分类: 物理学 >> 核物理学 提交时间: 2025-06-30
摘要: A new multi-detector array named HALIMA (Hybrid Array for LIfetime MeAsurement) has been developed at Lanzhou, for nuclear structure studies in fission. The array comprises eight BGO-shielded High-Purity Germanium (HPGe) detectors and twenty fast Ce-doped Lanthanum Bromide [LaBr3(Ce)] detectors shielded with CsI(Tl). HALIMA is further complemented by two ancillary detector systems: fission fragment (FF) detectors and β detectors. This configuration enables precise sub-nanosecond lifetime measurements using a four-fold FF/β-Ge-LaBr3(Ce)-LaBr3(Ce) coincidence technique. The performance and specifications of the detectors, associated electronics, and data acquisition system are presented in detail. The advantage of FF selectivity is emphasized, which significantly enhances the sensitivity to specific fission channels. Using this approach, lifetimes of nuclear excited states populated in the spontaneous fission of 252Cf have been measured, showing good agreement with established literature values.
分类: 物理学 >> 核物理学 提交时间: 2025-06-14
摘要: For the prompt monitoring of radionuclides released into the atmosphere by various nuclear facilities and sudden nuclear accidents, a nonsampling atmospheric radionuclide online measurement system (NSAROMS) that is based on NaI(Tl) scintillators was developed. Compared with traditional measurement methods, this online system eliminates the enrichment sampling process. The selection of the detector, the design of the ground gamma-ray shielding device, and the detection efficiency of the measurement system were simulated using Monte Carlo simulation. A calibration experiment was subsequently carried out to measure the detection efficiency of the system, and the relative error between the detection efficiency obtained by calibration and the detection efficiency obtained by Monte Carlo simulation was within 5%. The minimum detectable activity concentrations (MDACs) for several common atmospheric radionuclides, including ²¹⁴Pb, ²¹⁴Bi, ⁷Be, ²²Na, ¹³⁴Cs, ¹³⁷Cs, ¹³¹I, and ⁴⁰K, were calculated on the basis of the measured detection efficiencies for a system measurement duration of 30 minutes. Finally, preliminary applications were carried out in Mianyang, Leshan, Yibin, and Guangyuan, with measured average atmospheric radon concentrations of 7.87 ± 0.23 Bq/m³, 4.48 ± 0.15 Bq/m³, 4.30 ± 0.13 Bq/m³, and 9.90 ± 0.29 Bq/m³, respectively. The NSAROMS meets the requirements for monitoring atmospheric radionuclides in nuclear facilities. It can accurately measure the activity concentrations of radionuclides in the atmosphere and offers advantages such as convenience, a wide measurement range, low detection limits, and the ability to perform onsite online measurements at nuclear facilities.
分类: 物理学 >> 核物理学 提交时间: 2025-06-04
摘要: Cs2LiYCl6: Ce (CLYC) scintillator is sensitive to neutrons within a wide-energy range and has the potential to achieve wide-range neutron energy spectrum measurements. The direct neutron detection performance of a CLYC detector has been realized by utilizing the Back-n white neutron source at China Spallation Neutron Source (CSNS), where a 20 cm lead brick was designed to effectively shield the accompanying gamma flash from the neutron source. The detected neutron energy spectrum after passing through the lead brick is primarily distributed within the 0.1–300 MeV and exhibits identical four-peak structures, which are consistent with Geant4 simulation results. The peak energies of the 1st, 3rd, and 4th peaks match well, with the relative deviation being less than 6%. However, a large energy deviation has been found for the 2nd peak whose energy falls within the resonance energy region of lead, which indicates that the resonance reaction of lead might not be precisely simulated in Geant4. Due to the dominance of elastic scattering between neutrons and the main nuclides (6Li, 35Cl, 37Cl, 89Y, 133Cs, 140Ce) in the CLYC scintillator in the low-energy region, suppression has been found for reactions that are used for neutron detection reactions such as (n, p), (n, d), (n, t) and (n, α). This leads to a significant difference in overall intensity between the low-energy range within 0.1–3 MeV (1st and 2nd peaks) and the high-energy range within 5–64 MeV (3rd and 4th peaks). A large number of gamma signals were measured in the experiment, which were found to be prompt gamma rays generated from neutron reactions with CLYC, but not the associated gamma rays from the neutron source. This phenomenon is more pronounced for the high-energy region, these prompt gamma rays can be combined into the neutron pulses and render the neutron pulses to contain fast-decay components that originally only existed in gamma pulses, and further decrease the neutron gamma discrimination performance of CLYC. By establishing a wide-energy neutron response matrix entirely based on experimental measurements and utilizing the GRAVEL unfolding method, the white neutron energy spectrum in the range of 6–200 MeV was successfully unfolded. These results provide a critical reference for the accurate measurement and discrimination of neutron-gamma signals in radiation fields using CLYC detectors and indicate the feasibility of using CLYC detectors for wide-energy neutron spectrum measurements, highlighting its potential for applications in high-energy neutron experiments, space neutron detection, and other related fields.
分类: 物理学 >> 核物理学 提交时间: 2025-05-17
摘要: This study focuses on the Pellet-Cladding Mechanical Interaction (PCI) behavior of silicon carbide fiber-reinforced silicon carbide composite (SiCf/SiC) cladding as an Accident-Tolerant Fuel (ATF) material. A specialized mandrel expansion test apparatus was developed to systematically investigate its failure characteristics under ambient and elevated temperatures (up to 920°C) and varied loading rates (0.5–1 mm/min). The experimental setup integrated Digital Image Correlation (DIC) and strain gauge systems to quantify stress-strain responses and critical failure parameters. Results demonstrated that elevated temperatures significantly degraded the load-bearing capacity of SiCf/SiC cladding, with average failure loads decreasing by 36.7% and failure strains reducing by 9.8%. Increased loading rates exacerbated non-uniform plastic deformation, leading to approximately 30% lower failure loads under room-temperature conditions. Furthermore, the failure process of SiCf/SiC cladding exhibited five distinct stages, with Stage IV (plunger-induced radial compression triggering cladding rupture) identified as the critical failure phase. This research provides essential experimental data for evaluating PCI performance of SiCf/SiC composite cladding, elucidates its high-temperature mechanical degradation mechanisms, and offers theoretical insights for optimizing nuclear fuel element design.
分类: 物理学 >> 核物理学 提交时间: 2025-05-06
摘要: The technique of Bρ-defined isochronous mass spectrometry (Bρ-IMS), established at a storage ring, serves as a valuable tool for determining the masses of short-lived nuclei. In the previous Bρ-IMS experiments, the effects of magnetic field drifts have to be corrected in order to improve the mass resolving power of Bρ-IMS [Eur. Phys. J. A 59, 27 (2023)]. The correction procedures are complicated and require multiple reference ions with well-known masses in each injection, which may not be the cases in the measurements of exotic nuclei with tiny production yields. In this study, we propose a novel approach of Bρ-IMS that requires only one reference ion for mass determination in an individual injection, avoiding the tedious and complicated correction procedures. This approach achieves the mass precision comparable to that of previous Bρ-IMS results, and is approved to be suitable for future mass measurements of exotic nuclei with extremely low production yields.
分类: 物理学 >> 核物理学 提交时间: 2025-04-19
摘要: Background The well-type NaI(Tl) detector, a conventional 4πγ counting system, facilitates rapid sample screening but is constrained by efficiency calibration dependencies on standard sources and suboptimal geometric configurations. These limitations hinder measurements of irregularly shaped or difficult-to-prepare radioactive sources and necessitate efficiency corrections for cascade γ-emitting nuclides. Objective This work addresses these challenges by integrating Monte Carlo (MI)-simulated efficiency calibration with an optimized detector design. Method & Results Geant4 simulations determined the optimal well depth (85 mm for Φ20 mm diameter within a Φ150×150 mm crystal) by analyzing efficiency curves of 14 nuclides and 31 mono-energetic γ-rays. Post-fabrication tests using a 137Cs standard source validated critical performance metrics: background count rate (nb=109.7 s-1), energy resolution (RE=9.4% @ 661.7 keV), and 12-hour stability (δ<1.5%). Activity determinations for six nuclides (18F, 22Na, 68Ge-68Ga, 133Ba, 64Cu, 198Au) exhibited agreement (|En|<1) with 4πβ-γ coincidence and TDCR-LSC reference values. Conclusion The geometric optimization based on MC simulation made the detector close to the theoretical optimal configuration and reduced the uncertainty of efficiency correction while achieving relative expanded uncertainty Urel<2.0% (k=2), improving the work efficiency of radioactive source activity measurement. The reliability of the model was confirmed by measurement and comparison, and it can be used to simulate the detection efficiency of difficult to prepare or irregular radioactive sources, and provide reference for related research.
分类: 核科学技术 >> 核科学与技术 提交时间: 2025-03-28
摘要: Efficiency calibration is a critical step that enables the conversion of the detectors’ count rate into the activityof radionuclides in the examined parts for in vivo measurement. However, to date, there hasn’t been awell-accepted framework for efficiency calibration. As such, it is often found researchers employ various kindsof anthropomorphic phantoms with considerably different patterns of radionuclide distribution coupling withdrastically different numbers of detectors to derive the calibration factor, rendering the cross-comparison amongstudies challenging. Moreover, some studies employ virtual calibration, whereas others prefer experimental calibration,though their equivalency has not been fully explored. In this paper, focusing on in vivo measurement ofPb-210 in the skull, a promising technique for individualized reconstruction of radon exposure is presented, anda detailed framework for efficiency calibration covering key issues mentioned above is provided. To be specific,physical phantoms of Pb-210 in the skull are developed based on the anatomical characteristics of a Chineseadult reference male, along with the corresponding computational phantoms constructed from computed tomographyscan. In comparison, the average deviations between simulation and experimental results are within 4%for efficiency calibration at the top, left, and right sides of the head across varying detection distances. Furthermore,based on the investigation of Pb-210 distribution regions reported in literature, the calculation methodfor Pb-210 activity is improved to account for different source distributions and joint measurements with multipledetectors. The results are useful for determining the appropriate conversion procedure under differentmeasurement conditions.
分类: 物理学 >> 核物理学 提交时间: 2025-03-10
摘要: A new detector array with a large solid angle coverage for coincidence measurement of charged fragments was developed to study the breakup reaction mechanisms of weakly bound nuclear systems at energies around the Coulomb barrier. The array has been used for exploring the breakup reaction mechanisms of 6,7Li + 209Bi systems at Ebeam = 30, 40, 47 MeV, showing good performances of particle identification and complete kinematic measurements. Based on this, different breakup modes are distinguished clearly and some new breakup modes are discovered, such as 7Li → α+ t breakup mode in 6Li + 209Bi system and 7Li → 6He + p breakup mode in 7Li + 209Bi system. It is shown that this array can be also used to explore other breakup reaction mechanisms induced by weakly bound nuclei.
分类: 物理学 >> 核物理学 提交时间: 2025-03-10
摘要: This paper presents a technique for extracting the initial parameters of the longitudinal phase space of freshly injected bunches in an electron storage ring. This technique combines the development of a single-bunch injection phase space simulation software with the establishment of a bunch-by-bunch data acquisition and processing system, enabling high-precision acquisition of the initial parameters of injected bunches during the injection process into the electron storage ring (including initial phase, initial bunch length, initial energy offset, initial energy spread, and initial energy chirp). The experiment utilizes a high-speed oscilloscope to capture the beam injection signals, which are then processed by a data processing script to calculate and extract the phase and bunch length evolution information of the injected bunches. The data acquisition length covers several thousand turns per capture, with a phase measurement accuracy of 0.2 ps and a bunch length measurement accuracy of 1 ps. Additionally, a single-bunch simulation software based on the mbtrack2 and PyQt5 packages has been developed. This software can simulate the phase space evolution of bunches under different initial conditions after injection. By employing a genetic algorithm and integrating experimental data with simulation data, it can obtain the optimized initial parameters of the injected bunches.
分类: 物理学 >> 核物理学 提交时间: 2025-01-27
摘要: The X-ray fluorescence (XRF) system is designed and developed to enable faster and more convenient material composition detection and analysis. The system includes a Si-PIN detector, readout electronics, and a host computer. An algorithm is designed so that the detector can be used without vacuum and the device can achieve online composition analysis and data transmission. Testing was conducted using an iron ore sample, and the results demonstrate that the device achieves an energy resolution of 7.35% @6.4 keV. The measured result shows an 8% error compared to chemical methods. The device is capable of rapid composition analysis, with the potential for further applications in fields such as nuclear physics and mineral detection for industrial use.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2024-10-29
摘要: Schottky mass spectrometry utilizing heavy-ion storage rings is a powerful technique for the precise mass and decay half-life measurements of highly charged ions. Owing to the non-destructive ion-detection features of Schottky noise detectors, the number of stored ions in the ring is determined by the peak area in the measured revolution-frequency spectrum. Because of their intrinsic amplitude-frequency characteristic (AFC), Schottky detector systems exhibit varying sensitivities at different frequencies. Using low-energy electron-cooled stored ions, a new method is developed to calibrate the AFC curve of the Schottky detector system of the Cooler Storage Ring (CSRe) storage ring located in Lanzhou, China. Using the amplitude-calibrated frequency spectrum, a notable refinement was observed in the precision of both the peak position and peak area. As a result, the storage lifetimes of the electron-cooled fully-ionized 56Fe26+ ions were determined with high precision at beam energies of 13.7 and 116.4 MeV/u, despite of frequency drifts during the experiment. When electron cooling was turned off, the effective vacuum condition experienced by the 116.4 MeV/u 56Fe26+ ions was determined using amplitude-calibrated spectra, revealing a value of 2×10−10 mbar, which is consistent with vacuum-gauge readings along the CSRe ring. The method reported herein will be adapted for the next-generation storage ring of the HIAF facility under construction in Huizhou, China. It can also be adapted to other storage-ring facilities worldwide to improve precision and enhance lifetime measurements using many ions in the ring.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2024-10-29
摘要: Burnup measurement is crucial for the management and disposal of spent fuel. The conventional approachindirectly estimates burnup by examining the fission product or actinide content. Compared to the first twomethods, the active neutron method exhibit a lower dependence on the irradiation history and initial enrichmentdegree of the spent fuel. In addition, it can be used to directly determine the content of fissile nuclides in spentfuel. This study proposed the design of a burnup measurement equipment specifically crafted for plate segmentsby utilizing a compact D-D neutron generator. The equipment initiates the fission of fissile nuclides within thespent fuel plate segment through thermal neutrons provided by the moderators. Subsequently, the burnup isdetermined by analyzing the transmitted thermal neutrons and counting the fission fast neutrons. The MonteCarlo program Geant4 was used to simulate the relationship between spent fuel plate segment assembly burnupand the detector count of 10MW material test reactor designed by the International Atomic Energy Agency.Consequently, the feasibility of the method and rationality of the detector design were verified.
分类: 物理学 >> 核物理学 提交时间: 2024-09-24
摘要: In order to accurately reconstruct the TGS transmission measurement image, this paper optimized the trans#2;mission reconstruction equation according to the actual situation of TGS transmission measurement. Based on the transmission reconstruction equation and the Monte Carlo program Geant4, an innovative virtual trajectory length model was devised. This model integrated the solving process of trajectory length and detection efficiency within a same model. To mitigate the influence of the angular distribution of γ-rays emitted by the transmitted source at the detector, the transport processes of numerous particles traversing a virtual nuclear waste barrel with a density of 0 were simulated, and some information at each step of the particle transport were captured. Simultaneously, the model addressed the non-uniform detection efficiency of the detector end face by considering whether the energy deposition of particles in the detector equals their initial energy. Two models were established to validate the accuracy and reliability of the virtual trajectory length model: Model 1, a simplified nuclear waste barrel, and Model 2, which closely resembled the actual structure of a nuclear waste barrel. Research results indicated that the proposed virtual trajectory length model significantly enhanced the precision of trajectory length determination, substantially elevating the quality of reconstructed images. For example, comparing the reconstructed images of Model 2 using the "point-to-point" model and the average trajectory model, the SNR increased by 375.0% and 112.7%, respectively. Consequently, the virtual trajectory length model proposed in this paper holds paramount significance for the precise reconstruction of transmission images, and can provide support for accurate detection of radioactive activity in nuclear waste barrels.
分类: 物理学 >> 核物理学 提交时间: 2024-09-13
摘要: In conventional isochronous mass spectrometry (IMS) performed at a storage ring, the precision of mass measurement for short-lived nuclei depends on the precise determination of the revolution times (Ts) of stored ions. However, the resolution of T inevitably deteriorates due to the magnetic rigidity spread of the ions, resulting in limited mass resolving power. In this work, we measure the betatron tune Q (the number of betatron oscillations within a single revolution) of the ions, and construct a correlation between T and Q. From this correlation, the T are transformed corresponding to a fixed Q with higher resolution. Using the transformed Ts, we re-determine the masses of 63Ge, 65As, 67Se, and 71Kr, which agree well with the mass values measured by the newly developed IMS (Bρ-IMS). We also study the systematics of Coulomb displacement energies (CDEs) and find that the anomalous staggering in CDEs is removed using the new mass values. This method of T transformation is very useful for the conventional IMS equipped with a single time-of-flight detector.
分类: 物理学 >> 核物理学 提交时间: 2024-08-31
摘要: Schottky mass spectrometry utilizing heavy-ion storage rings serves as a powerful technique for precision mass and decay half-life measurements of highly charged ions. The number of stored ions in the ring is determined by the peak area in the revolution frequency spectrum. Due to intrinsic amplitude frequency characteristic (AFC), Schottky detector systems exhibit varying sensitivities at different frequencies. In this paper, a new method was developed in order to calibrate the AFC curve of the Schottky detector system of the CSRe storage ring using low-energy electron-cooled stored ions. With the amplitude-calibrated frequency spectrum, there was a notable refinement in the precision of both the peak position and peak area. As a result, the storage lifetimesof the electron-cooled fully-ionized 56Fe26+ ions were determined with high precision at the beam energy of 13.7 MeV/u and 116.4 MeV/u, despite of frequency drifts during the experiment. When the electron cooling is turned off, the effective vacuum condition experienced by the 116.4 MeV/u 56Fe26+ ions was determined using the amplitude-calibrated spectra, revealing a value of 10−10 mbar which is consistent with the vacuum gauges readings along the CSRe ring. The method reported here can be adapted at other storage ring facilities to improve the precision and enhance the capability of life-time measurement in the ring.
分类: 管理学 >> 管理学其他学科 提交时间: 2024-06-13
摘要: Abstract:Public toilets reflect human civilization, embodying not only social efficiency but also gender equality. However, the current widespread issue of insufficient and mismatched toilet spaces persists. The demand for toilet facilities by men and women is not simply a matter of population ratios. Due to differences in wait times, arrival time distributions, and the ability for men to switch to urinals, the traditional queuing theory is not precise enough for this issue. This study investigates the usage of public toilets and constructs a simulation system based on agent-based modeling. Using this system, the toilet space requirements for gender-segregated and non-segregated toilets are measured under different satisfaction rates, foot traffic volumes, and toilet usage frequencies. Additionally, the consistency between the real distribution of time spent entering and exiting toilets and the simulation system is verified, demonstrating the robustness of the conclusions drawn. The study concludes that under a fixed satisfaction rate, the number of toilet stalls satisfies a specific function of foot traffic volume. The agent-based modeling approach demonstrated in this study can be extended to address other complex real-world optimization problems.
分类: 天文学 >> 天文仪器与技术 提交时间: 2024-06-06 合作期刊: 《天文技术与仪器(英文)》
摘要:The Hot Universe Baryon Surveyor (HUBS) mission will carry a nested X-ray telescope capable of observing an energy range from 0.5 keV to 2 keV to study hot baryon evolution. In this paper, we report the latest progress in the design and construction of nested X-ray telescopes which were designed to use a three-stage conicapproximation type assembly to simplify the manufacturing process. The mirror substrate is made using the thermal glass slumping method, with mirrors characterized by a root-mean-square roughness of 0.3 nm, with expected high reflectivity and good thermal stability. We also discuss methods of telescope construction and conduct a deformation analysis of the manufactured mirror. The in situ measurement system program is developed to guide the telescope assembly process.
分类: 机械工程 >> 机床技术 提交时间: 2024-05-14
摘要: In-process detection of cutting forces, temperature, roughness, wear etc. during machining of titanium alloys are very important. The Finite element (FE) analysis plays an important role in monitoring and detection of machining responses. It offers a high accuracy in modeling of dry cutting processes and its performance in modeling of cryogenic machining process is a matter of interest. In this context, current investigation focuses on the dry turning and LN2/CO2cooling assisted turning process of commonly used Ti6Al4V alloy. It is very useful material in the biomedical sector, and the simulation of cutting forces and cutting temperature via finite element method (FEM) has been performed. In addition, the simulation results are validated with experimental work. The results show that the deviations between FE modeling and experimental results for the cutting temperature are the average of 5.54%, 5.18% and 8.42% for the dry, LN2and CO2cooling conditions, respectively. On the other hand, the deviations from FE modeling and cutting force test results were 3.74%, 3.358%, and 3.03% under dry, LN2and CO2cooling conditions, respectively.
分类: 机械工程 >> 机械制造工艺与设备 提交时间: 2024-05-10
摘要: In this work, the sustainable machining approach is promoted by implementing the dry and minimum quantity lubrication (MQL) cooling conditions in the turning of duplex stainless steel. Initially, the turning experiments were performed under dry as well as MQL conditions and then, the influence of different positions of MQL nozzles on tribological and machining performance of 2205 duplex steel was investigated. The cutting parameters were kept fixed and the performance is evaluated in terms of surface roughness, micro-hardness, energy consumption, tool wear, machined surface microstructure and chips morphology. The results demonstrated that the highest average surface roughness values were obtained under dry conditions, with a value of 2.20 μm while MQL (flank + rake directions) produces the lowest surface roughness value of 1.55 μm with an improvement of 30%. Moreover, dual-jet MQL gives the lowest energy consumption (229 kJ) and tool wear (0.15 mm) with 23.67% and 52.38% enhancement, respectively.
分类: 核科学技术 >> 核科学与技术 提交时间: 2024-03-12
摘要: This paper presents a new technique for measuring the bunch length of a high-energy electron beam at a bunch-by-bunch rate in storage rings. This technique uses the time–frequency-domain joint analysis of the bunch signal to obtain bunch-by-bunch and turn-by-turn longitudinal parameters, such as bunch length and synchronous phase. The bunch signal is obtained using a button electrode with a bandwidth of several gigahertz. The data acquisition device was a high-speed digital oscilloscope with a sampling rate of more than 10 GS/s, and the single-shot sampling data buffer covered thousands of turns. The bunch length and synchronous phase information were extracted via offline calculations using Python scripts. The calibration coefficient of the system was determined using a commercial streak camera. Moreover, this technique was tested on two different storage rings and successfully captured various longitudinal transient processes during the harmonic cavity debugging process at the Shanghai Synchrotron Radiation Facility (SSRF), and longitudinal instabilities were observed during the single bunch accumulation process at Hefei Light Source (HLS). For Gaussian-distribution bunches, the uncertainty of the bunch phase obtained using this technique was better than 0.2 ps, and the bunch length uncertainty was better than 1 ps. The dynamic range exceeded 10 ms. This technology is a powerful and versatile beam diagnostic tool that can be conveniently deployed in high-energy electron storage rings.