Exposure to ionizing radiation originates primarily from terrestrial and cosmic radiation sources. Cosmic-radiation exposure depends strongly on altitude and is additionally influenced by latitude and solar activity. Particular attention should be paid to aircraft passengers and aircrew, who may receive elevated radiation doses due to prolonged exposure at flight altitudes. In this study, Monte Carlo simulations were performed using the Geant4 toolkit (version 11.3) to investigate secondary cosmic-ray particles, including muons, neutrons, protons, electrons/positrons, and gamma photons, at altitudes of 0 m, 2100 m, and 11,300 m and latitudes of 0°, 30°, 45°, 60°, and 90°. Deposited energies in a water phantom representing the human body were used to calculate equivalent dose rates and estimate annual effective doses. The average equivalent dose rates were 0.036, 0.22, and 6.9 μSv·h−1 at 0 m, 2100 m, and 11,300 m, respectively. Dose rates showed a pronounced latitude dependence, increasing from low latitudes and reaching maximum values at 60°, followed by a decrease at 90°, consistent with the reported latitude effect of cosmic radiation. The annual effective dose for the general population at sea level ranged from 0.28 to 0.35 mSv, with an average of 0.31 mSv. For annual flight times of 10, 50, and 100 h, passenger doses were 0.069, 0.34, and 0.69 mSv, respectively, remaining below 1 mSv. For aircrew, annual doses were 3.44, 4.82, and 6.19 mSv for 500, 700, and 900 flight hours, respectively, remaining below 20 mSv. The results are consistent with literature data and demonstrate the applicability of Monte Carlo simulations for cosmic-radiation exposure assessment.
The quasielastic neutron scattering technique is an indispensable tool for probing microscopic dynamics in condensed matter at the nanoscale. However, the lack of a high-resolution spectrometer has restricted comprehensive studies of dynamics in China. To address this gap, a new time-of-flight neutron backscattering spectrometer, NuBS, is currently under construction at the China Spallation Neutron Source. This review systematically introduces basic principles, instrumental design, and scientific opportunities of NuBS. NuBS is engineered to deliver high energy resolution with a broad dynamic range, based on the moderator pulse structure. Given the wide time window of NuBS, we highlight its research prospects in frontier areas, including energy storage materials and heterogeneous catalysis. NuBS is expected to provide new opportunities for studies of complex molecular dynamics and in situ investigations, significantly elevating the capabilities of the quasielastic neutron scattering community upon its scheduled completion.
In recent years, an increasing number of national major projects have focused on the physicochemical properties of materials and the structural integrity of components in cryogenic environments. In situ neutron non-destructive testing offers a distinct advantage for scientific research conducted under cryogenic conditions. With the progressive advancement of neutron sources and neutron diffraction techniques, neutron probes have become indispensable for the in situ observation of lattice strain, phase transformation behavior, and residual stresses in materials at cryogenic temperatures. Based on the energy-resolved neutron imaging instrument (ERNI) at Beamline 13 of the China Spallation Neutron Source (CSNS), we have developed a cryogenic loading frame for in situ neutron diffraction tensile tests. This paper presents a detailed description of the mechanical structural design, cooling and control system, strength and thermal analyses, and experimental validation of the device. The apparatus enables in situ neutron diffraction experiments over a wide temperature range of 6–473 K, with an axial loading capacity of 50 kN. Furthermore, the device was employed to conduct in situ neutron diffraction measurements on austenitic 304 stainless steel at both room and cryogenic temperatures. The experimental results confirm that this equipment exhibits stable loading capability and precise temperature control, ensuring the reliability of the experimental data.
Linear dichroism (LD) optical absorption spectroscopy historically has found substantial yet still limited application in broad areas of science. In particular, full-dipole-tensor reconstruction has been onerous, usually requiring tedious and difficult measurements on single crystals at many orientations using a four-circle goniometer. As a consequence, it is very seldom done. Here, we propose, and test by numerical simulation, a simpler, faster, novel method of determining the full dipole optical absorption tensor of homogeneous planar films in real time as a function of energy (or wavelength), while requiring only minimal additional time and instrumentation. The goal of this paper is to explain the theory and to demonstrate the effectiveness and stability of the procedure using synthetic data sets. Experimental implementation and testing is deferred to future work and publications. The full-tensor spectrum, after construction from the experimental data, allows one to instantly calculate the absorption for any selected polarization direction, even those that are physically inaccessible to experimental measurement. Although our specific application in this paper is X-ray Absorption Fine Structure (XAFS) Spectroscopy, the method should be applicable to UV–Vis, IR, THz, microwave, and other wavelengths. A strength of this measurement modality is that full-tensor data can be acquired using essentially the same sort of scanning geometry that is normally used for XAFS, with only a discrete shift in the spin axis orientation between groups of scans. The additional instrumentation needed to determine the five Fourier components of the signal at each energy is minimal; two angles gives ten parameters, while six are strictly needed. Robust inversion from data to tensor elements is demonstrated, implemented via simple matrix multiplication. Outside of XAFS, FTMAPS is also expected to be applicable to diverse scientific and technological areas such as oriented bio-molecular films, semiconductor and materials physics, and process control of thin-film photovoltaics and semiconductors.
Laser Raman spectroscopy is a versatile and well-known technique to probe molecular vibrations. The aim of the study is to design and construct a compact, easy-to-use Raman spectrometer and verify its operation. A laser Raman spectrometer was constructed using a blue diode laser module operating at 402 nm, a novel and efficient combination of backscattering and sidescattering collection geometries, and a spectrometer employing an uncooled CCD (charge-coupled device). The choice of the excitation laser wavelength at 402 nm significantly improves the Raman generation efficiency compared to that for excitation lasers operating at longer wavelengths. Off-the-shelf optical components were used throughout the system. The Raman spectrometer is relatively compact and easy to operate. The operation of the Raman spectrometer was verified with well-known molecules. Raman spectra of several sample materials (both liquids and solids) were acquired and presented.
