分类： 物理学 >> 核物理学 提交时间： 2016-09-09
摘要： The search for Gamma Ray Burst (GRB) emission in the energy range 1-100 GeV in coincidence with the satellite detection has been carried out using the Astrophysical Radiation with Ground-based Observatory at YangBaJing (ARGO-YBJ) experiment. The high altitude location (4300 m a.s.l.), the large active surface (∼ 6700 m2 of Resistive Plate Chambers), the wide field of view (∼2 sr, limited only by the atmospheric absorption) and the high duty cycle (> 86 %) make the ARGO-YBJ experiment particularly suitable to detect short and unexpected events like GRBs. With the scaler mode technique, i.e., counting all the particles hitting the detector with no measurement of the primary energy and arrival direction, the minimum threshold of ∼ 1 GeV can be reached, overlapping the direct measurements carried out by satellites. During the experiment lifetime, from December 17, 2004 to February 7, 2013, a total of 206 GRBs occurring within the ARGO-YBJ field of view (zenith angle θ ≤ 45∘) have been analyzed. This is the largest sample of GRBs investigated with a ground-based detector. Two lightcurve models have been assumed and since in both cases no significant excess has been found, the corresponding fluence upper limits in the 1-100 GeV energy region have been derived, with values as low as 10−5 erg cm−2. The analysis of a subset of 24 GRBs with known redshift has been used to constrain the fluence extrapolation to the GeV region together with possible cutoffs under different assumptions on the spectrum.
分类： 物理学 >> 核物理学 提交时间： 2025-01-05
摘要： The qualitative identification and quantitative analysis of radioactive nuclides in unknown environments are essential for remote monitoring and prompt early warning of radioactive contamination. In recent years, deep learning techniques have made significant strides in automated qualitative identification. However, the quantitative analysis of radioactive nuclides still depends on traditional methods to determine peak positions and boundaries. These methods often require extensive manual expertise and parameter tuning, which makes it challenging to meet the demands of unmanned remote monitoring. This paper presents a novel framework for automatic full-energy peak segmentation, named YOLOSpecNN. We introduced a multi-Root Mean Square Error (RMSE) joint optimization function and developed a unified regression model capable of simultaneously predicting the central position, boundaries, and confidence of full-energy peaks. To address the challenge of low recall rates due to narrow, weak, and overlapping peaks, we proposed a new multi-scale context feature extraction module (MSNN module). This module effectively enhanced local detail features, significantly improving recall rates. The effectiveness of the proposed method was validated using six artificial radioactive nuclides (241Am,57Co,131I,134Cs,137Cs,and 60Co), along with 40K, to construct a mixed energy spectrum dataset for quantitative evaluation. Experimental results show that the proposed method significantly outperforms traditional approaches, achieving a precision of 0.998, recall of 0.95, and the best F1 score of 0.974@0.427, and the average precision of 0.946. Compared to traditional morphological methods, the proposed method improves precision, recall, and the best F1 score by 0.512, 0.199, and 0.391, respectively. Ablation experiments further reveal that the MSNN module notably enhances recall, with an improvement of 0.067. Moreover, the proposed method performs excellently even in challenging environments with low gross counts and low Signal-to-Noise Ratio (SNR), achieving state-of-the-art (SOTA) results. Additionally, the model achieves an average real-time inference performance of 16.1941 ms on a 15 W low-power device. Overall, the proposed method demonstrates exceptional performance in the automatic search and segmentation of full-energy peaks, offering robust support for the implementation of unmanned remote radiation monitoring systems.
分类： 物理学 >> 核物理学 提交时间： 2016-09-14
摘要： In quantum gravity, a foamy structure of space-time leads to Lorentz invariance violation (LIV). As the most energetic astrophysical processes in the Universe, gamma-ray bursts (GRBs) provide an effective way to probe quantum gravity effects. We use continuous spectra of 20 short GRBs detected by the Swift satellite to give a conservative lower limit of quantum gravity energy scale MQG. Due to the LIV effect, photons with different energy have different velocities. This will lead to the delayed arrival of high energy photons relative to the low energy ones. Based on the fact that the LIV-induced time delay can't be longer than the duration of a GRB, we present the most conservative estimation of the quantum gravity energy scales from 20 short GRBs. The most strict constraint,MQG>5.05* 1014 GeV, is from GRB 140622A.
分类： 核科学技术 >> 核材料与工艺技术 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： The present work investigated the radiolysis of HA (Humic acids) in aqueous solutions and under gamma radiation. Absorbances at the range of 200‒800 nm and chemical oxygen demand (COD) were used to characterize the degree of degradation of HA. The results indicated that absorbances and the concentrations of COD were decreased with increasing of irradiation dose while with increasing of irradiation dose the pH of the solutions was decreased at first and then increase. In addition, the effects of initial pH and primary solution concentrations on HA degradation were also investigated. It is shown that the higher primary solution concentrations, the lower degradation efficiency under the same irradiation dose. And the degradation efficiency of HA under neutral conditions is better than in acidic or alkaline conditions.
分类： 物理学 >> 核物理学 提交时间： 2025-03-27
摘要： Detection of threatening radioactive sources is a crucial task for homeland security. One of the major challenges in radiation detection is to distinguish between the background radiation and the anomalous source radiation from the measured radiation spectrum at low source to background ratio. In this paper, an anomaly detection technique is proposed to detect anomalous Gamma-ray radiation spectra using machine learning. The method is based on dividing the radiation spectrum into two sub-spectra, where the background part of the second sub-spectrum is predicted from the first sub-spectrum through a neural network model. Hence, an anomaly spectrum is detected according to the difference between the predicted background radiation data and the measured values of the second sub-spectrum. The ant colony optimization is utilized to select, from the radiation spectrum, the values assigned to the first and second sub-spectra, where optimum prediction accuracy can be provided. To present the effectiveness of the proposed work, a performance comparison is conducted with both benchmark and a recent neural network-based method. The performance is evaluated using real data that represent both background and radioactive source radiation, which are measured through a network of detectors. Experimental results show that the proposed method outperforms the other methods in terms of the detection capability even at low source to background radiation ratios.
分类： 物理学 >> 核物理学 提交时间： 2024-03-19
摘要： In recent years, the gap between the supply and demand of medical radioisotopes has increased, necessitating new methods for producing medical radioisotopes. Photonuclear reactions based on gamma sources have unique advantages in terms of producing high specific activity and innovative medical radioisotopes. However, the lack of experimental data on reaction cross sections for photonuclear reactions of medical radioisotopes of interest has severely limited the development and production of photonuclear transmutation medical radioisotopes. In this study, the entire process of the generation, decay, and measurement of medical radioisotopes was simulated using online gamma activation and offline gamma measurements combined with a shielding gammaray spectrometer. Based on a quasi-monochromatic gamma beam from the Shanghai Laser Electron Gamma Source (SLEGS), the feasibility of the measurement of production cross section for surveyed medical isotopes was simulated, and specific solutions for measuring medical radioisotopes with low production cross sections were provided. The feasibility of this method for high precision measurements of the reaction cross section of medical radioisotopes was demonstrated.
分类： 核科学技术 >> 核材料与工艺技术 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： The formation of bromate, a classified potential carcinogen, is of great concern when disinfection processes are used for treating high-bromide drinking waters. Bromide-containing aqueous solutions with various additives were irradiated by 60Co source. With a 2.0 kGy irradiation of N2O-saturated solutions at initial bromide concentrations of 180.2 gl-1, 416.9 gl-1, 663.1 gl-1 and 823.9 gl-1. 79.5%, 84.0%, 87.3% and 88.3% of bromide ions were transformed to bromate, respectively. Addomg CO32-/HCO3- or NO3- ions into N2O-saturated bromide solutions, the amount of bromate ions formed decreased with increasing concentrations of the additives. On the other hand, the bromate concentration was all below the detection limit of 1 gl-1 whenever N2O was not added to quench eaq- and H. The results indicated that -rays irradiation could be used as a disinfection process, instead of ozonation, to comply with upcoming more stringent regulations, especially in waters containing high concentrations of bromide.
分类： 物理学 >> 核物理学 提交时间： 2025-07-07
梁, Dr. 杰
Wang, Mr. Ke-liang
Guo, Dr. Ji-ping
Zhang, Mrs. Fan
Wu, Ms. Ya-qin
Jun, Prof. Yang
Zhun, Prof. Ying-chun
摘要： This paper reports an experimental investigation into the backscatter effects on gamma radiation monitors. The study addresses deviations in measurement readings observed in wall-mounted monitors compared to free-air devices due to backscatter phenomena. Reinforced concrete test blocks were employed to simulate operational environments, with measurements conducted using three detector types: a radiation protection level dosimeter with ionization chamber, an air-kerma radiation monitor with counter tube, and a radiation detector with NaI(Tl) scintillator. Analysis of backscatter factors at varying distances and orientations revealed that: (1) backscatter factors decreased with increasing source-to-surface distance, and (2) central irradiation generally yielded higher backscatter factors than non-central irradiation. The experimental data provide essential reference for formulating or revising pertinent technical standards.
分类： 物理学 >> 核物理学 提交时间： 2024-12-13
Wang, Dr. Jin-Long
Yang, Mr. Li-Wang
Wu, Prof. Xiao-Guang
Li, Mr. Jin-Ze
Hong, Mr. Rui
Zhou, Mr. Jia-Nan
Guan, Mr. Shao-Xiong
Shi, Miss Jing
He, Mr. Zi-Yang
Yun, Prof. Zheng
Li, Dr. Cong-Bo
Li, Mr. Tian-Xiao
Zhao, Mr. Zi-Hao
Zheng, Miss Min
Li, Miss Yun-Qiu
摘要： A new pixelated prompt gamma imaging detector (PPGID) was developed for prompt gamma spectrum and gamma source position measurement. The PPGID prototype is composed of 30 independent pixelated scintillator detectors that can simultaneously obtain the gamma spectrum. The prototype has two LaBr3 scintillator modules for gamma ray spectrum measurement with good performance in terms of energy resolution and one BGO module with high efficiency in high-energy detection. Therefore, in this study, a compound advanced imaging device based on energy spectrum detection was designed, assembled, and tested with radioactive sources; This device is called a pixelated prompt gamma imaging detector system (PPGID). The PPGID can correctly measure the source position as predicted by the FOV mathematical model. Both LaBr3 and BGO can reproduce the gamma spectrum of the radioactive source. The tested energy response of LaBr3 is 0.03~2.6 MeV, and that of BGO is 1~2.6 MeV with 22Na and 232Th. Dedicated data acquisition software was developed for energy calibration and gamma count histogram distribution. The gamma count histogram can be transformed into a thermal map which is the basis of the image.
分类： 数学 >> 数学（综合） 提交时间： 2022-08-13
摘要： This paper shows thatthe endograph metric and the $\Gamma$-convergenceare compatible on a large classof fuzzy set in $\mathbb{R}^m$.
分类： 物理学 >> 核物理学 提交时间： 2016-09-14
Xiaoyuan Huang
Anna S. Lamperstorfer
Yue-Lin Sming Tsai
Ming Xu
Qiang Yuan Jin Chang
Yong-Wei Dong
Bing-Liang Hu
Jun-Guang L╱
Le Wang
Bo-Bing Wu
Shuang-Nan Zhang
摘要： HERD is the High Energy cosmic-Radiation Detection instrument proposed to operate onboard China's space station in the 2020s. It is designed to detect energetic cosmic ray nuclei, leptons and photons with a high energy resolution (∼1% for electrons and photons and 20% for nuclei) and a large geometry factor (>3m2sr for electrons and diffuse photons and >2m2sr for nuclei). In this work we discuss the capability of HERD to detect monochromatic γ-ray lines, based on simulations of the detector performance. It is shown that HERD will be one of the most sensitive instruments for monochromatic γ-ray searches at energies between ∼10 to a few hundred GeV. Above hundreds of GeV, Cherenkov telescopes will be more sensitive due to their large effective area. As a specific example, we show that a good portion of the parameter space of a supersymmetric dark matter model can be probed with HERD.
分类： 物理学 >> 核物理学 提交时间： 2016-09-09
摘要： The ARGO-YBJ air shower detector monitored the Crab Nebula gamma ray emission from 2007 November to 2013 February. The integrated signal, consisting of ∼3.3 × 105 events,reached the statistical significance of 21.1 standard deviations. The obtained energy spectrum in the energy range 0.3-20 TeV can be described by a power law function dN/dE = I0 (E / 2 TeV)−α, with a flux normalization I0 = (5.2 ± 0.2) × 10−12 photons cm−2 s−1 TeV−1and α = 2.63 ± 0.05, corresponding to an integrated flux above 1 TeV of 1.97 × 10−11 photons cm−2 s−1. The systematic error is estimated to be less than 30% for the flux normalization and 0.06 for the spectral index. Assuming a power law spectrum with an exponential cutoff dN/dE = I0 (E / 2 TeV)−α exp (-E / Ecut), the lower limit of the cutoff energy Ecut is 12 TeV, at 90% confidence level. Our extended dataset allows the study of the TeV emission over long timescales. Over five years, the light curve of the Crab Nebula in 200-day bins is compatible with a steady emission with a probability of 7.3 × 10−2. A correlated analysis with Fermi-LAT data over ∼4.5 years using the light curves of the two experiments gives a Pearson correlation coefficient r = 0.56 ± 0.22. Concerning flux variations on timescales of days, a "blind" search for flares with a duration of 1-15 days gives no excess with a significance higher than four standard deviations. The average rate measured by ARGO-YBJ during the three most powerful flares detected by Fermi-LAT is 205 ± 91 photons day−1, consistent with the average value of 137 ± 10 day−1.
分类： 核科学技术 >> 核探测技术与核电子学 提交时间： 2025-04-06
摘要： In-situ exploration of deep-sea seabed resources is a valuable research direction. Neutron activation-based in-situ exploration methods for seabed polymetallic nodules or crust resources are theoretically feasible because of the high content and high neutron capture cross-section of manganese in these nodules or crusts. However, to date, only a few relevant studies have been conducted. In this study, a prototype Deep-sea In-situ Neutron Activation Spectrometer (DINAS) was designed for resource exploration. Through an analysis of the principles of the spectrometer combined with Monte Carlo simulations of the physical principles and finite element simulations of deep-sea pressure, the structure and fundamental components of the spectrometer were determined. The inner core of the spectrometer comprised three components: a compact neutron generator for neutron production, gamma-ray detectors, and an electronics system. The gamma-ray detector array of the spectrometer consisted of LaBr3 and BGO scintillation crystals coupled with silicon photomultiplier (SiPM) arrays. The electronics system was divided into two modules to implement the SiPM readout and digital signal analysis along the modular design lines. The experimental activation of neutron beamlines at the China Spallation Neutron Source demonstrated the capability of the spectrometer detectors to detect activated gamma rays and showed that the spectrometer achieved an energy resolution of 2.8 % at 847 keV for the LaBr3 detector and 6.7 % at 2.113 MeV for the BGO detector. The laboratory model experiment tested the functionality of the spectrometer prototype, whereas the Geant4 simulation verified the reliability of the Monte Carlo method. The method and prototype proposed in this study proved feasible for the in-situ detection of polymetallic nodules or crusts in deep-sea environments
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-09
摘要： We propose a model in which an energy-dependent time delay of a photon originates from space-time non-commutativity, the time delay is due to a non-commutative coupling between dilaton and photon. We predict that in our model, high energy photons with different momentum can either be delayed or superluminal, this may be related to a possible time delay reported by the Fermi LAT and Fermi GBM Collaborations
分类： 物理学 >> 核物理学 提交时间： 2025-03-20
Feng, Mr. Yuhan
Dong, Ms. Yixin
Liang, Mr. Yongfei
Bai, Dr. Lixin
Xia, Dr. Bangyang
Yang, Prof. Chaowen 杨朝文
摘要： Lead-cooled fast reactors are considered the next generation of nuclear reactors. One of the main challenges in developing lead-based fast reactors is the corrosion of structural materials by the liquid lead-bismuth coolant, as well as the formation of oxide particulates.It is an urgent need to develep a high-resolution non-destructive testing method for the detection of oxides and corrosion in pipeline of liquid lead-bismuth coolant. This paper investigates the feasibility of passive gamma emission tomography (PGET), a technique that utilizes gamma rays emitted by the lead-bismuth coolant, which is activated by neutrons in the reactor core, to inspect the lead-bismuth coolant pipelines corrosion. A simulation model of the PGET system was developed, including the test pipeline, collimator, and detector array. Projection data were obtained using the Geant4 Monte Carlo method. Image reconstruction was performed using the Algebraic Reconstruction Technique (ART), Maximum-Likelihood Expectation-Maximization (MLEM), and Ordered-Subsets Expectation-Maximization (OSEM), and an edge extraction method is proposed. With a collimator length of 90 mm and hole diameter of 1.1 mm, the reconstructed images achieved a resolution of 1.5 mm.
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-07-31
摘要： Short-lived medical isotopes and their generators are typically produced in nuclear reactors and cyclotrons that require extensive facilities. However, considering the environmental concerns and economic costs of these traditional approaches, modern laser technology, which provides extremely strong electric fields within tabletopsized areas, can serve as a potential supplementary method. Focusing specifically on the (γ, p) generation of the vital medical isotopes 47Sc and 67Cu, we used both experimental results and PIC-GEANT4 simulations to demonstrate that laser-induced photonuclear reaction is a promising method for isotope production. We developed a model capable of calculating isotope yields under various laser conditions and acceleration mechanisms. The findings revealed that a 200 TW laser can sufficiently produce diagnostic amounts of 47Sc and 67Cu, while simultaneously providing high specific activity, which is significant in medical applications for improving treatment efficacy, enhancing image resolution, and reducing side effects.
分类： 核科学技术 >> 粒子加速器 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： The absolute dose difference of the iso-center position at different times was used to evaluate the stability of medical linear accelerator (LINAC). In order to eliminate the drawback of point dose without statistical significance and to investigate the output stability of segment with small weight related to intensity-modulated radiotherapy (IMRT), a modified method of evaluating the stability of LINAC was proposed based on planar dose combined with gamma method. With a commercial available two-dimensional ionization chamber, a set of planar doses with dose gradient from 2 cGy to 100 cGy were obtained. Then the gamma method was adopted to analyze the dose difference between the reference data and the evaluated data at each dose level. The results showed that the improved method based on planar dose for analyzing the output stability of the medical LINAC was feasible and efficient, and suggested that the reverse optimization should be aborted in clinical when the segment weight related to IMRT was under 10 MU.
分类： 物理学 >> 凝聚态:结构、力学和热性能 提交时间： 2017-03-23
Jing Zhang
Abu Zayed Mohammad Saliqur Rahman
Yuxiao Li
Jing Yang
Yaru Wu
Daqing Yuan
Xingzhong Cao
Runsheng Yu
Baoyi Wang
摘要： A comparative study on the morphology, structure and luminescence modifications of LDPE–Na2SO4:Sm3+ composite induced by gamma irradiation was reported for the first time. The composites were irradiated with irradiation doses of 10, 30, and 50 kGy in air at room temperature. Modifications on structural and luminescence properties of LDPE–Na2SO4:Sm3+ composites were investigated by using several analytical methods. The X-ray diffraction (XRD) patterns revealed that the cross-linking improved the crystallinity of the composites. Scanning electron microscope (SEM) images illustrated the surface modifications of composites induced by irradiation. Results of positron annihilation lifetime spectroscopy (PALS) suggested that gamma irradiation affected the free volumes concentrations in the samples. The photoluminescence (PL) spectra of non-irradiated and irradiated composites consisted of four main peaks at 563, 598, 644 and 706 nm which could be assigned to the 4G5/2 6HJ (J =5/2, 7/2, 9/2 and 11/2, respectively) transitions within the electronic configuration of Sm3+. Meanwhile, we observed an additional peak at about 686 nm in the irradiated composites, owing to the conversion of Sm3+ Sm2+. Concentrations of the Sm2+ centers linearly increased with gamma irradiation doses, which partly accounted for the degradation of PL intensity of Sm3+ peaks.
分类： 核科学技术 >> 核探测技术与核电子学 提交时间： 2025-06-12
摘要： While traditional gamma-gamma density (GGD) logging technology is widely utilized, its potential environmental risks have prompted the development of more environmentally friendly neutron-gamma density (NGD) logging technology. However, NGD measurements are influenced by both neutron and gamma radiation. In the logging environment, variations in formation composition indicate different elemental compositions, which affect neutron-gamma reaction cross-sections and gamma generation. Compared to traditional gamma sources such as Cs-137, these changes can significantly impact the generation and transport of neutron-induced inelastic gamma rays, posing challenges for accurate measurements. To address this, a novel method is proposed, the method incorporates the mass attenuation coefficient function to account for the effects of various lithologies and pore contents on gamma-ray attenuation and therefore can achieve more accurate density measurements by clarifying the transport processes of inelastic gamma rays with varying energy and spatial distributions in varied logging environments. The method avoids the complex correction of the neutron transport and is verified through Monte Carlo simulations for its applicability across various lithologies and pore contents. showing thatthe absolute density errors are less than 0.02 g/cm3 in clean formations and demonstrating good accuracy. The research not only clarifies the NGD mechanism but also provides theoretical guidance for the application of NGD logging methods. Further research will be conducted regarding extreme environmental conditions and tool calibration.
分类： 物理学 >> 核物理学 提交时间： 2025-04-23
摘要： While traditional gamma-gamma density (GGD) logging technology is widely utilized, its potential environmental risks have prompted the development of more environmentally friendly neutron-gamma density (NGD)logging technology. However, NGD measurements are influenced by both neutron and gamma radiation. In the logging environment, variations in formation composition indicate different elemental compositions, which affect neutron-gamma reaction cross-sections and gamma generation. Compared to traditional gamma sources such as Cs-137, these changes can significantly impact the generation and transport of neutron-induced inelastic gamma rays, posing challenges for accurate measurements. To address this, a novel method is proposed, the method incorporates the mass attenuation coefficient function to account for the effects of various lithologies and pore contents on gamma-ray attenuation and therefore can achieve more accurate density measurements by clarifying the transport processes of inelastic gamma rays with varying energy and spatial distributions in varied logging environments. The method avoids the complex correction of the neutron transport and is verified through Monte Carlo simulations for its applicability across various lithologies and pore contents. showing that the absolute density errors are less than 0.02 g/cm^3 in clean formations and demonstrating good accuracy. The research not only clarifies the NGD mechanism but also provides theoretical guidance for the application of NGD logging methods. Further research will be conducted regarding extreme environmental conditions and tool calibration.
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