simultaneous requirement for quick and easy sample exchange and high DNP performance. On the iMATERIA (BL20) instrument at J-PARC, the first beam experiment using this DNP apparatus has been performed. For this experiment, the beamline was equipped with a supermirror polarizer. The stray magnetic field due to the superconducting magnet for DNP was also evaluated. The stray magnetic field plays an important role for in maintaining the neutron polarization during the transportation from the polarizer to the sample. The small-angle neutron scattering (SANS) profiles of silica-filled rubber under dynamically polarized conditions are presented. By applying our new analytical approach for SANS coherent scattering intensity, neutron polarization (P_N) as a function of neutron wavelength was determined. Consequently, for the neutron wavelength, range from 4 Å to 10 Å, |P_N| was sufficient for DNP-SANS studies. Full article

An area detector with a central hole structure was built up for small-angle neutron scattering (SANS) on the iMATERIA instrument at Japan Proton Accelerator Research Complex (J-PARC). Linear position-sensitive detector tubes filled with ³He gas were arranged in three layers leaving a central hole. As a result of the calibration process, a SANS measurement with wide q-range from 0.007 Å⁻¹ to 4.3 Å⁻¹ was achieved in double-frame operation, supplying neutrons with wavelengths from 1 Å to 10 Å. As a merit of this central hole structure, neutron transmission can be measured simultaneously to reduce experimental time and effort. This is ideal for time-resolved studies, in which the sample transmission can be time-dependent, throughout the whole experiment. Additionally, the data storage system in ‘event mode’ format provides an excellent platform for such time-resolved experiments. Full article