Vol.34,

This study presents an electronics system for cosmic X-ray polarization detection (CXPD). The CXPD was designed as a high-sensitivity soft X-ray polarimeter with a measurement energy range of 2–10 keV carried by a CubeSat. A Stable and functionally complete electronics system under power and space constraints is a key challenge. The complete CXPD electronics system (CXPDES) comprises hardware and firmware. CXPDES adopts a three-layer electronic board structure based on functionality and available space. Two gas pixel detectors (GPDs) were placed on the top layer board and CXPDES provided the GPDs with voltages up to -4000 V. Each GPD signal was digitized, compressed, encoded, and stored before being transmitted to the ground. The CXPDES provided stable and high-speed communication based on a scheme that separated command and data transmission and it supports the CXPDES in-orbit upgrade. In addition, environmental monitors, silicon photomultiplier (SiPM) triggers, power management, GPDs configuration, and mode switches were included in the overall operating logic of the CXPDES. The results obtained by testing the CXPDES showed that it satisfied all the requirements of CXPD. The CXPDES provides design experience and technological readiness for future large-area X-ray polarimetry missions.

471

To improve the efficiency and accuracy of single- event effect (SEE) research at the Heavy Ion Research Facility at Lanzhou (HIRFL), Hi’Beam-SEE must precisely localize the position at which each heavy ion hitting the integrated circuit (IC) causes SEE. In this study, we propose a fast multi-track location (FML) method based on deep learning to locate the position of each particle track with high speed and accuracy. FML can process a vast amount of data supplied by Hi’Beam-SEE on-line, revealing sensitive areas in real time. FML is a slot-based object-centric encoder-decoder structure in which each slot can learn the location information of each track in the image. To make the method more accurate for real data, we designed an algorithm to generate a simulated dataset with a distribution similar to that of the real data, which was then used to train the model. Extensive comparison experiments demonstrated that the FML method, which has the best performance on simulated datasets, has high accuracy on real datasets as well. In particular, FML can reach 238 fps and a standard error of 1.6237 μm. This study discusses the design and performance of FML.

469

An in-depth understanding of the structure-activity relationship between the surface structure, chemical composition, adsorption and desorption of molecules, and their reaction activity and selectivity is necessary for the rational design of high-performance catalysts. Herein, we present a method for studying catalytic mechanisms using a combination of in situ reaction cells and surface science techniques. The proposed system consists of four parts: preparation chamber, temperature-programmed desorption (TPD) chamber, quick load-lock chamber, and in situ reaction cell. The preparation chamber was equipped with setups based on the surface science techniques used for standard sample preparation and characterization, including an Ar⁺ sputter gun, Auger electron spectrometer, and a low-energy electron diffractometer. After a well-defined model catalyst was prepared, the sample was transferred to a TPD chamber to investigate the adsorption and desorption of the probe molecule, or to the reaction cell, to measure the catalytic activity. A thermal desorption experiment for methanol on a clean Cu(111) surface was conducted to demonstrate the functionality of the preparation and TPD chambers. Moreover, the repeatability of the in situ reaction cell experiment was verified by CO₂ hydrogenation on the Ni(110) surface. At a reaction pressure of 800 Torr at 673 K, turnover frequencies for the methanation reaction and reverse water-gas shift (RWGS) reaction were 0.15 and 7.55 Ni atom^-1s^-1, respectively.

451

X-ray imaging technologies such as digital radiography (DR), is an important aspect of modern non-destructive testing (NDT) and medical diagnosis. Innovative flexible X-ray detector technologies have recently been proposed and are now receiving increasing attention owing to their superior material flexibility compared with traditional flat-panel detectors. This work aims to study these innovative flexible X-ray detectors in terms of their effectiveness in DR imaging, such as detection efficiency and spatial resolution. To achieve this goal, first, a Monte Carlo model was developed and calibrated to an in-lab 150 kV DR imaging system containing a flat-panel X-ray detector. Second, the validated model was updated with various types of flexible X-ray detectors to assess their performance in nearly realistic conditions. Key parameters such as the detection efficiency pertaining to the crystal material and thickness were studied and analyzed across a broader energy range up to 662 keV. Finally, the imaging performance of the different detectors was evaluated and compared to that of the flat-panel detector in the 150 kV DR imaging system. The results show that the flexible detectors such as the CsPbBr₃ crystal detector deliver promising performance in X-ray imaging and can be applied to a wider range of application scenarios, especially those requiring accurate detection at challenging angles.

571

The development of a detuning system for the precision control of electron energy is a major challenge when electron targets are used in ion-storage rings. Thus, a high-precision, high-voltage, detuning system was developed for the electron target of a high-intensity heavy-ion accelerator facility-spectrometer ring (HIAF-SRing) to produce accurate electron-ion relative energies during experiments. The system consists of auxiliary, and high-voltage detuning power supplies. The front stage of the auxiliary power supply adopts an LCC resonant converter operating in the soft-switching state and an LC filter for a sinusoidal waveform output in the post-stage. The detuning power supply is a high-voltage pulse amplifier (HVPA) connected with a high-voltage DC (HVDC) module in series. In this paper, the design and development of the detuning system are described in detail, and the test bench is presented. The test results demonstrated that the detuning system conforms to the technical specifications of the dielectronic recombination (DR) experiment. Finally, a Fe¹⁵⁺ DR spectrum was measured using the detuning system. The experimental data demonstrated a good experimental resolution and verified the reliability and feasibility of the design.

441

Owing to the immobility of traditional reactors and spallation neutron sources, the demand for compact thermal neutron radiography (CTNR) based on accelerator neutron sources has rapidly increased in industrial applications. Recently, thermal neutron radiography experiments based on a D-T neutron generator performed by Hefei Institutes of Physical Science indicated a significant resolution deviation between the experimental results and the values calculated using the traditional resolution model. The experimental result was up to 23% lower than the calculated result, which hinders the achievement of the design goal of a compact neutron radiography system. A GEANT4 Monte Carlo code was developed to simulate the CTNR process, aiming to identify the key factors leading to resolution deviation. The effects of a low collimation ratio and high-energy neutrons were analyzed based on the neutron beam environment of the CTNR system. The results showed that the deviation was primarily caused by geometric distortion at low collimation ratios and radiation noise induced by high-energy neutrons. Additionally, the theoretical model was modified by considering the imaging position and radiation noise factors. The modified theoretical model was in good agreement with the experimental results, and the maximum deviation was reduced to 4.22%. This can be useful for the high-precision design of CTNR systems.

617

A simulation code, GOAT, is developed to simulate single-bunch intensity-dependent effects and their interplay in the proton ring (pRing) of the Electron-Ion Collider in China (EicC) project. GOAT is a scalable and portable macroparticle tracking code written in Python and coded by object-oriented programming technology. It allows for transverse and longitudinal tracking, including impedance, space charge effect, electron cloud effect, and beam-beam interaction. In this paper, physical models and numerical approaches for the four types of high-intensity effects, together with the benchmark results obtained through other simulation codes or theories, are presented and discussed. In addition, a numerical application of the cross-talk simulation between the beam-beam interaction and transverse impedance is shown, and a dipole instability is observed below the respective instability threshold. Different mitigation measures implemented in the code are used to suppress the instability. The flexibility, completeness, and advancement demonstrate that GOAT is a powerful tool for beam dynamics studies in the EicC project or other high-intensity accelerators.

451

The introduction of metals into vitreous matrices is the origin of various interesting phenomena; in particular, the presence of copper ions in glass has been the subject of considerable research because of its numerous applications. The ion-exchange process is primarily used to introduce copper ions into glass matrices. The thermoluminescence (TL) of silicate glass was studied to evaluate its potential as gamma-sensitive material for dosimetric applications; the effect of copper doping on the thermoluminescent sensitivity was investigated using the Cu-Na ion-exchange technique for different concentrations and doping conditions, over a wide dose range of 10 mGy to 100 kGy. The results showed that Cu doping significantly improved the sensitivity of the glasses to gamma radiation. After the ion-exchange, two peaks appeared in the glow curves at approximately 175 and 230 ℃, respectively, which possibly originated from the Cu⁺ centers, along with a weak TL peak at around 320 ℃. We also attempted to explain the origin of the observed thermoluminescence by exploiting the Electron paramagnetic resonance (EPR) spectra. The results clearly show quenching of the TL emission with increasing copper concentrations. The present work indicates that the thermoluminescence response of these glasses to gamma rays can be reasonably measured in the range of 0.001–100 kGy. This study also facilitates the understanding of the basic TL mechanism in this glass system.

612

Silver nanoclusters (AgNCs) are a new type of nanomaterials with similar properties to molecules and unique applications. The applications of AgNCs can be significantly expanded by combining them with different matrix materials to obtain AgNC composites. Using irradiation techniques, we developed a simple two-step method for preparing silver nanocluster composites. First, polyacrylic acid (PAA) chains were grafted onto the surface of a PE film as templates (PE-g-PAA). Subsequently, silver ions were reduced in situ on the surface of the template material to obtain the AgNC composites (AgNCs@PE-g-PAA). The degree of AgNC loading on the composite film was easily controlled by adjusting the reaction conditions. The loaded AgNCs were anchored to the carboxyl groups of the PAA and wrapped in the graft chain. The particle size of the AgNCs was only 4.38±0.85 nm, with a very uniform particle size distribution. The AgNCs@PE-g-PAA exhibited fluorescence characteristics derived from the AgNCs. The fluorescence of the AgNCs@PE-g-PAA was easily quenched by Cr³⁺ ions. The composite can be used as a fluorescence test paper to realize visual detection of Cr³⁺.

407

The thermal diffusion column represents one method of separating stable isotopes. This method is advantageous for small-scale operations because of the simplicity of the apparatus and small inventory, especially in gas-phase operations. Consequently, it has attracted attention for its applicability in tritium and noble gas separation systems. In this study, the R cascade was used to design and determine the number of columns. A square cascade was adopted for the final design because of its flexibility, and calculations were performed to separate ²⁰Ne and ²²Ne isotopes. All the R cascades that enriched the Ne isotopes by more than 99% were investigated, the number of columns was determined, and the square cascade parameters were optimized using the specified columns. Additionally, a calculation code ''RSQ_CASCADE'' was developed. A unit separation factor of three was considered, and the number of studied stages ranged from 10 to 20. The results showed that the column separation power, relative total flow rate, and required number of columns were linearly related to the number of stages. The separation power and relative total flow decreased and the number of columns increased as the stage number increased. Therefore, a cascade of 85 columns is recommended to separate the stable Ne isotopes. These calculations yielded a 17-stage square cascade with five columns in each stage. By changing the stage cut, feed point, and cascade feed flow rate, the best parameters for the square cascade were determined according to the cascade and column separation powers. As the column separation power had a maximum value in cascade feed 50, it was selected for separating Ne isotopes.

344

To provide a reliable and comprehensive data reference for core geometry design of graphite-moderated and low-enriched uranium fueled molten salt reactors, the influences of geometric parameters on the temperature coefficient of reactivity (TCR) at an assembly level were characterized. A four-factor formula was introduced to explain how different reactivity coefficients behave in terms of the fuel salt volume fraction and assembly size. The results show that the fuel salt temperature coefficient (FSTC) is always negative owing to a more negative fuel salt density coefficient in the over-moderated region or a more negative Doppler coefficient in the under-moderated region. Depending on the fuel salt channel spacing, the graphite moderator temperature coefficient (MTC) can be negative or positive. Furthermore, an assembly with a smaller fuel salt channel spacing is more likely to exhibit a negative MTC. As the fuel salt volume fraction increases, the negative FSTC first weakens and then increases, owing to the fuel salt density effect gradually weakening from negative to positive feedback and then decreasing. Meanwhile, the MTC weakens as the thermal utilization coefficient caused by the graphite temperature effect deteriorates. Thus, the negative TCR first weakens and then strengthens, mainly because of the change in the fuel salt density coefficient. As the assembly size increases, the magnitude of the FSTC decreases monotonously owing to a monotonously weakened fuel salt Doppler coefficient, whereas the MTC changes from gradually weakened negative feedback to gradually enhanced positive feedback. Then, the negative TCR weakens. Therefore, to achieve a proper negative TCR, particularly a negative MTC, an assembly with a smaller fuel salt channel spacing in the under-moderated region is strongly recommended.

456

In recent years, Graphics Processing Units (GPUs) have been applied to accelerate Monte Carlo (MC) simulations for proton dose calculation in radiotherapy. Nonetheless, current GPU platforms, such as Compute Unified Device Architecture (CUDA) and Open Computing Language (OpenCL), suffer from cross-platform limitation or relatively high programming barrier. However, the Taichi toolkit, which was developed to overcome these difficulties, has been successfully applied to high-performance numerical computations. Based on the class II condensed history simulation scheme with various proton-nucleus interactions, we developed a GPU-accelerated MC engine for proton transport using the Taichi toolkit. Dose distributions in homogeneous and heterogeneous geometries were calculated for 110, 160, and 200 MeV protons and were compared with those obtained by full MC simulations using TOPAS. The gamma passing rates were greater than 0.99 and 0.95 with criteria of 2 mm, 2% and 1 mm, 1%, respectively, in all the benchmark tests. Moreover, the calculation speed was at least 5800 times faster than that of TOPAS, and the number of lines of code was approximately 10 times lesser than those of CUDA or OpenCL. Our study provides a highly accurate, efficient, and easy-to-use proton dose calculation engine for fast prototyping, beamlet calculation, and education purposes.

553

Recent reactor antineutrino experiments have observed that the neutrino spectrum changes with the reactor core evolution and that the individual fissile isotope antineutrino spectra can be decomposed from the evolving data, providing valuable information for the reactor model and data inconsistent problems. We propose a machine learning method by building a convolutional neural network based on a virtual experiment with a typical short-baseline reactor antineutrino experiment configuration: by utilizing the reactor evolution information, the major fissile isotope spectra are correctly extracted, and the uncertainties are evaluated using the Monte Carlo method. Validation tests show that the method is unbiased and introduces tiny extra uncertainties.

448

In this study, we theoretically investigate the feasibility of using laser-wakefield accelerated (LWFA) electrons for the photonuclear measurement of nuclear isomers according to the characteristics of the electrons obtained from LWFA experiments conducted at the Compact Laser Plasma Accelerator (CLAPA) laboratory. The experiments at the CLAPA show that a stable electron beam with an energy of 78–135 MeV and a charge of 300-600 pC can be obtained. The bremsstrahlung spectra were simulated using Geant4, which suggests that a bremsstrahlung source with a peak intensity of 10¹⁹ photons/s can be generated. Theoretical calculations of isomer production cross-sections from the photonuclear reactions on six target nuclei, ¹⁹⁷Au, ¹⁸⁰Hf, ¹⁵⁹Tb, ¹¹⁵In, ¹⁰³Rh, and ⁹⁰Zr were performed and compared with the available experimental data in EXFOR, which suggest that further experiments are required for a series of photonuclear reaction channels. Flux-averaged cross sections and isomer ratios (IR) resulting from such bremsstrahlung sources are theoretically deduced. The results suggest that IR measurements can be used to constrain nuclear components, such as γ strength function and optical model potential. In addition, the detection of the decay characteristics was evaluated with Geant4 simulations. The use of the LWFA electron beam and its bremsstrahlung for photonuclear studies involving nuclear isomers is anticipated.

555

Density fluctuations and correlations due to a first-order quark-gluon plasma to hadronic matter phase transition and its critical end point, if they remain present after the hadronic evolution in a heavy ion collisions, can lead to an enhanced production of light nuclei in these collisions. This would then result in a non-monotonic collision energy dependence of the yield ratio NtNp/Nd2 of proton number N_p, deuteron number N_d, and triton number N_t. Measurements of this yield ratio as a function of collision energy thus provides the possibility to probe the equation of state of strong-interaction matter and its phase diagram.

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