Nuclear Science and Techniques最新文献

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.

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.

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.

We present a theoretical study of the medium modifications of the (p_textrm{T}) balance ((x_textrm{J})) of dijets in Xe+Xe collisions at (sqrt{s_textrm{NN}}=5.44) TeV. The initial production of dijets was carried out using the POWHEG+PYTHIA8 prescription, which matches the next-to-leading-order (NLO) QCD matrix elements with the parton shower (PS) effect. The SHELL model described the in-medium evolution of nucleus–nucleus collisions using a transport approach. The theoretical results of the dijet (x_textrm{J}) in the Xe+Xe collisions exhibit more imbalanced distributions than those in the p+p collisions, consistent with recently reported ATLAS data. By utilizing the Interleaved Flavor Neutralisation, an infrared-and-collinear-safe jet flavor algorithm, to identify the flavor of the reconstructed jets, we classify dijets processes into three categories: gluon–gluon (gg), quark–gluon (qg), and quark–quark (qq), and investigated the respective medium modification patterns and fraction changes of the gg, qg, and qq components of the dijet sample in Xe+Xe collisions. It is shown that the increased fraction of qg component at a small (x_textrm{J}) contributes to the imbalance of the dijet; in particular, the (q_1g_2) (quark-jet-leading) dijets experience more significant asymmetric energy loss than the (g_1q_2) (gluon-jet-leading) dijets traversing the QGP. By comparing the (Delta langle x_textrm{J}rangle = langle x_textrm{J} rangle _textrm{pp} - langle x_textrm{J} rangle _textrm{AA}) of inclusive, (cbar{c}) and (bbar{b}) dijets in Xe+Xe collisions, we observe (Delta langle x_textrm{J} rangle _mathrm{incl.}>Delta langle x_textrm{J} rangle _mathrm{cbar{c}}>Delta langle x_textrm{J} rangle _mathrm{bbar{b}}). Moreover, (rho _textrm{Xe, Pb}), the ratios of the nuclear modification factors of dijets in Xe+Xe to those in Pb+Pb, were calculated, which indicates that the yield suppression of dijets in Pb+Pb is more pronounced than that in Xe+Xe owing to the larger radius of the lead nucleus.

The advantages of a flat-panel X-ray source (FPXS) make it a promising candidate for imaging applications. Accurate imaging-system modeling and projection simulation are critical for analyzing imaging performance and resolving overlapping projection issues in FPXS. The conventional analytical ray-tracing approach is limited by the number of patterns and is not applicable to FPXS-projection calculations. However, the computation time of Monte Carlo (MC) simulation is independent of the size of the patterned arrays in FPXS. This study proposes two high-efficiency MC projection simulators for FPXS: a graphics processing unit (GPU)-based phase-space sampling MC (gPSMC) simulator and GPU-based fluence sampling MC (gFSMC) simulator. The two simulators comprise three components: imaging-system modeling, photon initialization, and physical-interaction simulations in the phantom. Imaging-system modeling was performed by modeling the FPXS, imaging geometry, and detector. The gPSMC simulator samples the initial photons from the phase space, whereas the gFSMC simulator performs photon initialization from the calculated energy spectrum and fluence map. The entire process of photon interaction with the geometry and arrival at the detector was simulated in parallel using multiple GPU kernels, and projections based on the two simulators were calculated. The accuracies of the two simulators were evaluated by comparing them with the conventional analytical ray-tracing approach and acquired projections, and the efficiencies were evaluated by comparing the computation time. The results of simulated and realistic experiments illustrate the accuracy and efficiency of the proposed gPSMC and gFSMC simulators in the projection calculation of various phantoms.

The Shanghai Laser Electron Gamma Source (SLEGS, located in BL03SSID) beamline at the Shanghai Synchrotron Radiation Facility (SSRF) is a Laser Compton Scattering (LCS) gamma source used for the investigation of nuclear structure, which is in extensive demand in fields such as nuclear astrophysics, nuclear cluster structure, polarization physics, and nuclear energy. The beamline is based on the inverse Compton scattering of 10640 nm photons on 3.5 GeV electrons and a gamma source with variable energy by changing the scattering angle from 20(^circ) to 160(^circ). (gamma) rays of 0.25(-)21.1 MeV can be extracted by the scheme consisting of the interaction chamber, coarse collimator, fine collimator, and attenuator. The maximum photon flux for 180(^circ) is approximately (10^{7}) photons/s at the target at 21.7 MeV, with a 3-mm-diameter beam. The beamline was equipped with four types of spectrometers for experiments in ((gamma),(gamma)’), ((gamma),n), ((gamma),p), and ((gamma,!alpha)). At present, Nuclear Resonance Fluorescence (NRF) spectrometry, Flat-Efficiency neutron Detector (FED) spectrometry, neutron Time-Of-Flight (TOF) spectrometry, and Light-Charged Particle (LCP) spectrometry methods have been developed.