Nuclear Science and Techniques

As a cluster overlap amplitude, the reduced-width amplitude is an important physical quantity for analyzing clustering in the nucleus depending on specified channels and has been calculated and widely applied in nuclear cluster physics. In this review, we briefly revisit the theoretical framework for calculating the reduced-width amplitude, as well as the outlines of cluster models to obtain microscopic or semi-microscopic cluster wave functions. We also introduce the recent progress related to cluster overlap amplitudes, including the implementation of cross-section estimation and extension to three-body clustering analysis. Comprehensive examples are provided to demonstrate the application of the reduced-width amplitude in analyzing clustering structures.

In response to the demand for rapid geometric modeling in Monte Carlo radiation transportation calculations for large-scale and complex geometric scenes, functional improvements, and algorithm optimizations were performed using CAD-to-Monte Carlo geometry conversion (CMGC) code. Boundary representation (BRep) to constructive solid geometry (CSG) conversion and visual CSG modeling were combined to address the problem of non-convertible geometries such as spline surfaces. The splitting surface assessment method in BRep-to-CSG conversion was optimized to reduce the number of Boolean operations using an Open Cascade. This, in turn, reduced the probability of CMGC conversion failure. The auxiliary surface generation algorithm was optimized to prevent the generation of redundant auxiliary surfaces that cause an excessive decomposition of CAD geometry solids. These optimizations enhanced the usability and stability of the CMGC model conversion. CMGC was applied successfully to the JMCT transportation calculations for the conceptual designs of five China Fusion Engineering Test Reactor (CFETR) blankets. The rapid replacement of different blanket schemes was achieved based on the baseline CFETR model. The geometric solid number of blankets ranged from hundreds to tens of thousands. The correctness of the converted CFETR models using CMGC was verified through comparisons with the MCNP calculation results. The CMGC supported radiation field evaluations for a large urban scene and detailed ship scene. This enabled the rapid conversion of CAD models with thousands of geometric solids into Monte Carlo CSG models. An analysis of the JMCT transportation simulation results further demonstrated the accuracy and effectiveness of the CMGC.

A thermal–hydraulic model was developed to analyze the three-dimensional (3D) temperature field of a graphite-moderated channel-type molten salt reactor (GMC-MSR). This model solves the temperature distribution of both the graphite moderator and fuel salt using a single convection–diffusion equation. Heat transfer at the interface between the fuel salt and graphite was addressed by introducing an additional thermal resistance component at the interface and modifying the anisotropic thermal conductivity of the fuel salt. The mass flow distribution in different flow passages was determined by adjusting the mass flow rate until a uniform pressure drop was achieved across all fuel channels. This thermal–hydraulic model, constructed on COMSOL Multiphysics, was verified by comparing its temperature results with those from the RELAP5 code across two demonstration cases. A steady-state thermal–hydraulic simulation of this model was performed to evaluate the conceptual design of a 2-MW experimental molten salt reactor (2MW-MSR). In addition, detailed discussions of the 3D temperature field, heat flux, and mass flow distribution of the 2MW-MSR were presented. This model allows for a comprehensive 3D thermal–hydraulic analysis of the GMC-MSR. Moreover, it only requires the solution of a single convection–diffusion equation, which makes it invaluable for GMC-MSR design.

DNA double-strand breaks (DSBs) may result in cellular mutations, apoptosis, and cell death, making them critical determinants of cellular survival and functionality, as well as major mechanisms underlying cell death. The success of nanodosimetry lies in the reduction in the number of modeling parameters to be adjusted for the model to predict experimental data on radiation biology. Based on this background, this study modified and simplified the logistic nanodosimetry model (LNDM) based on radiation-induced DSB probability. The probability distribution of ionization cluster size P(ν|Q) under irradiation with carbon-ion beams was obtained through a track-structure Monte Carlo (MC) simulation, and then the nanodosimetric quantities and DSB probability were calculated. Combining the assumptions of the linear quadratic (LQ) model and LNDM, DSB probability-based modification and simplification of the LNDM were conducted. Additionally, based on the radiobiological experimental data of human salivary gland (HSG), Chinese hamster lung (V79), and Chinese hamster ovary (CHO-K1) cells, the least-squares method was used to optimize the parameters of the modified LNDM (mLNDM). The mLNDM accurately reproduced the experimental data of HSG, V79, and CHO-K1 cells, and the results showed that the model parameters r and m₀ were independent of the cell type, that is, the biological effects of cells with different radiosensitivities can be characterized by adjusting only the model parameters k and P_{s → l}. Compared with HSG and CHO-K1 cells, V79 cells had smaller k and P_{s → l} values, indicating that that DSBs have a lower probability of eventually causing lethal damage, and sub-lethal events are less likely to interact to form lethal events, thereby having radioresistant characteristics. Compared with the LNDM, the mLNDM eliminates the tedious derivation process and connects the quantities characterizing radiation quality at the nanoscale level using radiation biological effects in a more direct and easy-to-understand manner, thus providing a simpler and more accurate method for calculating relative biological effectiveness for ion-beam treatment planning.

A dual-harmonic acceleration system is utilized to mitigate the space-charge effect in the rapid-cycling synchrotron of the China Spallation Neutron Source upgrade project (CSNS-II). A magnetic alloy (MA)-loaded cavity with a high accelerating gradient is developed to satisfy the requirements of dual-harmonic acceleration and provide the necessary second-harmonic cavity voltage. However, the MA-loaded cavity exhibits a wideband frequency response, resulting in numerous higher harmonics in the radio-frequency (RF) voltage. These higher harmonics are caused by both the beam-loading effect and distorted amplifier current, which distort the RF bucket, increase the power dissipation in the cavity, and lower the gradient. To address these issues, a multiharmonic independent feedback-control approach is implemented to compensate for higher harmonics. The effectiveness of this control strategy is validated experimentally. This study provides details regarding the feedback-control design and presents the commissioning results.

Energy resolution calibration is crucial for gamma-ray spectral analysis, as measured using a scintillation detector. A locally constrained regularization method was proposed to determine the resolution calibration parameters. First, a Monte Carlo simulation model consistent with an actual measurement system was constructed to obtain the energy deposition distribution in the scintillation crystal. Subsequently, the regularization objective function is established based on weighted least squares and additional constraints. Additional constraints were designed using a special weighting scheme based on the incident gamma-ray energies. Subsequently, an intelligent algorithm was introduced to search for the optimal resolution calibration parameters by minimizing the objective function. The most appropriate regularization parameter was determined through mathematical experiments. When the regularization parameter was 30, the calibrated results exhibited the minimum RMSE. Simulations and test-pit experiments were conducted to verify the performance of the proposed method. The simulation results demonstrate that the proposed algorithm can determine resolution calibration parameters more accurately than the traditional weighted least squares, and the test pit experimental results show that the R-squares between the calibrated and measured spectra are larger than 0.99. The accurate resolution calibration parameters determined by the proposed method lay the foundation for gamma-ray spectral processing and simulation benchmarking.

The heavy-ion accelerator facility (HIAF) under construction in China will produce various stable and intense radioactive beams with energies ranging from MeV/u to GeV/u. The ion-linac (iLinac) accelerator, which will serve as the injector for the HIAF, is a superconducting heavy-ion accelerator containing 13 cryomodules. It will operate in either continuous wave mode or pulsed mode, with a beam current ranging from 0.01 emA to 1 emA. The beam position monitor (BPM) is crucial for this high-beam-power machine, which requires precise beam control and a very small beam loss of less than 1 W/m, especially inside the cryomodules of this unique beam instrument. Nearly 70 BPMs will be installed on the iLinac. New digital beam position and phase measurement (DBPPM) electronics based on a heterogeneous multiprocessing platform system-on-chip (MPSoC) has been developed to provide accurate beam trajectory and phase measurements as well as beam interlocking signals for a fast machine protection system (MPS). The DBPPM comprises an analog front-end (AFE) board in field programmable gate array (FPGA) mezzanine-connector (FMC) form factor, along with a digital signal processing board housed within a 2U 19" chassis. To mitigate radio frequency (RF) leakage effects from high-power RF systems in certain scenarios, beam signals undergo simultaneous processing at both fundamental and second-harmonic frequencies. A dynamic range from -65 dBm to 0 dBm was established to accommodate both weak beam commissioning and high-intensity operational demands. Laboratory tests demonstrated that at input power levels exceeding -45 dBm, the phase resolution surpasses 0.05, and the position resolution exceeds 5 μm. These results align well with the stipulated measurement requirements. Moreover, the newly developed DBPPM has self-testing and self-calibration functions that are highly helpful for the systematic evaluation of numerous electronic components and fault diagnosis equipment. In addition, the DBPPM electronics implements a 2D non-linear polynomial correction on the FPGA and can collect accurate real-time position measurements at large beam offsets. This newly developed DBPPM electronics has been applied to several Linac machines, and the results from beam measurements show high performance, good long-term stability, and high reliability. In this paper, a detailed overview of the architecture, performance, and proof-of-principle measurement of the beams is presented.

In the exploration of celestial bodies, such as Mars, the Moon, and asteroids, X-ray fluorescence analysis has emerged as a critical tool for elemental analysis. However, the varying selection rules and excitation sources introduce complexity. Specifically, these discrepancies can cause variations in the intensities of the characteristic spectral lines emitted by identical elements. These variations, compounded by the minimal energy spacing between these spectral lines, pose substantial challenges for conventional silicon drift detectors (SDD), hindering their ability to accurately differentiate these lines and provide detailed insights into the material structure. To overcome this challenge, a cryogenic X-ray spectrometer based on transition-edge sensor (TES) detector arrays is required to achieve precise measurements. This study measured and analyzed the K-edge characteristic lines of copper and the diverse L-edge characteristic lines of tungsten using a comparative analysis of the electron and X-ray excitation processes. For the electron excitation experiments, copper and tungsten targets were employed as X-ray sources, as they emit distinctive X-ray spectra upon electron beam bombardment. In the photon excitation experiments, a molybdenum target was used to produce a continuous spectrum with the prominent Mo Kα lines to emit pure copper and tungsten samples. TES detectors were used for the comparative spectroscopic analysis. The initial comparison revealed no substantial differences in the Kα and Kβ lines of copper across different excitation sources. Similarly, the Lα lines of tungsten exhibited uniformity under different excitation sources. However, this investigation revealed pronounced differences within the Lβ line series. The study found that XRF spectra preferentially excite outer-shell electrons, in contrast to intrinsic spectra, owing to different photon and electron interaction mechanisms. Photon interactions are selection-rule-dependent and involve a single electron, whereas electron interactions can involve multiple electrons without such limitations. This leads to varied excitation transitions, as evidenced in the observed Lβ line series.

This study presents a low-noise, high-rate front-end readout application-specific integrated circuit (ASIC) designed for the electromagnetic calorimeter (ECAL) of the Super Tau-Charm Facility (STCF). To address the high background-count rate in the STCF ECAL, the temporal features of signals are analyzed node-by-node along the chain of the analog front-end circuit. Then, the system is optimized to mitigate the pile-up effects and elevate the count rate to megahertz levels. First, a charge-sensitive amplifier (CSA) with a fast reset path is developed, enabling quick resetting when the output reaches the maximum amplitude. This prevents the CSA from entering a pulse-dead zone owing to amplifier saturation caused by the pile-up. Second, a high-order shaper with baseline holder circuits is improved to enhance the anti-pile-up capability while maintaining an effective noise-filtering performance. Third, a high-speed peak detection and hold circuit with an asynchronous first-input-first-output buffer function is proposed to hold and read the piled-up signals of the shaper. The ASIC is designed and manufactured using a standard commercial 1P6M 0.18 μm mixed-signal CMOS process with a chip area of 2.4 mm ×1.6 mm. The measurement results demonstrate a dynamic range of 4–500 fC with a nonlinearity error below 1.5%. For periodically distributed input signals, a count rate of 1.5 MHz/Ch is achieved with a peak time of 360 ns, resulting in an equivalent noise charge (ENC) of 2500 e^-. The maximum count rate is 4 MHz/Ch at a peak time of 120 ns. At a peak time of 1.68 μs with a 270 pF external capacitance, the minimum ENC is 1966 e^-, and the noise slope is 3.08 e^-/pF. The timing resolution is better than 125 ps at an input charge of 200 fC. The power consumption is 35 mW/Ch.

Meng Wang，Cen-Xi Yuan，Hong-Yi Wu，Guang-Xin Zhang，Yan-Yun Yang，Hao Jian，Xin-Xing Xu，Kai-Long Wang，Jia-Jian Liu，Chao-Yi Fu，Pengjie Li，Kang Wang，Fang-Fang Duan，Long-Hui Ru，Guang-Shun Li，Bing Ding，Yun-Hua Qiang，Jun-Bing Ma，Shi-Wei Xu，Yu-Feng Gao，Rui Fan，Fan-Chao Dai，Si-Xian Zha，Hao-Fan Zhu，Jin-Hai Li，Shu-Lian Qin，Zhi-Fang Chang，Cheng Kong，He-Xuan Yan，Hao-Wei Xu，Jia-Long Ning，Bo-Ren Liu，Jie Zhou，Yu-Dong Chen，Bo-Shuai Cai，Yu-Ting Wang，Zhi-Xuan Wang，Dong-Sheng Hou，Hu-Shan Xu，Xiao-Hong Zhou，Yu-Hu Zhang，Zheng-Guo Hu，Jenny Lee

A state-of-the-art detector array with a digital data acquisition system has been developed for charged-particle decay studies, including β-delayed protons, α decay, and direct proton emissions from exotic proton-rich nuclei. The digital data acquisition system enables precise synchronization and processing of complex signals from various detectors, such as plastic scintillators, silicon detectors, and germanium γ detectors. The system's performance was evaluated using the β decay of ³²Ar and its neighboring nuclei, produced via projectile fragmentation at the first Radioactive Ion Beam Line in Lanzhou (RIBLL1). Key measurements, including the half-life, charged-particle spectrum, and γ-ray spectrum, were obtained and compared with previous results for validation. Using the implantation-decay method, the isotopes of interest were implanted into two double-sided silicon strip detectors, where their subsequent decays were measured and correlated with preceding implantations using both position and time information. This detection system has potential for further applications, including the study of β-delayed charged-particle decay and direct proton emissions from even more exotic proton-rich nuclei.

In this study, the chemical freeze-out of hadrons, including light-and strange-flavor particles and light nuclei, produced in Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC), was investigated. Using the Thermal-FIST thermodynamic statistical model, we analyzed various particle sets: those inclusive of light nuclei, those exclusive to light nuclei, and those solely comprising light nuclei. We determined the chemical freeze-out parameters at sNN= 7.7–200 GeV and four different centralities. A significant finding was the decrease in the chemical freeze-out temperature T_ch with light nuclei inclusion, with an even more pronounced reduction when considering light nuclei yields exclusively. This suggests that light nuclei formation occurs at a later stage in the system's evolution at RHIC energies. We present parameterized formulas that describe the energy dependence of T_ch and the baryon chemical potential μ_B for three distinct particle sets in central Au+Au collisions at RHIC energies. Our results reveal at least three distinct T_ch at RHIC energies correspond to different freeze-out hypersurfaces: a light-flavor freeze-out temperature of T_L = 150.2±6 MeV, a strange-flavor freeze-out temperature T_s = 165.1±2.7 MeV, and a light-nuclei freeze-out temperature T_ln = 141.7±1.4 MeV. Notably, at the Large Hadron Collider (LHC) Pb+Pb 2.76 TeV, the expected lower freeze-out temperature for light nuclei was not observed; instead, the T_ch for light nuclei was found to be approximately 10 MeV higher than that for light-flavor hadrons.

The accurate photoneutron cross-section of the ²⁷Al nucleus has a significant impact on resolving differences in existing experimental data and enhancing the precision of nuclear reaction rate calculations for ²⁶Al in nuclear astrophysics. The photoneutron cross-sections for the ²⁷Al(γ, n)²⁶Al reaction, within the neutron separation energy range of 13.2–21.7 MeV, were meticulously measured using a new flat efficiency detector (FED) array at the Shanghai Laser-Electron Gamma Source (SLEGS). The uncertainty of the data was controlled to below 4% throughout the process, and inconsistencies between the present data and existing data from different gamma sources, as well as the TENDL-2021 data, are discussed in detail. These discussions provide a valuable reference for addressing discrepancies in the ²⁷Al(γ, n)²⁶Al cross-section data and improving related theoretical calculations.

A half-size prototype of the multi-wire drift chamber (MWDC) for the cooling storage ring (CSR) external target experiment (CEE) was assembled and tested in the 350 MeV/u Kr+Fe reactions at the heavy-ion research facility in Lanzhou (HIRFL). The prototype consists of six sense layers, where the sense wires are stretched in three directions X, U, and V; meeting 0°, 30°, and -30°, respectively, with respect to the vertical axis. The sensitive area of the prototype is 76 cm × 76 cm. The amplified and shaped signals from the anode wires were digitized in a serial capacity array. When operating at a high voltage of 1500 V on the anode wires, the efficiency for each layer is greater than 95%. The tracking residual is approximately 301 ± 2 μm. This performance satisfies the requirements of CEE.

In this study, we explore the impact of state-of-the-art laser fields on the α decay half-life of deformed ground-state odd-A nuclei within the proton number range of 52–107. The calculations show that the presence of a laser field modulates the α decay half-life by altering the α decay penetration probability within a limited range. Moreover, the variance in the penetration probability rate of change between even-odd and odd-even nuclei is investigated. Furthermore, we investigate the rate of change of the penetration probability for the same parent nucleus with different neutron numbers, based on the characteristics of the odd-A nucleus. We found that the influence of the laser field on the penetration probability is determined by both the shell effect and odd-even staggering. This research contributes to the understanding of nuanced interactions between laser fields and nuclear decay processes. Therefore, valuable insights for future experiments in laser-nuclear physics are attainable using this study.

Grating-based X-ray phase-contrast imaging enhances the contrast of imaged objects, particularly soft tissues. However, the radiation dose in computed tomography (CT) is generally excessive owing to the complex collection scheme. Sparse-view CT collection reduces the radiation dose, but with reduced resolution and reconstructed artifacts particularly in analytical reconstruction methods. Recently, deep learning has been employed in sparse-view CT reconstruction and achieved state-of-the-art results. Nevertheless, its low generalization performance and requirement for abundant training datasets have hindered the practical application of deep learning in phase-contrast CT. In this study, a CT model was used to generate a substantial number of simulated training datasets, thereby circumventing the need for experimental datasets. By training a network with simulated training datasets, the proposed method achieves high generalization performance in attenuation-based CT and phase-contrast CT, despite the lack of sufficient experimental datasets. In experiments utilizing only half of the CT data, our proposed method obtained an image quality comparable to that of the filtered back-projection algorithm with full-view projection. The proposed method simultaneously addresses two challenges in phase-contrast three-dimensional imaging, namely, the lack of experimental datasets and the high exposure dose, through model-driven deep learning. This method significantly accelerates the practical application of phase-contrast CT.