Quantum Beam Sci., Volume 8, Issue 1 (March 2024) – 9 articles

The advance of laser-driven neutron sources (LDNSs) has enabled neutron resonance spectroscopy to be performed with a single shot of a laser. In this study, we describe a detection system of epithermal (∼eV) neutrons especially designed for neutron resonance spectroscopy. A time-gated photomultiplier tube (PMT) with a high cut-off ratio was introduced for epithermal neutron detection in a high-power laser experiment at the Institute of Laser Engineering, Osaka University. We successfully reduced the PMT response to the intense hard X-ray generated as a result of the interaction between laser light and the target material. A time-gated circuit was designed to turn off the response of the PMT during the laser pulse and resume recording the signal when neutrons arrive. The time-gated PMT was coupled with a ⁶Li glass scintillator, serving as a time-of-flight (TOF) detector to measure the neutron resonance absorption values of ¹⁸²W and ¹⁰⁹Ag in a laser-driven epithermal neutron generation experiment. The neutron resonance peaks at $4.15$ eV of ¹⁸²W and $5.19$ eV of ¹⁰⁹Ag were detected after a single pulse of laser at a distance of 1.07 m. Full article

FOCUS is a direct-geometry cold neutron time-of-flight spectrometer at SINQ (PSI, CH). Its neutron guide was exchanged in 2019/2020 within the SINQ Upgrade project, while the rest of the instrument remained unchanged. The new guide provided a significant intensity increase across the whole spectrum, especially at short wavelengths, due to the more efficient transport and extended phase space of the transported neutrons. The practically available energy transfer range (at the neutron energy loss side) was increased to about 40 meV. The main reason for the intensity benefit at short incident wavelengths was the improved guide coating, whereas at long wavelengths it was the new ballistic shape. The interesting part of the guide is the “peanut shape” of the curved part in the horizontal plane. For this, we derived the analytical restriction on the geometry to avoid a direct line of sight from the source. The guide geometry and the supermirror coating were optimized using Mcoptimize, a particle swarm optimization routine employing Mcstas. Future ballistic neutron guides may profit from the presented approaches, optimization strategy, and results. Full article

Comprehensive information on in situ microstructural and crystallographic changes during the preparation/manufacturing processes of various materials is highly necessary to precisely control the microstructural morphology and the preferred orientation (or texture) characteristics for achieving an excellent strength–ductility–toughness balance in advanced engineering materials. In this study, in situ isothermal annealing experiments with cold-rolled 17Ni-0.2C (mass%) martensitic steel sheets were carried out by using the TAKUMI and ENGIN-X time-of-flight neutron diffractometers. The inverse pole figures based on full-profile refinement were extracted to roughly evaluate the preferred orientation features along three principal sample directions of the investigated steel sheets, using the General Structure Analysis System (GSAS) software with built-in generalized spherical harmonic functions. The consistent rolling direction (RD) inverse pole figures from TAKUMI and ENGIN-X confirmed that the time-of-flight neutron diffraction has high repeatability and statistical reliability, revealing that the principal preferred orientation evaluation of steel materials can be realized through 90° TD ➜ ND (transverse direction ➜ normal direction) rotation of the investigated specimen on the sample stage during two neutron diffraction experiments. Moreover, these RD, TD, and ND inverse pole figures before and after the in situ experiments were compared with the corresponding inverse pole figures recalculated from the MUSASI-L complete pole figure measurement and the HIPPO in situ microstructure evaluation, respectively. The similar orientation distribution characteristics suggested that the principal preferred orientation evaluation method can be applied to the in situ microstructural evolution of bulk orthorhombic materials and spatially resolved principal preferred orientation mappings of large engineering structure parts. Full article

The high-intensity and monochromatic radiation sources in the water window spectral range are desirable for many applications. One of the potential candidates of soft X-ray sources is polarization radiation produced by a charged particle passing through a thin foil. In the soft X-ray range near the absorption edges of a target material, the real part of dielectric permittivity can exceed unity, and the Tamm–Frank criterion is fulfilled. Thus, two types of radiation are produced: transition and Cherenkov radiation. In this report, we theoretically investigated the spectral characteristics of radiation produced in both cases when the Tamm–Frank criterion is met or not met. We showed the dependences of the spectrum as a function of thickness and the incidence angle. To describe the properties of polarization radiation and the complex dielectric permittivity, the polarization current approach and Henke’s model were used, respectively. Full article

An experimental platform for laser-driven ion (sub-MeV) acceleration and potential applications was commissioned at the HiLASE laser facility. The auxiliary beam of the Bivoj laser system operating at a GW level peak power (~10 J in 5–10 ns) and 1–10 Hz repetition rate enabled a stable production of high-current ion beams of multiple species (Al, Ti, Fe, Si, Cu, and Sn). The produced laser–plasma ion sources were fully characterized against the laser intensity on the target (10¹³–10¹⁵ W/cm²) by varying the laser energy, focal spot size, and pulse duration. The versatility and tuneability of such high-repetition-rate laser–plasma ion sources are of potential interest for user applications. Such a statistically accurate study was facilitated by the large amount of data acquired at the high repetition rate (1–10 Hz) provided by the Bivoj laser system. Full article

Small-scale facilities play a significant role in the landscape of nuclear physics research in Europe. They address a wide range of fundamental questions and are essential for teaching and training personnel in accelerator technology and science, providing them with diverse skill sets, complementary to large projects. The current status and perspectives of nuclear physics research at small-scale facilities in Europe will be given. Full article

The magnetron injection gun (MIG) is an essential component of the gyrotron traveling wave tube (gyro-TWT). Although the electron beam status influences the performance of the device, it cannot be measured directly in the experiment. An online evaluation module (OEM) for the experiment is developed to calculate the instant beam parameters of MIG. The OEM, by reconstructing the geometry of the MIG and related magnetic field distribution, can obtain the electron beam status under the operating parameters through the online simulation. The beam velocity spread of thermal emission with instant temperature and surface roughness are also considered. The validation is done in a W-band gyro-TWT, and the beam performance is evaluated in the experiment. With a pitch factor of 1.06 electron beam, the velocity spread affected by the electric-magnetic mismatch, thermal emission, and roughness is 1.00%, 0.56%, and 0.43%, respectively. The other beam parameters are also presented in the developed module. The OEM could guide and accelerate the testing process and ensure the safe and stable operation of the device. Full article

A sample of 18 double-relief coins from different poleis of Magna Graecia and ancient Italy has been analysed using a handheld XRF spectrometer directly inside the Museo Provinciale Campano (Capua, Italy). The data analysis shows that (i) the main elements are Ag and Cu, indicating that the coins are of high fineness (average Ag 95.7%), (ii) trace elements can help to characterise the coins, (iii) a superficial chemically altered layer (corrosion) is absent, (iv) the values of ratio Ag Kα/Lα evidence the presence of an enrichment layer on the surface of silver or subaerata in some coins. Multivariate statistical analysis and graph analysis allowed the coins to be assigned to different groups with the highest possible accuracy on the basis of the chemical data obtained and models to be constructed to classify the coins according to their historical periods. Full article

Probabilistic fracture mechanics (PFM) is increasingly recognized as a viable approach for evaluating the structural integrity of nuclear components, such as piping, primarily affected by stress corrosion cracking (SCC). PFM analysis requires several input parameters, among which welding residual stress is critically important due to its significant influence on SCC initiation and propagation. Recently, a novel technique involving a double-exposure method (DEM) utilizing synchrotron X-rays was introduced as an effective means for measuring welding residual stress with high spatial resolution. In this paper, we applied DEM to assess the residual stress of a plate specimen, which was extracted from a welded pipe through electrical discharge machining. Consequently, detailed stress maps under a plane stress state were generated. Additionally, the residual stress distributions in the welded pipe under a triaxial stress state were evaluated using neutron diffraction. Based on these findings, we proposed a methodology to acquire detailed stress maps of welded pipes by combining high-energy synchrotron X-rays and neutron diffraction. Full article