Vol.34,

The purpose of this study was to design a rapid cycling synchrotron, making it capable of proton beam ultra-high dose rate irradiation, inspired by laser accelerators. The design had to be cheap and simple. We consider our design from six aspects: the lattice, injection, extraction, space charge effects, eddy current effects and energy switching. Efficiency and particle quantity must be addressed when injected. The space charge effects at the injection could affect particles’ number. The eddy current effects in the vacuum chambers would affect the magnetic field itself and generate heat, all of which need to be taken into account. Fast extraction can obtain 10¹⁰ protons/pulse, equal to instantaneous dose rate up to 10⁷ Gy/s in a very short time, while changing various extraction energies rapidly and easily to various deposition depths. In the further research we expect to combine a delivery system with this accelerator to realize the FLASH irradiation.

453

Man-Zhou Zhang，De-Ming Li，Li-Ren Shen，Hai-Rong Zhang，Zhi-Ling Chen，Han-Wen Du，Ming Gu，Rui Li，De-Kang Liu，Yue-Hu Pu，Jun-Feng Yu，Jian-Feng Chen，Chu Chen，Chun-Long Guo，Hao Guo，Ge-Yang Jiang，Zhi-Qiang Jiang，Lin Jin，Wen-Jing Li，Xiu-Fang Li，Ye Lin，Ming Liu，Yong-Hao Liu，Ya-Juan Liu，Ming Lv，Qing-Ru Mi，Lian-Hua Ouyang，Wei-Guo Shi，Hang Shu，Qi-Sheng Tang，Kun Wang，Zhi-Shan Wang，Jun Wu，Xiao-Bing Wu，Jia-Qiang Xu，Wen-Zhen Xu，Chong-Xian Yin，Cheng Yu，Ren-Xian Yuan，Qi-Bing Yuan，Hai-Qun Zhang，Miao Zhang，Wen-Zhi Zhang，Li-Ying Zhao，Wei-Min Zhou，Shou-Xian Fang，Xi-Dong Sun，Zhen-Tang Zhao

Because of its excellent dose distribution, proton therapy is becoming increasingly popular in the medical application of cancer treatment. A synchrotron-based proton therapy facility was designed and constructed in Shanghai. The synchrotron, gantry beam delivery system, and other technical systems were commissioned and reached their expected performances. After a clinical trial of 47 patients was finished, the proton therapy facility obtained a registration certificate from the National Medical Products Administration. The characteristics of the accelerator and treatment systems are described in this article.

542

Polarized neutrons play an indispensable role in neutron scattering research, and have been incorporated into various neutron diffractometers and spectrometers. Recognizing the importance of polarized neutrons, the China Spallation Neutron Source (CSNS) has dedicated resources for developing its own capabilities for polarized neutron techniques. Hence, a polarized neutron development platform was allocated to the BL-20 beam port at CSNS for the purpose of facilitating new technological developments and calibration of instruments. Here, we report the progress we have made in terms of using the established development platform at BL-20, including the characterization of neutron spin filter cells manufactured at CSNS, the calibration of self-developed polarized neutron instruments, performance of the polarized neutron technique applied to beamlines, and associated simulation work for beamline magnetic field environments. These results demonstrate the capability of the CSNS to develop time-of-flight polarized neutron instruments and techniques in-house, which will be incorporated into the construction of CSNS neutron beamlines.

424

In the future, the Very Large Area gamma-ray Space Telescope (VLAST) is expected to observe high-energy electrons and gamma rays in the MeV to TeV range with unprecedented acceptance. As part of the detector suite, a high-energy imaging calorimeter (HEIC) is currently being developed as a homogeneous calorimeter that utilizes long bismuth germanate (BGO) scintillation crystals as both absorbers and detectors. To accurately measure the energy deposition in the BGO bar of HEIC, a high-dynamic-range readout method using a silicon photoMultiplier (SiPM) and multiphotodiode (PD) with different active areas has been proposed. A prototype readout system that adopts multichannel charge measurement ASICs was also developed to read out the combined system of SiPMs and PDs. Preliminary tests confirmed the feasibility of the readout scheme, which is expected to have a dynamic range close to 10⁶.

380

In this experimental study, involving deuterium–deuterium fusion neutron emission spectroscopy (NES) measurement on the experimental advanced superconducting tokamak (EAST), a liquid scintillator detector (BC501A) was employed. This decision was based on the detector's superior sensitivity, optimal time-response, and its exceptional n-γ discrimination capability. This detector emits fast pulse signals that are as narrow as 100 ns, with high count rates that can peak at several Mcps. However, conventional nuclear circuits faced challenges in performing pulse height analysis, n–γ pulse shape discrimination (PSD), and in recording the entire pulse waveform under such high-count-rate conditions. To address these challenges, a high-speed digital pulse signal acquisition and processing system was designed. The system was developed around a micro-telecommunications computing architecture (MTCA). Within this structure, a signal acquisition and processing (SAQP) module communicated through PCI Express (PCIe) links, achieving a bandwidth of up to 1.6 GB/s. To accurately capture the detailed shape of the pulses, four channels of analog-to-digital converters (ADCs) were used, each with a 500-MSPS sampling rate and a 14-bit resolution, ensuring an accuracy that surpassed 11 bits. An n-γ discrimination algorithm, based on the two-gate integral method, was also developed. Implemented within field programmable gate arrays (FPGA), this algorithm provided a real-time n-γ discrimination spectrum for pulse height analysis. The system underwent rigorous testing in a laboratory setting and during an EAST experiment. The results confirmed that the innovative SAQP system can satisfy the demanding requirements of high-parameter experiments, manage count rates of up to 2 Mcps, execute real-time n-γ discrimination algorithms, and record entire pulse waveforms without any data loss.

575

To enhance the accuracy of 2πα and 2πβ particle surface emission rate measurements and address the identification issues of nuclides in conventional methods, this study introduces two artificial neural network (ANN) algorithms: back propagation (BP) and genetic algorithm-based back propagation (GA-BP). These algorithms classify pulse signals from distinct α and β particles. Their discrimination efficacy is assessed by simulating standard pulse signals and those produced by contaminated sources, mixing α and β particles within the detector. This study initially showcases energy spectrum measurement outcomes, subsequently tests the ANNs on the measurement and validation datasets, and contrasts the pulse shape discrimination efficacy of both algorithms. Experimental findings reveal that the proportional counter's energy resolution is not ideal, thus rendering energy analysis insufficient for distinguishing between 2πα and 2πβ particles. The BP neural network realizes approximately 99% accuracy for 2πα particles and approximately 95% for 2πβ particles, thus surpassing the GA-BP's performance. Additionally, the results suggest enhancing β particle discrimination accuracy by increasing the digital acquisition card's threshold lower limit. This study offers an advanced solution for the 2πα and 2πβ surface emission rate measurement method, presenting superior adaptability and scalability over conventional techniques.

697

This study introduces a novel algorithm to detect and identify radioactive materials in urban settings using time-series detector response data. To address the challenges posed by varying backgrounds and to enhance the quality and reliability of the energy spectrum data, we devised a temporal energy window. This partitioned the time-series detector response data, resulting in energy spectra that emphasize the vital information pertaining to radioactive materials. We then extracted characteristic features of these energy spectra, relying on the formation mechanism and measurement principles of the gamma-ray instrument spectrum. These features encompassed aggregated counts, peak-to-flat ratios, and peak-to-peak ratios. This methodology not only simplified the interpretation of the energy spectra’s physical significance but also eliminated the necessity for peak searching and individual peak analyses. Given the requirements of imbalanced multi-classification, we created a detection and identification model using a weighted k-nearest neighbors (KNN) framework. This model recognized that energy spectra of identical radioactive materials exhibit minimal inter-class similarity. Consequently, it considerably boosted the classification accuracy of minority classes, enhancing the classifier’s overall efficacy. We also executed a series of comparative experiments. Established methods for radionuclide identification classification, such as standard k-nearest neighbors (KNN), support vector machine (SVM), Bayesian network, and random tree, were used for comparison purposes. Our proposed algorithm realized an F1 measure of 0.9868 on the time-series detector response data, reflecting a minimum enhancement of 0.3% in comparison to other techniques. The results conclusively show that our algorithm outperforms others when applied to time-series detector response data in urban contexts.

568

Multi-objective evolutionary algorithms (MOEAs) are typically used to optimize two or three objectives in the accelerator field and perform well. However, the performance of these algorithms may severely deteriorate when the optimization objectives for an accelerator are equal to or greater than four. Recently, many-objective evolutionary algorithms (MaOEAs) that can solve problems with four or more optimization objectives have received extensive attention. In this study, two diffraction-limited storage ring (DLSR) lattices of the Extremely Brilliant Source (ESRF-EBS) type with different energies were designed and optimized using three MaOEAs and a widely used MOEA. The initial population was found to have a significant impact on the performance of the algorithms and was carefully studied. The performances of the four algorithms were compared, and the results demonstrated that the grid-based evolutionary algorithm (GrEA) had the best performance. MaOEAs were applied in many-objective optimization of DLSR lattices for the first time, and lattices with natural emittances of 116 pm∙rad and 23 pm∙rad were obtained at energies of 2 GeV and 6 GeV, respectively, both with reasonable dynamic aperture and local momentum aperture (LMA). This work provides a valuable reference for future many-objective optimization of DLSRs.

495

The thermodynamic properties of charged particles, such as the energy density, pressure, entropy density, particle density, and squared speed of sound at the kinetic freeze-out in the Au + Au collisions from the relativistic heavy ion collider (RHIC) beam energy scan program (sNN=7.7–200 GeV) and in the Cu + Cu collisions at sNN=62.4, 200 GeV are studied using the thermodynamically consistent Tsallis distribution. The energy density, pressure, and particle density decrease monotonically with the collision energy for the same collision centrality; These properties also decrease monotonically from the central to peripheral collisions at the same collision energy. While the scaled energy density ε/T⁴ and scaled entropy density s/T³ demonstrate the opposite trend with the collision energy for the same collision centrality. There is a correlation between ε/T⁴ and s/T³ at the same centrality. In addition, the squared speed of sound was calculated to determine that all the collision energies share nearly the same value at different collision centralities.

560

In this study, we developed a neural network that incorporates a fully connected layer with a convolutional layer to predict the nuclear charge radii based on the relationships between four local nuclear charge radii. The convolutional neural network (CNN) combines the isospin and pairing effects to describe the charge radii of nuclei with A ≥ 39 and Z ≥ 20. The developed neural network achieved a root–mean–square (RMS) deviation of 0.0195 fm for a dataset with 928 nuclei. Specifically, the CNN reproduced the trend of the inverted parabolic behavior and odd–even staggering observed in the calcium isotopic chain, demonstrating reliable predictive capability.

737

Lambda polarization can be measured through its self-analyzing weak decay, making it an ideal candidate for studying spin effects in high-energy scattering. In lepton-nucleon deep inelastic scattering (DIS), Lambda polarization measurements can probe polarized parton distribution functions (PDFs) and polarized fragmentation functions (FFs). One of the most promising facilities for high-energy nuclear physics research is the proposed Electron-ion collider in China (EicC). As a next-generation facility, EicC is set to advance our understanding of nuclear physics to new heights. In this article, we study the Lambda production in electron-proton collisions at the EicC energy, in particular the reconstruction of Lambda based on the performance of the designed EicC detector. In addition, taking spontaneous transverse polarization as an example, we provide a theoretical prediction with a statistical projection based on one month of EicC data, offering valuable insights into future research prospects.

485

The total absolute cross sections of single- and double-electron capture (SEC and DEC) in the collisions of He²⁺ with He and Ne⁸⁺ with O₂, N₂, and CH₄ were studied in the energy ranges 3.5 to 50 keV/u and 2.8 to 40 keV/u, respectively. Through a deep analysis of the experimental systematic uncertainties in the measurement procedure and data evaluation, the error in the experimental results of the SEC cross sections is less than 9%. Within the uncertainties, the present results of the He²⁺ -He collision show good consistency with previous measurements, validating the experimental system and paving the way for precise measurements of EC cross sections for a variety of ions and neutral gases. The present measurements allow for a test of EC theory and provide crucial EC cross section data for the establishment of plasma models in fusion research and astrophysical X-ray studies.

364

We applied KF Particle, a Kalman Filter package for secondary vertex finding and fitting, to strange and open charm hadron reconstruction in heavy-ion collisions in the STAR experiment. Compared to the conventional helix swimming method used in STAR, the KF Particle method considerably improved the reconstructed Λ, Ω, and D⁰ significance. In addition, the Monte Carlo simulation with STAR detector responses could adequately reproduce the topological variable distributions reconstructed in real data using the KF Particle method, thereby retaining substantial control of the reconstruction efficiency uncertainties for strange and open charm hadron measurements in heavy-ion collisions.

568

In this study, we constructed two annular detector arrays comprising 24 wedge-shaped CsI(Tl) crystals, and tested them using an α source and radioactive beams of ^14-16C on a CD₂ target. We compared the properties of a CsI(Tl) crystal encapsulated with various reflectors, revealing that using the 80-μm-thick ESR film to pack the CsI(Tl) crystal yielded the largest light output with the smallest non-uniformity in light output (ΔLO). For the 24 CsI(Tl) detectors with the 80-μm-thick ESR films, the average energy resolution improved as the average light output increased; however, it deteriorated as the ΔLO value increased. To form two annular Si-CsI(Tl) telescopes for identifying the light-charged particles, the ΔLO value and energy resolution of each CsI(Tl) detector were maintained under 20% and 7.7%, respectively. These telescopes were tested for the first time in a direct nuclear reaction experiment using ^14-16C + d. The results demonstrated that the Z = 1 and Z = 2 charged particles were adequately discriminated by the telescopes using the standard Δ E-E method.

408

We systematically calculated the multinucleon transfer reactions of ²⁰⁸Os, ²⁰⁸Pt, ²⁰⁸Hg, ²⁰⁸Pb,²⁰⁸Po, ²⁰⁸Rn, ²⁰⁸Ra, and ^132,136Xe when bombarded on ²³²Th and ²⁴⁸Cm at Coulomb barrier energies within the dinuclear system model. These results are in good agreement with the available experimental data. The influence of Coulomb and shell effects on actinide production in these reactions has been rigorously studied. We calculated and analyzed the potential energy surface (PES) and total kinetic energy (TKE) mass distributions for the reactions involving ²⁰⁸Hg, ²⁰⁸Pb, and ²⁰⁸Po with ²⁴⁸Cm and ²³²Th. The PES and TKE spectra shed light on the fragment formation mechanisms in multinucleon transfer reactions, with clear indications of isospin and shell effects. The production cross-sections for multinucleon transfer products show a strong dependence on isobar projectiles with a mass number A=208. Isobar projectiles with high N/Z ratios are advantageous for generating neutron-rich target-like fragments. Conversely, products induced by isobar projectiles with larger charge numbers tend to shift toward proton-rich regions. The intertwining of the Coulomb potential and shell effect is evident in the production cross-sections of actinide isotopes. Drawing from reactions induced by radioactive projectiles, we anticipate the discovery of several new actinide isotopes near the nuclear drip lines, extending our reach into the superheavy nuclei domain.

437

Steam generator tube rupture (SGTR) accident is an important scenario needed to be considered in the safety analysis of lead-based fast reactors. When the steam generator tube breaks close to the main pump, water vapor will enter the reactor core, resulting in a two-phase flow of heavy liquid metal and water vapor in fuel assemblies. The thermal-hydraulic problems caused by the SGTR accident may seriously threaten reactor core’s safety performance. In this paper, the open source CFD calculation software OpenFOAM was used to encapsulate the improved Euler method into the self-developed solver LBEsteamEulerFoam. By changing different heating boundary conditions and inlet coolant types, the two-phase flow in the fuel assembly with different inlet gas content was simulated under various accident conditions. The calculation results show that the water vapor may accumulate in edge and corner channels. With the increase of inlet water vapor content, outlet coolant velocity increases gradually. When the inlet water vapor content is more than 15%, the outlet coolant temperature rises sharply with strong temperature fluctuation. When the inlet water vapor content is in the range of 5% to 20%, the upper part of the fuel assembly will gradually accumulate to form large bubbles. Compared with the VOF method, Euler method has higher computational efficiency. However, Euler method may cause an underestimation of the void fraction, so it still needs to be calibrated with future experimental data of the two phase flow in fuel assembly.

451

Machine learning-based modeling of reactor physics problems has attracted increasing interest in recent years. Despite some progress in one-dimensional problems, there is still a paucity of benchmark studies that are easy to solve using traditional numerical methods albeit still challenging using neural networks for a wide range of practical problems. We present two networks, namely the Generalized Inverse Power Method Neural Network (GIPMNN) and Physics-Constrained GIPMNN (PC-GIPIMNN) to solve K-eigenvalue problems in neutron diffusion theory. GIPMNN follows the main idea of the inverse power method and determines the lowest eigenvalue using an iterative method. The PC-GIPMNN additionally enforces conservative interface conditions for the neutron flux. Meanwhile, Deep Ritz Method (DRM) directly solves the smallest eigenvalue by minimizing the eigenvalue in Rayleigh quotient form. A comprehensive study was conducted using GIPMNN, PC-GIPMNN, and DRM to solve problems of complex spatial geometry with variant material domains from the field of nuclear reactor physics. The methods were compared with the standard finite element method. The applicability and accuracy of the methods are reported and indicate that PC-GIPMNN outperforms GIPMNN and DRM.

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