Vol.36,

The particle identification (PID) of hadrons plays a crucial role in particle physics experiments, especially in flavor physics and jet tagging. The cluster-counting method, which measures the number of primary ionizations in gaseous detectors, is a promising breakthrough in PID. However, developing an effective reconstruction algorithm for cluster counting remains challenging. To address this challenge, we propose a cluster-counting algorithm based on long short-term memory and dynamic graph convolutional neural networks for the CEPC drift chamber. Experiments on Monte Carlo simulated samples demonstrate that our machine-learning-based algorithm surpasses traditional methods. It improves the K/π separation of PID by 10%, meeting the PID requirements of CEPC.

771

Neutron capture event imaging is a novel technique that has the potential to substantially enhance the resolution of existing imaging systems. This study provides a measurement method for neutron capture event distribution along with multiple reconstruction methods for super-resolution imaging. The proposed technology reduces the point-spread function of an imaging system through single-neutron detection and event reconstruction, thereby significantly improving imaging resolution. A single-neutron detection experiment was conducted using a highly practical and efficient ⁶LiF^-ZnS scintillation screen of a cold neutron imaging device in the research reactor. In milliseconds of exposure time, a large number of weak light clusters and their distribution in the scintillation screen were recorded frame by frame, to complete single-neutron detection. Several reconstruction algorithms were proposed for the calculations. The location of neutron capture was calculated using several processing methods such as noise removal, filtering, spot segmentation, contour analysis, and local positioning. The proposed algorithm achieved a higher imaging resolution and faster reconstruction speed, and single neutron super-resolution imaging was realized by combining single neutron detection experiments and reconstruction calculations. The results show that the resolution of the 100 μm thick ⁶LiF^-ZnS scintillation screen can be improved from 125 to 40 microns. This indicates that the proposed single-neutron detection and calculation method is effective and can significantly improve imaging resolution.

785

The purpose of this study was to evaluate the clinical application of a rotating pod and assess its dosimetric considerations, positional accuracy, and anatomical structure stability. A pre-dosimetric study conducted on 11 patients revealed the potential for lung dose reduction using the rotational pod. Subsequently, seven patients underwent treatment with the rotational pod, and the target coverage and organs at risk doses were compared with those of conventional methods. The positional accuracy of the rotational pod, in collaboration with the imaging guidance system, was analyzed. The Dice similarity coefficient (DSC) was used to assess the settlement of tumors, trachea, and thoracic vertebrae after rotation for 20 min. In the pre-dosimetric study, there was no statistically significant difference in the volume of the internal gross tumor volume receiving ≥99% of the prescription dose between the pod and conventional couch plans. However, compared to conventional couch plans, pod plans demonstrated a significant reduction in the average lung dose by 5 %-53 %(p<0.01). Patient accrual, comprising seven cases, revealed reduced lung doses (9 %-26 %) in four patients. For the other three patients, although there was no significant reduction in the lung dose, the use of the 90° beamline contributed to a decrease in the patient admission waiting time. The positional errors between the beams for lateral, longitudinal, vertical, ISO, pitch, and roll directions were 0.0 mm ± 5.3 mm,−1.2 mm ± 2.3 mm,−1.1 mm ± 2.7 mm, 0.0° ± 0.6°, −0.1° ± 0.5°, and 0.0° ± 0.8°, respectively. The DSC for the target region and thoracic vertebrae between CT images captured before and after a 20-min rotation was higher than 0.85, whereas the DSC for the trachea was approximately 0.8. The preliminary clinical application of the rotational pod for lung tumors in fixed ion beam lines shows promise for achieving target coverage, reducing lung dose, and maintaining position accuracy.

106

Neutron radiographic images (NRIs) typically suffer from multiple distortions, including various types of noise, geometric unsharpness, and white spots. Image quality assessment (IQA) can guide on-site image screening and even provide metrics for subsequent image processing. However, existing IQA methods for NRIs cannot effectively evaluate the quality of real NRIs with a specific distortion of white spots, limiting their practical application. In this paper, a novel no-reference IQA method is proposed to comprehensively evaluate the quality of real NRIs with multiple distortions. First, we construct large-scale NRI datasets with more than 20,000 images, including high-quality original NRIs and synthetic NRIs with various distortions. Next, an image quality calibration method based on visual salience and a local quality map is introduced to label the NRI dataset with quality scores. Finally, a lightweight convolutional neural network (CNN) model is designed to learn the abstract relationship between the NRIs and quality scores using the constructed NRI training dataset. Extensive experimental results demonstrate that the proposed method exhibits good consistency with human visual perception when evaluating both real NRIs and processed NRIs using enhancement and restoration algorithms, highlighting its application potential.

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The identification of ore grades is a critical step in mineral resource exploration and mining. Prompt gamma neutron activation analysis (PGNAA) technology employs gamma rays generated by the nuclear reactions between neutrons and samples to achieve the qualitative and quantitative detection of sample components. In this study, we present a novel method for identifying copper grade by combining the vision transformer (ViT) model with the PGNAA technique. First, a Monte Carlo simulation is employed to determine the optimal sizes of the neutron moderator, thermal neutron absorption material, and dimensions of the device. Subsequently, based on the parameters obtained through optimization, a PGNAA copper ore measurement model is established. The gamma spectrum of the copper ore is analyzed using the ViT model. The ViT model is optimized for hyperparameters using a grid search. To ensure the reliability of the identification results, the test results are obtained through five repeated ten-fold cross-validations. Long short-term memory (LSTM) and convolutional neural network (CNN) models are compared with the ViT method. These results indicate that the ViT method is efficient in identifying copper ore grades with average accuracy, precision, recall, F₁ score, and F₁(-) score values of 0.9795, 0.9637, 0.9614, 0.9625, and 0.9942, respectively. When identifying associated minerals, the ViT model can identify Pb, Zn, Fe, and Co minerals with identification accuracies of 0.9215, 0.9396, 0.9966, and 0.8311, respectively.

165

The multiple nuclides identification algorithm with low consumption and strong robustness is crucial for rapid radioactive source searching. This study investigates the design of a low-consumption multiple nuclides identification algorithm for portable gamma spectrometers. First, the gamma spectra of 12 target nuclides (including the background case) were measured to create training datasets. The characteristic energies, obtained through energy calibration and full-energy peak addresses, are utilized as input features for a neural network. A large number of single and multiple nuclide training datasets are generated using random combinations and small-range drifting. Subsequently, a multi-label classification neural network based on a binary cross-entropy loss function is applied to export the existence probability of certain nuclides. The designed algorithm effectively reduces the computation time and storage space required by the neural network and has been successfully implemented in a portable gamma spectrometer with a running time of t_r<2 s. Results show that, in both validation and actual tests, the identification accuracy of the designed algorithm reaches 94.8%, for gamma spectra with a dose rate of d≈0.5 μSv/h and a measurement time t_m=60 s. This improves the ability to perform rapid on-site nuclide identification at important sites.

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A thermionic gun is endowed with a long bunch tail, which presents challenges for the compact terahertz free electron laser (FEL) facility at the Huazhong University of Science and Technology. Owing to a large energy spread, the tail particles do not contribute to the radiation. In the original design, an x-direction slit is used in the dispersive section of the transport line to remove the tail particles. This paper presents an improved scheme to remove the tail by introducing an RF beam chopper system at the exit of the electron gun, to prevent a significant number of tail particles from entering the linac. The facility remains compact while effectively removing the tail of the bunch. The parameters of the beam chopper system are designed. Bunch parameters and radiation performance are analyzed via a start-to-end simulation. The findings indicate that 43% of the particles can pass through the beam chopper system for subsequent acceleration and transport, which saves the RF power, reduces beam loss in the linac, reduces background noise, and suppresses the sideband instability. Simultaneously, the beam chopper system causes an increase in beam emittance, energy spread, and an offset in the center of the bunch. These effects can be mitigated by a solenoid, linac, and steering coils. The simulation results for the FEL show that the micro-pulse energy is greater than 1.1 μJ in the frequency range of 2.8-9.7 THz, and the maximum micro-pulse energy is 1.28 μJ.

The main scientific payload of Macau Science Satellite-1B is a solar soft X-ray detection unit. To obtain an accurate solar X-ray spectrum, we have designed low-noise, high-throughput electronics. Solar radiation is detected using a low-leakage silicon drift detector (SDD), which is cooled to -30 ℃. The SDD output is processed using two parallel shaping amplifiers with peaking times of 315 ns and 65 ns. The amplifiers are designed using two-pole multiple-feedback active low-pass filters optimized to achieve a Bessel response. The differential output of the shaping amplifier generates a bipolar signal. The phase of the differential stage is tuned to ensure zero crossing corresponding to the peak of the shaping amplifier. A high-speed switch is inserted between the shaping amplifier and the peak-hold capacitor, and the peak value is maintained by turning off the switch. Fast and slow peak-hold circuits share a common ADC via time-division multiplexing. Both peak values are sampled for space-background rejection. Traditional pile-up detection methods cannot distinguish pulses that overlap in a fast channel. In this study, the differential of the “fast shaping” is selected, enabling the distinction of events separated by as little as 65 ns, which is crucial for solar flare detection. The energy resolution is measured to be 138 eV at 5.90 keV. The centroid drift is less than 3.6 eV between -5 ℃ and 20 ℃. Compared with other solar X-ray instruments, this study demonstrates improved energy resolution with a lower peaking time, indicating a higher solar flare detection capability.

Automatic phase setting is essential for modern linacs which have increasingly stringent time demands for beam tune-up and fault compensation. A key challenge in automatic phase setting is obtaining an accurate knowledge of the position and phase offsets of all cavities. This study proposes a beam-based method that employs time-of-flight (TOF) experiments to for simultaneous alignment and phase calibration of a superconducting hadron linac. The proposed method is verified using a CAFe II accelerator at the Institute of Modern Physics, where offset measurements enable rapid tune-up via automatic phase setting, and the output beam energies closely match the predicted values. The proposed method is able to address longitudinal position shifts within cryomodules due to cool-down, readily applicable to superconducting hadron linacs, and expected to be employed in the upcoming commissioning of CiADS and HIAF.

105

A super-radiant terahertz free-electron laser (THz-FEL) light source was developed for the first time in Thailand and Southeast Asia at the PBP-CMU Electron Linac Laboratory (PCELL) of Chiang Mai University. This radiation source requires relatively ultrashort electron bunches to produce intense coherent THz pulses. Three electron bunch compression processes are utilized in the PCELL accelerator system comprising pre-bunch compression in an alpha magnet, velocity bunching in a radio-frequency (RF) linear accelerator (linac), and magnetic bunch compression in a 180° acromat system. Electron bunch compression in the magnetic compressor system poses considerable challenges, which are addressed through the use of three quadrupole doublets. The strengths of the quadrupole fields significantly influence the rotation of the beam line longitudinal phase space distribution along the bunch compressor. Start-to-end beam dynamics simulations using the ASTRA code were performed to optimize the electron beam properties for generating super-radiant THz-FEL radiation. The operational parameters considered in the simulations comprise the alpha magnet gradient, linac RF phase, and quadrupole field strengths. The optimization results show that 10 - 16 MeV femtosecond electron bunches with a low energy spread (~0.2%), small normalized emittance (~ 15 πmm), and high peak current (165 - 247 A) can be produced by the PCELL accelerator system at the optimal parameters. A THz-FEL with sub-microjoule pulse energies can thus be obtained at the optimized electron beam parameters. The physical and conceptual design of the THz-FEL beamline were completed based on the beam dynamics simulation results. The construction and installation of this beamline are currently underway and expected to be completed by mid-2024. The commissioning of the beamline will then commence.

This article introduces a novel 20 V radiation-hardened high-voltage metal-oxide-semiconductor field-effect transistor (MOSFET) driver with an optimized input circuit and a drain-surrounding-source (DSS) structure. The input circuit of a conventional inverter consists of a thick-gate-oxide n-type MOSFET (NMOS). These conventional drivers can tolerate a total ionizing dose (TID) of up to 100 krad(Si). In contrast, the proposed comparator input circuit uses both a thick-gate- oxide p-type MOSFET (PMOS) and thin-gate-oxide NMOS to offer a high input voltage and higher TID tolerance. Because the thick-gate-oxide PMOS and thin-gate-oxide NMOS collectively provide better TID tolerance than the thick-gate-oxide NMOS, the circuit exhibits enhanced TID tolerance of >300 krad(Si). Simulations and experimental date indicate that the DSS structure reduces the probability of unwanted parasitic bipolar junction transistor activation, yielding a better single-event effect tolerance of over 81.8 MeV cm² mg^-1. The innovative strategy proposed in this study involves circuit and layout design optimization, and does not require any specialized process flow. Hence, the proposed circuit can be manufactured using common commercial 0.35 μm BCD processes.

740

Compared to other energy sources, nuclear reactors offer several advantages as a spacecraft power source, including compact size, high power density, and long operating life. These qualities make nuclear power an ideal energy source for future deep space exploration. A whole system model of the space nuclear reactor consisting of the reactor neutron kinetics, reactivity control, reactor heat transfer, heat exchanger, and thermoelectric converter, was developed. In addition, an electrical power control system was designed based on the developed dynamic model. The GRS method was used to quantitatively calculate the uncertainty of coupling parameters of the neutronics, thermal-hydraulics, and control system for the space reactor. The Spearman correlation coefficient was applied in the sensitivity analysis of system input parameters to output parameters. The calculation results showed that the uncertainty of the output parameters caused by coupling parameters had the most considerable variation, with a relative standard deviation < 2.01%. Effective delayed neutron fraction was most sensitive to electrical power. To obtain optimal control performance, the Non-dominated Sorting Genetic Algorithm method was employed to optimize the controller parameters based on the uncertainty quantification calculation. Two typical transient simulations were conducted to test the adaptive ability of the optimized controller in the uncertainty dynamic system, including 100% Full Power (FP) to 90% FP step load reduction transient and 5% FP/min linear variable load transient. The results showed that, considering the influence of system uncertainty, the optimized controller could improve the response speed and load following accuracy of electrical power control, in which the effectiveness and superiority have been verified.

109

Liquid hydrogen, known for its high energy density and eco-friendly properties, has garnered significant attention in the context of sustainable development and clean energy. A comprehensive understanding of its nucleation mechanisms and boiling heat transfer characteristics is crucial. However, current experimental and macroscopic simulation methods offer limited insights. This study employs molecular dynamics simulations to investigate the vaporization nucleation and boiling heat transfer properties of liquid hydrogen at the microscopic scale, with a focus on the effects of hydrogen film thickness, surface temperature, and wettability. The results indicate that hydrogen film thickness plays a critical role in nucleation. Thinner layers disrupt the shape of liquid films, leading to increased errors, whereas a thickness of 7 nm ensures film stability. Different heating methods and temperatures influence nucleation in various ways. Rapid heating results in a higher heat flux, while an increase in temperature under the same heating method accelerates nucleation, resulting in earlier nucleation and enhanced surface heat flow. Surfaces with varying wettability levels exhibit distinct nucleation behaviors. Specifically, an increase in α delays nucleation, causing a shift from the surface to within the liquid film due to stronger solid-liquid interaction forces. This study offers a microscale perspective on the nucleation and boiling processes of liquid hydrogen and provides valuable insights for phase transition studies.

113

The High-Energy Cosmic-Radiation Detector (HERD) is a planned experimental instrument at the Chinese Space Station. The silicon charge detector (SCD), a sub-detector in HERD, is used to detect cosmic-ray nuclei with a high charge resolution. In this study, we present a compact readout electronic system for the SCD that is designed for the HERD heavy-ion beam test. It comprises front-end readout electronics with 200 input channels as well as data-acquisition and data-management electronics. The test results showed that the SCD readout system had low noise with a silicon-strip detector connected. The dynamic range could be extended from 200 fC to 1200 fC and the cosmic-ray test was performed as expected.

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Cadmium telluride (CdTe), which has a high average atomic number and a unique band structure, is a leading material for room-temperature X/γ-ray detectors. Resistivity and mobility are the two most important properties of detector-grade CdTe single crystals. However, despite decades of research, the fabrication of high-resistivity and high-mobility CdTe single crystals faces persistent challenges, primarily because the stoichiometric composition cannot be well controlled owing to the high volatility of Cd under high-temperature conditions. This volatility introduces Te inclusions and cadmium vacancies (V_Cd) into the as-grown CdTe ingot, which significantly degrades the device performance. In this study, we successfully obtained detector-grade CdTe single crystals by simultaneously employing a Cd reservoir and chlorine (Cl) dopants via a vertical gradient freeze (VGF) method. By installing a Cd reservoir, we can maintain the Cd pressure under the crystal growth conditions, thereby preventing the accumulation of Te in the CdTe ingot. Additionally, the existence of the Cl dopant helps improve the CdTe resistivity by minimizing V_Cd density through the formation of an acceptor complex (Cl_Te-V_Cd)^-1. The crystalline quality of the obtained CdTe(Cl) was evidenced by a reduction in large Te inclusions, high optical transmission (60%), and a sharp absorption edge (1.456 eV). The presence of substitutional Cl dopants, known as ClTe+, simultaneously supports the record high resistivity of 1.5×10¹⁰ Ω and remarkable electron mobility of 1075±88 cm² V^-1 s^-1 simultaneously, has been confirmed by photoluminescence spectroscopy. Moreover, using our crystals, we fabricated a planar detector with μτ_e of (1.11 ± 0.04) × 10^-4 cm²/V, which performed with a decent radiation-detection feature. This study demonstrates that the vapor-pressure-controlled VGF method is a viable technical route for fabricating detector-grade CdTe crystals.

111

Metals in advanced nuclear reactors, such as W, often experience microcracks. However, the synergistic effects of high temperature, stress, and specialized structures can improve the self-healing ability of these metals. Microcrack healing is closely related to crack surface conditions. The order and disorder degree of crack surface atoms may affect crack stability. In this study, first-principles calculations, ab initio molecular dynamics, and surface thermodynamic theory were used to investigate the stability of grain boundary (GB) cracks at 0, 293, and 373 K. We compared the energy densities, crack attraction energies, and atomic diffusion behaviors of crack surfaces at ∑3 GBs with those at ∑5 GBs. Adsorption on the nanocrack surface determines the critical nanocrack width. It was found that Al ∑3(111) nanocracks heal at high temperatures, and this healing behavior is closely related to the crack surface energy. Meanwhile, the GB cracks of W heal in an orderly manner at 573 and 1203 K. BY contrast, the GB cracks of Ti remain unhealed. Finally, a high-temperature nanocrack expansion model was developed and used to predict crack behavior under applied stress at different temperatures.

105

Double perovskite matrix materials have recently attracted considerable interest due to their structural flexibility, ease of doping, and excellent thermal stability. While photoluminescence (PL) studies of rare-earth-doped double perovskites are common, research on their thermoluminescence (TL) properties is less extensive. This study synthesized a series of Y_2-xSm_xMgTiO₆ (0≤x≤0.1) samples using a high-temperature solid-state method. X-ray diffraction (XRD) analysis confirmed a monoclinic crystal structure (space group P2₁/n), with Sm³⁺ ions substituting for Y³⁺ ions in Y₂MgTiO₆. The PL results indicated that the optimal doping concentration was Y_1.95Sm_0.05MgTiO₆, exhibiting emission peaks at 568, 605, 652, and 715 nm under 409 nm blue light excitation. The TL measurements for different doping concentrations showed that the Y_1.98Sm_0.02MgTiO₆ phosphors exhibited the strongest TL signals. The TL peaks observed at 530 and 610 K correspond to defects in the matrix and Sm³⁺ dopants, respectively. The T_m-T_stop analysis revealed that the TL curve of Y_1.98Sm_0.02MgTiO₆ phosphors was a superposition of seven peaks. Computerized glow curve deconvolution (CGCD) was performed on the TL of the sample according to the results of three-dimensional thermoluminescence spectra (3D-TL) and T_m-T_stop, the trap depths in the sample were estimated to range from 0.69 eV to 1.49 eV. Additionally, the lifetimes of each overlapping peak were calculated using the fitting parameters. Furthermore, the dose-response test showed that the saturation dose of the sample was high (9956 Gy). Therefore, this material can serve as a thermoluminescent dosimeter for high-dose measurements. The saturation dose for the lowest-temperature overlapping peak was 102 Gy, which correlated with its specific energy level lifetime, whereas the other overlapping peaks also exhibited favorable linear relationships.

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This study explores the phenomenon of shape coexistence in nuclei around ¹⁷²Hg, with a focus on the isotopes ¹⁷⁰Pt, ¹⁷²Hg, and ¹⁷⁴Pb, as well as the ¹⁷⁰Pt to ¹⁸⁰Pt isotopic chain. Utilizing a macro-microscopic approach that incorporates the Lublin-Strasbourg Drop model combined with a Yukawa-Folded potential and pairing corrections, we analyze the potential energy surfaces (PESs) to understand the impact of pairing interaction. For¹⁷⁰Pt, the PES exhibited a prolate ground-state, with additional triaxial and oblate-shaped isomers. In ¹⁷²Hg, the ground-state deformation transitions from triaxial to oblate with increasing pairing interaction, demonstrating its nearly γ-unstable nature. Three shape isomers (prolate, triaxial, and oblate) were observed, with increased pairing strength leading to the disappearance of the triaxial isomer. ¹⁷⁴Pb exhibited a prolate ground-state that became increasingly spherical with stronger pairing. While shape isomers were present at lower pairing strengths, robust shape coexistence was not observed. For realistic pairing interaction, the ground-state shapes transitioned from prolate in ¹⁷⁰Pt to a coexistence of γ-unstable and oblate shapes in ¹⁷²Hg, ultimately approaching spherical symmetry in ¹⁷⁴Pb. A comparison between Exact and Bardeen-Cooper-Schrieffer (BCS) pairing demonstrated that BCS pairing tends to smooth out shape coexistence and reduce the depth of the shape isomer, leading to less pronounced deformation features. The PESs for even-even ^170-180Pt isotopes revealed significant shape evolution. ¹⁷⁰Pt showed a prolate ground-state, whereas ¹⁷²Pt exhibited both triaxial and prolate shape coexistence. In ¹⁷⁴Pt, the ground-state was triaxial, coexisted with a prolate minimum. For ¹⁷⁶Pt, a γ-unstable ground-state coexists with a prolate minimum. By ¹⁷⁸Pt and ¹⁸⁰Pt, a dominant prolate minimum emerged. These results highlight the role of shape coexistence and γ-instability in the evolution of nuclear structure, especially in the mid-shell region. These findings highlight the importance of pairing interactions in nuclear deformation and shape coexistence, providing insights into the structural evolution of mid-shell nuclei.

114

Nuclear mass is an important property in both nuclear and astrophysics. In this study, we explore an improved mass model that incorporates a higher-order term of symmetry energy using algorithms. The sequential least squares programming (SLSQP) algorithm augments the precision of this multinomial mass model by reducing the error from 1.863 MeV to 1.631 MeV. These algorithms were further examined using 200 sample mass formulae derived from the δE term of the E_isospin mass model. The SLSQP method exhibited superior performance compared to the other algorithms in terms of errors and convergence speed. This algorithm is advantageous for handling large-scale multiparameter optimization tasks in nuclear physics.

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We developed a dedicated data analysis framework for silicon strip detector telescopes (SSDTs) of the Compact Spectrometer for Heavy-IoN Experiments (CSHINE) that addresses the challenges of processing complex signals. The framework integrates advanced algorithms for precise calibration, accurate particle identification, and efficient event reconstruction, aiming to account for critical experimental factors such as charge-sharing effects, multi-hit event resolution, and detector response nonuniformity. Its robust performance was demonstrated through the successful analysis of light-charged particles in the 25 MeV/u ⁸⁶Kr + ¹²⁴Sn experiment conducted at the first Radioactive Ion Beam Line in Lanzhou, allowing for precise extraction of physical observables, including energy, momentum, and particle type. Furthermore, utilizing the reconstructed physical information, such as the number of effective physical events and energy spectra to optimize the track recognition algorithm, the final track recognition efficiencies of approximately 90% were achieved. This framework establishes a valuable reference methodology for SSDT-based detector systems in heavy-ion reaction experiments, thereby significantly enhancing the accuracy and efficiency of data analysis in nuclear physics research.

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