Nuclear Science and Techniques最新文献

The hard X-ray nanoprobe beamline BL13U is a phase-II beamline project at the Shanghai Synchrotron Radiation Facility. The beamline aims to enable comprehensive experiments at high spatial resolutions ranging from 50 to 10 nm. The X-ray energy range of the beamline, 5–25 keV, can detect most elements in the periodic table. Two operating modes were designed to accommodate the experimental requirements of high-energy resolution or high photon flux, respectively. X-ray nanofluorescence, nanodiffraction, and coherent diffraction imaging are developed as the main experimental techniques for BL13U. This paper describes the beamline optics, end station configurations, experimental methods under development, and preliminary test results. This comprehensive overview aims to provide a clear understanding of the beamline capabilities and potential applications.

Cone-beam computed tomography (CBCT) is mostly used for position verification during the treatment process. However, severe image artifacts in CBCT hinder its direct use in dose calculation and adaptive radiation therapy re-planning for proton therapy. In this study, an improved U-Net neural network named CBAM-U-Net was proposed for CBCT noise reduction in proton therapy, which is a CBCT denoised U-Net network with convolutional block attention modules. The datasets contained 20 groups of head and neck images. The CT images were registered to CBCT images as ground truth. The original CBCT denoised U-Net network, sCTU-Net, was trained for model performance comparison. The synthetic CT(SCT) images generated by CBAM-U-Net and the original sCTU-Net are called CBAM-SCT and U-Net-SCT images, respectively. The HU accuracies of the CT, CBCT, and SCT images were compared using four metrics: mean absolute error (MAE), root mean square error (RMSE), peak signal-to-noise ratio (PSNR), and structure similarity index measure (SSIM). The mean values of the MAE, RMSE, PSNR, and SSIM of CBAM-SCT images were 23.80 HU, 64.63 HU, 52.27 dB, and 0.9919, respectively, which were superior to those of the U-Net-SCT images. To evaluate dosimetric accuracy, the range accuracy was compared for a single-energy proton beam. The (gamma)-index pass rates of a 4 cm (times) 4 cm scanned field and simple plan were calculated to compare the effects of the noise reduction capabilities of the original U-Net and CBAM-U-Net on the dose calculation results. CBAM-U-Net reduced noise more effectively than sCTU-Net, particularly in high-density tissues. We proposed a CBAM-U-Net model for CBCT noise reduction in proton therapy. Owing to the excellent noise reduction capabilities of CBAM-U-Net, the proposed model provided relatively explicit information regarding patient tissues. Moreover, it maybe be used in dose calculation and adaptive treatment planning in the future.

The aim of this study is to evaluate the uncertainty of (2pi alpha ) and (2pi beta ) surface emission rates using the windowless multiwire proportional counter method. This study used the Monte Carlo method (MCM) to validate the conventional Guide to the Expression of Uncertainty in Measurement (GUM) method. A dead time measurement model for the two-source method was established based on the characteristics of a single-channel measurement system, and the voltage threshold correction factor measurement function was indirectly obtained by fitting the threshold correction curve. The uncertainty in the surface emission rate was calculated using the GUM method and the law of propagation of uncertainty. The MCM provided clear definitions for each input quantity and its uncertainty distribution, and the simulation training was realized with a complete and complex mathematical model. The results of the surface emission rate uncertainty evaluation for four radioactive plane sources using both methods showed the uncertainty’s consistency (E_text {n} < 0.070) for the comparison of each source, and the uncertainty results of the GUM were all lower than those of the MCM. However, the MCM has a more objective evaluation process and can serve as a validation tool for GUM results.

A Laue microdiffraction beamline (BL03HB) was constructed at the Shanghai Synchrotron Radiation Facility (SSRF). This beamline features two consecutive focusing points in two different sectors within its end station, the first dedicated to protein crystallography and the other tailored to materials science applications. Based on a superbend dipole magnet with a magnetic field of 2.29 T, a two-stage focusing design was implemented with two sets of Kirkpatrick-Baez mirrors to achieve a micro white beam as small as 4.2 ({upmu })m (times)4.3 ({upmu })m at the first sector and 0.9 ({upmu })m (times)1.3 ({upmu })m at the second sector in the standard beamline operation mode at SSRF. The X-ray microbeam in the two sectors can be easily switched between monochromatic and white beams by moving a four-bounce monochromator in or out of the light path, respectively. In the protein crystallography sector, white-beam Laue microdiffraction was demonstrated to successfully determine the structure of protein crystals from only a few images of diffraction data collected by a Pilatus 2 M area detector. In the materials science sector, the white-beam Laue diffraction was collected in a reflection geometry using another Pilatus 2 M area detector, which could map the microstructural distribution on the sample surface by scanning the samples. In general, the BL03HB beamline promotes the application of Laue microdiffraction in both protein crystallography and materials science. This paper presents a comprehensive overview of the BL03HB beamline, end station, and the first commission results.

In nuclear collisions at RHIC energies, an excess of (Omega) hyperons over (bar{Omega }) is observed, indicating that (Omega) has a net baryon number despite s and (bar{s}) quarks being produced in pairs. The baryon number in (Omega) may have been transported from the incident nuclei and/or produced in the baryon-pair production of (Omega) with other types of anti-hyperons such as (bar{Xi }). To investigate these two scenarios, we propose to measure the correlations between (Omega) and K and between (Omega) and anti-hyperons. We use two versions, the default and string-melting, of a multiphase transport (AMPT) model to illustrate the method for measuring the correlation and to demonstrate the general shape of the correlation. We present the (Omega)-hadron correlations from simulated Au+Au collisions at (sqrt{s_text{NN}} = 7.7) and (14.6 textrm{GeV}) and discuss the dependence on the collision energy and on the hadronization scheme in these two AMPT versions. These correlations can be used to explore the mechanism of baryon number transport and the effects of baryon number and strangeness conservation on nuclear collisions.

BL02U2 of the Shanghai Synchrotron Radiation Facility is a surface diffraction beamline with a photon flux of 5.5 × 10¹² photons/s at 10 keV and a beam size of 160 µm × 80 µm at the sample site. It is dedicated to studying surfaces (solid–vacuum, solid–gas) and interfaces (solid–solid, solid–liquid, and liquid–liquid) in nanoscience, condensed matter, and soft matter systems using various surface scattering techniques over an energy range of 4.8–28 keV with transmission and reflection modes. Moreover, BL02U2 has a high energy resolution, high angular resolution, and low beam divergence, which can provide excellent properties for X-ray diffraction experiments, such as grazing incident X-ray diffraction, X-ray reflectivity, crystal truncation rods, and liquid X-ray scattering. Diversity of in situ environments can also be provided for the samples studied. This paper describes the setup of the new beamline and its applications in various fields.

This paper details the development and testing of the first working prototype of the S-band high-power klystron, accomplished at the Budker Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences (BINP SB RAS). Upon testing, the klystron demonstrated the following parameters: an operating frequency of 2856 MHz and a peak power output of 50 MW. The paper presents the klystron's design, its constituent units, and pertinent processing procedures, along with discussions on the measurement of its parameters.

Small-scale measurements of the radon exhalation rate using the flow-through and closed-loop methods were conducted on the surface of a uranium tailing pond to better understand the differences between the two methods. An abnormal radon exhalation behavior was observed, leading to computational fluid dynamics (CFD)-based simulations in which dynamic radon migration in a porous medium and accumulation chamber was considered. Based on the in-situ experimental and numerical simulation results, variations in the radon exhalation rate subject to permeability, flow rate, and insertion depth were quantified and analyzed. The in-situ radon exhalation rates measured using the flow-through method were higher than those measured using the closed-loop method, which could be explained by the negative pressure difference between the inside and outside of the chamber during the measurements. The consistency of the variations in the radon exhalation rate between the experiments and simulations suggests the reliability of CFD-based techniques in obtaining the dynamic evolution of transient radon exhalation rates for diffusion and convection at the porous medium-air interface. The synergistic effects of the three factors (insertion depth, flow rate, and permeability) on the negative pressure difference and measured exhalation rate were quantified, and multivariate regression models were established, with positive correlations in most cases; the exhalation rate decreased with increasing insertion depth at a permeability of 1 × 10⁻¹¹ m². CFD-based simulations can provide theoretical guidance for improving the flow-through method and thus achieve accurate measurements.