Latest Issue
Issue 7 ， 2023
- Abstract：Plastic scintillators (PSs) embedded with wavelength-shifting fibers are widely used in high-energy particle physics, such as in muon taggers, as well as in medical physics and other applications. In this study, a simulation package was built to evaluate the effects of the diameter and layout of optical fibers on the light yield with different configurations. The optimal optical configuration was designed based on simulations and validated using two PS prototypes under certain experimental conditions. A top veto tracker (TVT) for the JUNO-TAO experiment, comprising four layers of 160 strips of PS, was designed and evaluated. The threshold was evaluated when the muon tagging efficiency of a PS strip was >99%. The efficiency of three-layer out of four-layer of TVT is >99%, even with a tagging efficiency of a single strip as low as 97%, using a threshold of 10 photoelectrons and assuming a 40% silicon PM photon detection efficiency.Keywords：Plastic scintillator;WLS fiber;Light yield;Optical transmission performance;Muon tagging efficiency;JUNO-TAO
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Published：2023-08-16 - Abstract：Accurate 3-Dimensional (3-D) reconstruction technology for non-destructive testing based on digital radiography (DR) is of great importance for alleviating the drawbacks of the existing computed tomography (CT)-based method. The commonly used Monte Carlo simulation method ensures well-performing imaging results for DR. However, for 3-D reconstruction, it is limited by its high time consumption. To solve this problem, this study proposes a parallel computing method to accelerate Monte Carlo simulation for projection images with a parallel interface and a specific DR application. The images are utilized for 3-D reconstruction of the test model. We verify the accuracy of parallel computing for DR and evaluate the performance of two parallel computing modes—multithreaded applications (G4-MT) and message-passing interfaces (G4-MPI)—by assessing parallel speedup and efficiency. This study explores the scalability of the hybrid G4-MPI and G4-MT modes. The results show that the two parallel computing modes can significantly reduce the Monte Carlo simulation time because the parallel speedup increment of Monte Carlo simulations can be considered linear growth, and the parallel efficiency is maintained at a high level. The hybrid mode has strong scalability, as the overall run time of the 180 simulations using 320 threads is 15.35 h with 10 billion particles emitted, and the parallel speedup can be up to 151.36. The 3-D reconstruction of the model is achieved based on the filtered back projection (FBP) algorithm using 180 projection images obtained with the hybrid G4-MPI and G4-MT. The quality of the reconstructed sliced images is satisfactory because the images can reflect the internal structure of the test model. This method is applied to a complex model, and the quality of the reconstructed images is evaluated.Keywords：Parallel computing;Monte Carlo;Digital radiography;3-D reconstruction
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Published：2023-08-16 - Abstract：In airborne gamma ray spectrum processing, different analysis methods, technical requirements, analysis models, and calculation methods need to be established. To meet the engineering practice requirements of airborne gamma-ray measurements and improve computational efficiency, an improved shuffled frog leaping algorithm–particle swarm optimization convolutional neural network (SFLA-PSO CNN) for large-sample quantitative analysis of airborne gamma-ray spectra is proposed herein. This method was used to train the weight of the neural network, optimize the structure of the network, delete redundant connections, and enable the neural network to acquire the capability of quantitative spectrum processing. In full-spectrum data processing, this method can perform the functions of energy spectrum peak searching and peak area calculations. After network training, the mean SNR and RMSE of the spectral lines were 31.27 and 2.75, respectively, satisfying the demand for noise reduction. To test the processing ability of the algorithm in large samples of airborne gamma spectra, this study considered the measured data from the Saihangaobi survey area as an example to conduct data spectral analysis. The results show that calculation of the single-peak area takes only 0.13~0.15 ms, and the average relative errors of the peak area in the U, Th, and K spectra are 3.11%, 9.50%, and 6.18%, indicating the high processing efficiency and accuracy of this algorithm. The performance of the model can be further improved by optimizing related parameters, but it can already meet the requirements of practical engineering measurement. This study provides a new idea for the full-spectrum processing of airborne gamma rays.Keywords：Large sample;Airborne gamma spectrum (AGS);Shuffled frog leaping algorithm (SFLA);Particle swarm optimization (PSO);Convolutional neural network (CNN)
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Published：2023-08-16
NUCLEAR ELECTRONICS AND INSTRUMENTATION
- Abstract：The Cooling Storage Ring external-target experiment (CEE) spectrometer is used to study the nuclear matter created in heavy-ion collisions at
= 2.1-2.4 GeV with the aim to reveal the quantum chromodynamics phase structure in the high-baryon density region. Collective flow is considered an effective probe for evaluating the properties of media during high-energy nuclear collisions. One of the main functions of the zero-degree calorimeter (ZDC), a subdetector system in the CEE, is to determine the reaction plane in heavy-ion collisions. This step is crucial for measuring the collective flow and other reaction-plane-related analyses. In this paper, we illustrate the procedures for event-plane determination using the ZDC. Finally, isospin-dependent quantum molecular dynamics model-based predictions of the rapidity dependence of the directed and elliptical flows for p, d, t, 3He, and 4He, produced in 2.1 GeV U+U collisions, are presented. Keywords：QCD phase structure;Heavy-ion collisions;Collective flow;Reaction plane;Zero-Degree Calorimeter- 109
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Published：2023-08-16 - Abstract：The possible exotic nuclear properties in the neutron-rich Ca, Ni, Zr, and Sn isotopes are examined with the continuum Skyrme Hartree–Fock–Bogoliubov theory in the framework of the Green's function method. The pairing correlation, the couplings with the continuum, and the blocking effects for the unpaired nucleon in odd-A nuclei are properly treated. The Skyrme interaction SLy4 is adopted for the ph channel and the density-dependent δ interaction is adopted for the pp channel, which well reproduce the experimental two-neutron separation energies S2n and one-neutron separation energies Sn. It is found that the criterion Sn>0 predicts a neutron drip line with neutron numbers much smaller than those for S2n>0. Owing to the unpaired odd neutron, the neutron pairing energies -Epair in odd-A nuclei are much lower than those in the neighboring even-even nuclei. By investigating the single-particle structures, the possible halo structures in the neutron-rich Ca, Ni, and Sn isotopes are predicted, where sharp increases in the root-mean-square (rms) radii with significant deviations from the traditional
rule and diffuse spatial density distributions are observed. Analyzing the contributions of various partial waves to the total neutron density ρlj(r)/ρ(r) reveals that the orbitals located around the Fermi surface—particularly those with small angular momenta—significantly affect the extended nuclear density and large rms radii. The number of neutrons Nλ (N0) occupying above the Fermi surface λn (continuum threshold) is discussed, whose evolution as a function of the mass number A in each isotope is consistent with that of the pairing energy, supporting the key role of the pairing correlation in halo phenomena. Keywords：Neutron-rich nuclei;neutron halo;Skyrme Hartree–Fock–Bogoliubov theory;Green's function method- 34
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Published：2023-08-16
NUCLEAR PHYSICS AND INTERDISCIPLINARY RESEARCH
- Abstract：A diffraction-limited storage ring with a multi-bend achromat lattice suffers from a small dynamic aperture for conventional off-axis injection. Thus, a longitudinal on-axis injection scheme based on a new type of crab cavity is proposed in this paper. Particle tracking simulations were performed to study the disturbance of the stored beam and the motion of the injected beam during the injection process. The possibility of multi-bunch injections was discussed. In addition, the effect of the long-range wake field induced by the stored beam was analyzed. A C-band standing-wave crab cavity was designed and produced as requested, and its field distribution was measured. The corresponding results are consistent with the simulation results.Keywords：On-axis injection;Crab cavity;Bump orbit;Wakefield
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Published：2023-08-16 - Abstract：The Hefei Advanced Light Facility (HALF) proposed by the National Synchrotron Radiation Laboratory is a green-field vacuum ultraviolet and soft X-ray diffraction-limited storage ring light source with a beam energy of 2.2 GeV and emittance goal of less than 100 pm⋅rad. Inspired by the ESRF-EBS hybrid multi-bend achromat (HMBA), SLS-2, and Diamond-II lattices, we propose and design a modified H6BA lattice as the baseline lattice of the HALF storage ring with 20 identical cells and a natural emittance of approximately 86 pm⋅rad. In this study, three other types of HMBA lattices comprising two H7BA lattices and a H6BA lattice are designed for HALF with the same number of cells. The main storage ring properties of these four HMBA lattices are compared. Because the intra-beam scattering (IBS) effect is significant in the HALF storage ring, we calculate and compare the equilibrium emittances of the four lattices with IBS included. These comparisons show that the present modified H6BA lattice, which has a relatively low equilibrium emittance and more straight sections, is preferred for the HALF storage ring after a comprehensive consideration.Keywords：Hefei Advanced Light Facility;Lattice design;Hybrid MBA lattice;Intra-beam scattering
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Published：2023-08-16
SYNCHROTRON RADIATION TECHNOLOGY AND APPLICATIONS
- Abstract：Main quadrupole magnets are critical for the Circular Electron and Positron Collider (CEPC), and are specifically designed as dual aperture quadrupole (DAQ) magnets. However, the field crosstalk between the two apertures presents challenges. As the CEPC will work at four beam energies of Z, W, Higgs and ttbar mode, the DAQ magnets will operate at four field gradients spanning from 3.18 to 12.63 T/m. The first short quadrupole magnet prototype with the bore diameter of 76 mm and magnetic length of 1.0 m revealed the problems of large magnetic field harmonics and a magnetic center shift within the beam energy range. Accordingly, a compensation method was proposed in this work to solve the field crosstalk effect. By adjusting the gap height at the middle of the two apertures, the field harmonics and magnetic center shift are significantly reduced. After optimization, the short prototype was modified using a new scheme. The field simulations are validated from the magnetic measurement results. Further, the multipole field meets the requirements at the four beam energies. The detailed magnetic field optimization, field harmonics adjustment, and measurement results are presented herein.Keywords：Dual aperture magnets;Field measurements;Crosstalk effect;Quadrupole magnet;Field harmonics;CEPC
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Published：2023-08-16 - Abstract：In certain exceptional cases, capillary samples must be used to measure X-ray absorption spectra (XAS). However, the inhomogeneous thickness of capillary samples causes XAS distortion. This study discusses the distortion and correction of the XAS curve caused by the inhomogeneous thickness of capillary samples. The relationship between the distorted XAS curve μ’deq (measured values) and the real absorption coefficient μsdeq (true values) of the sample was established. The distortion was slight and negligible when the vertical size (2h) of the X-ray beam spot was smaller than 60% of the capillary tube's inner diameter (2Rin). When h/Rin >1, X-ray leakage is inevitable and should be avoided during measurement. Partial X-ray leakage caused by an X-ray beam spot size larger than the inner diameter of the capillary tube leads to serious compressed distortion of the XAS curve. When h/Rin <1, the distorted XAS data were well corrected. Possible errors and their influence on the corrected XAS are also discussed. Simulations and corrections for distortions verify the feasibility and effectiveness of the corrected method.Keywords：XAS;Capillary;Compression distortion;Correction;Python
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Published：2023-08-16 - Abstract：In this study, an X-band standing-wave biperiodic linear accelerator was developed for medical radiotherapy that can accelerate electrons to 9 MeV using a 2.4 MW klystron. The structure works at π/2 mode and adopts magnetic coupling between cavities, generating the appropriate adjacent mode separation of 10 MHz. The accelerator is less than 600 mm long and constitutes 4 bunching cells and 29 normal cells. Geometry optimizations, full-scale radiofrequency (RF) simulations, and beam dynamics calculations were performed. The accelerator was fabricated and examined using a low-power RF test. The cold test results showed a good agreement with the simulation and actual measurement results. In the high-power RF test, the output beam current, energy spectrum, capture ratio, and spot size at the accelerator exit were measured. With the input power of 2.4 MW, the pulse current was 100 mA and the output spot root-mean-square radius was approximately 0.5 mm. The output kinetic energy was 9.04 MeV with the spectral FWHM of 3.5%, demonstrating the good performance of this accelerator.Keywords：Standing-wave accelerating structure;RF analysis;Thermal DC gun;Low-power RF test;High-power experiment
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Published：2023-08-16 - Abstract：Carbon ions, commonly referred to as particle therapy, have become increasingly popular in the last decade. Accurately predicting the range of ions in tissues is important for the precise delivery of doses in heavy-ion radiotherapy. Range uncertainty is currently the largest contributor to dose uncertainty in normal tissues, leading to the use of safety margins in treatment planning. One potential method is the direct relative stopping measurement (RSP) with ions. Hi’CT, a compact segmented full digital tomography detector using monolithic active pixel sensors (MAPS), was designed and evaluated using a 430-MeV/u high-energy carbon ion pencil beam in Geant4. The precise position of the individual carbon ion track can be recorded and reconstructed using a 30 × 30 μM small pixel pitch size. Two types of customized image reconstruction algorithms were developed, and their performances were evaluated using three different modules of CATPHAN 600-series phantoms. The RSP measurement accuracy of the tracking algorithm for different types of materials in the CTP404 module was less than 1%. In terms of spatial resolution, the tracking algorithm could achieve a 20% modulation transfer function (MTF) normalization value of CTP528 imaging results at 5 lp/cm, which is significantly better than that of the fast imaging algorithm (3 lp/cm). The density resolution obtained using the tracking algorithm of the customized CTP515 was approximately 10.5%. In conclusion, a compact digital heavy-ion CT (Hi’CT) system was designed, and its nominal performance was evaluated in a simulation. The RSP resolution and image quality provide potential feasibility for scanning most parts of an adult body or pediatric patient, particularly for head and neck tumor treatment.Keywords：Heavy-Ion Imaging;Computed tomography;Silicon Pixel Detectors;Monte Carlo;Phantoms;Radiotherapy;Image-guided;Tracking
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Published：2023-08-16
ACCELERATOR, RAY TECHNOLOGY AND APPLICATIONS
VIEWPOINT AND HIGHLIGHT
- Abstract：Bimetallic catalysts typically exploit unique synergetic effects between two metal species to achieve their catalytic effect. Understanding the mechanism of CO oxidation using hybrid heterogeneous catalysts is important for effective catalyst design and environmental protection. Herein, we report a Bi-Au/SiO2 tandem bimetallic catalyst for the oxidation of CO over the Au/SiO2 surface, which was monitored using near-ambient-pressure X-ray photoelectron spectroscopy. The Au-decorated SiO2 catalyst exhibited scarce activity in the CO oxidation reaction; however, the introduction of Bi to the Au/SiO2 system promoted the catalytic activity. The mechanism is thought to involve the dissociation O2 molecules in the presence of Bi, which results in spillover of the O species to adjacent Au atoms, thereby forming Auδ+. Further CO adsorption, followed by thermal treatment, facilitated the oxidation of CO at the Au-Bi interface, resulting in a reversible reversion to the neutral Au valence state. Our work provides insight into the mechanism of CO oxidation on tandem surfaces and will facilitate the rational design of other Au-based catalysts.Keywords：APXPS;CO oxidation;Au-Bi interface;Tandem catalysis;In-situ
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Published：2023-08-16 - Abstract：A ZrV2 alloy is typically susceptible to poisoning by impurity gases, which causes a considerable reduction in the hydrogen-storage properties of the alloy. In this study, the adsorption characteristics of oxygen on ZrV2 surfaces doped with Hf, Ti, and Pd are investigated, and the effect of oxygen on the hydrogen storage performance of the alloy was discussed. Subsequently, the adsorption energy, bond-length change, density of states, and differential charge density of the alloy before and after doping are analyzed using the first-principles method. The theoretical results show that Ti doping has a limited effect on the adsorption of oxygen atoms on the ZrV2 surface, whereas Hf doping decreases the adsorption energy of oxygen on the ZrV2 surface. Oxygen atoms are more difficult to adsorb at most adsorption sites on Pd-substituting surfaces, which indicates that Pd has the best anti-poisoning properties, followed by Hf. The analysis of the differential charge density and partial density of states show that the electron interaction between the oxygen atom and surface atom of the alloys is weakened, and the total energy is reduced after Hf and Pd doping. Based on theoretical calculations, the hydrogen-absorption kinetics of ZrV2, Zr0.9Hf0.1V2, and Zr(V0.9Pd0.1)2 alloys are studied in a hydrogen–oxygen mixture of 0.5 vol% O2 at 25℃. The experimental results show that the hydrogen-storage capacities of ZrV2, Zr0.9Hf0.1V2, and Zr(V0.9Pd0.1)2 decrease to 19%, 69%, and 80% of their original values, respectively. The order of alloy resistance to 0.5 vol% O2 poisoning is Zr(V0.9Pd0.1)2>Zr0.9Hf0.1V2>ZrV2. Pd retains its original hydrogen absorption performance to a greater extent than undoped surfaces, and it has the strongest resistance to poisoning, which is consistent with previous theoretical calculations.Keywords：Hydrogen storage;ZrV2;First-principles;Poisoning effect
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Published：2023-08-16
NUCLEAR CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR MEDICINE
- Abstract：China Fusion Engineering Test Reactor (CFETR) is China's self-designed and ongoing next-generation fusion reactor project. Tritium confinement systems in CFETR guarantee that the radiation level remains below the safety limit during tritium handling and operation in the fuel cycle system. Our tritium technology team is responsible for studying tritium transport behavior in the CFETR tritium safety confinement system of the National Key R&D Program of China launched in 2017, and we are conducting CFETR tritium plant safety analysis by using CFD software. In this paper, the tritium migration and removal behavior were studied under a postulated accident condition for the Tokamak Exhaust Processing (TEP) system of CFETR. The quantitative results of the transport behavior of tritium in the process room and glove box during the whole accident sequence (e.g., tritium release, alarm, isolation, and tritium removal) have been presented. The results support the detailed design and engineering demonstration-related research of CFETR tritium plant.Keywords：China Fusion Engineering Test Reactor (CFETR);Tokamak Exhaust Processing (TEP) system;Numerical simulation;Tritium transport behavior;Tritium confinement system;Accident condition
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Published：2023-08-16
NUCLEAR ENERGY SCIENCE AND ENGINEERING
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