The integration of thermal/fast neutron spectroscopy with gamma-ray detection in a single compact system remains a major challenge in radiation monitoring. Here, we present a novel dual-mode detector design based on isotopically enriched Cs _2 LiYCl _6 :Ce (CLYC) crystals coupled to high-gain silicon photomultipliers (SiPMs). By utilizing the distinct scintillation decay characteristics of CLYC for neutrons and gamma rays, we achieved excellent particle identification performance through an optimized charge-comparison pulse shape discrimination (PSD) algorithm. The ^6 Li-enriched CLYC-6 enables efficient thermal neutron detection via the ^6 Li(n, α ) ^3 H reaction, while the ^7 Li-enriched CLYC-7 exploits the ^35 Cl(n, p) ^35 S and ^35 Cl(n, α ) ^32 P reactions for fast neutron spectroscopy. Our CLYC-6 (95 ^6 Li) thermal neutron-gamma detector exhibits a gamma energy resolution of 6.52 ∼ 3.84 for thermal neutrons. The CLYC-7 (over 99 ^7 Li) fast neutron-gamma detector exhibits a gamma energy resolution of 6.73 ∼ 2.35 for fast neutrons; moreover, there is a good linear relationship between the fast neutron energy and the corresponding peak position in the energy spectrum. The quenching factors for protons and α particles are calculated to be 0.90 and 0.53, respectively, for the reactions ^35 Cl(n, p) ^35 S and ^35 Cl(n, α ) ^32 P. Our measurements demonstrate that the SiPM-based readout not only supports significant miniaturization but also preserves the excellent intrinsic spectral performance of CLYC. This work lays a solid experimental foundation for next-generation portable, magnetic-field-insensitive multi-mode radiation spectrometers.

The search for light dark matter and cosmic primordial neutrinos necessitates detectors with sub-millielectronvolt (sub-meV) energy thresholds. While superconducting quantum sensors have approached this sensitivity, they often face significant challenges regarding readout complexity and scalability. To address these limitations, we propose a hybrid Superconductor-Insulator-P-N (S-I-P-N) detector architecture. This concept combines the high sensitivity of superconducting Cooper pair breaking with the massive intrinsic gain of semiconductor electron avalanches. A critical prerequisite for this scheme is operation at millikelvin (mK) temperatures, raising the critical fundamental question of whether silicon PN junctions can sustain avalanche multiplication in a regime where carrier freeze-out is severe. Here, we experimentally validate the critical semiconductor amplification stage of the proposed detector. We demonstrate that Silicon Photomultipliers (SiPMs) retain robust Geiger-mode avalanche capabilities at 10 mK. We report a single-photoelectron gain of order 10^6 and a dark count rate as low as 5 mHz/mm^2, 7 orders of magnitude lower than at room temperature. These results confirm the viability of high-gain semiconductor readout in the deep cryogenic regime, clearing the primary obstacle regarding the semiconductor component for the realization of scalable, sub-meV threshold S-I-P-N detectors.

Irradiation damage is one of the main drawbacks restricting the application of Silicon Photomultiplier (SiPM), especially in high irradiance environments such as space, colliders, and nuclear power plants. In-situ current annealing is a method of using the self-current heating of SiPM, and because it does not require disassembly of the SiPM and additional heating devices, it exhibits potential for dealing with radiation damage. We investigate the in-situ annealing performance of three types of SiPM for irradiation damage. The annealing current and time are optimized and the SiPM performance before and after annealing is compared. It was found that after annealing the dark currents of the three types of SiPMs decreased significantly by 1–2 orders of magnitude. Finally, the variation of SiPM performance with temperature is investigated. The energy resolution does not recover as well as the dark current.

Purpose Radon is a noble gas, which endangers our health. The liquid scintillator is one of the detector materials used to measure radon in the environment. But there are challenges in measuring radon using a liquid scintillator, such as independent manual operation and long measurement periods. Methods and Results We propose a liquid scintillator detector for the rapid measurement of radon, which is composed of a breathable liquid scintillator probe and photomultiplier tube. Cascade decay recognition and pulse shape discrimination (PSD) were used to select radon events. (241)Am4(alpha) and Sr-90(beta) source calibration was used to optimize the PSD figure of merit of the liquid scintillator, and a Th-232 (Rn-220) diffusion source was used to verify the function of this novel detector for measuring radon. Conclusion The detector had an integrated design for sampling and measurement, which simplified the measurement steps. Thus, this novel liquid scintillator detector demonstrated promise for use in radon-detection systems.

基于反应堆流动冷却剂水中l6O(n,p)l6N核反应产生的l6N特征γ 谱的在线探测可实现水冷堆的功率监测,在高通量工程试验堆(HFETR)一回路上设计了一套用于一次水l6N特征γ谱在线探测的辐射监测系统,并基于l6N特征γ谱能量区间内的计数率,首次开展了整个炉段的反应堆功率在线监测实验.实验表明,在合适的屏蔽铅室设计与几何布置条件下,基于l6N特征γ谱功率监测系统的l6Nγ计数率与功率线性关系较好,总计数率的死时间与l6Nγ计数率本底较低等优点,可实现反应堆功率量程范围的核功率的准确测量,为水冷堆l6N辐射监测提供数据参考.

To increase redundancy and diversity of the reactor power measurement, a system for the measurement of reactor power can be established based on neutron activation analysis using O-16(n,p)N-16 reaction. In this work, gamma spectrums from the coolant of HFETR core are continuously detected by N-16 monitor with NaI(Tl) detector and the count rates in the spectrum range of 4.5 MeV-7.5 MeV are obtained. Meanwhile, the overlapping peaks in the given spectrum range are decomposed with LevenbergMarquardt method during the operation of HFETR. The results confirm that the count rates of full energy peak, single-escape peak and double-escape peak of 6.13 MeV gamma spectrums is proportionate to the increased reactor power measured by other monitors such as compensated ionization chamber and thermal power. It is possible to achieve the absolute nuclear power measurement by adopting the count rate of N-16 6.13 MeV peak, detection efficiency of detector and N-16 source term. (C) 2021 Published by Elsevier Ltd.

BackgroundThe Shashlik electromagnetic calorimeter (ECAL) is used in the Nuclotron-based Ion Collider Facility's MultiPurpose detector (NICA-MPD) of the Russian heavy ion superconducting synchrotron. It is designed as a cylindrical barrel divided into 32 sectors with a total of 43 008 towers. Each tower is composed of 220 layers of lead and 221 layers of scintillator alternately.PurposeThis study aims to simulate multiple parameters of Shashlik ECAL for NICA-MPD that affect the performance of ECAL.MethodsFirst of all, the module of ECAL tower was built based on the principle of Shashlik ECAL. Then, the GEENT4 software was employed to simulate the performance of every single tower of ECAL according to its structure composition. Considering the influence of the design parameters of the scintillator and absorber on energy deposition, energy resolution, and energy leakage after electrons were incident on the tower and the subsequent scintillator luminescence process, the influence of the reflective layer on the number of photons was in the wavelength shifted fiber and detector. Finally, factors that affected energy deposition, energy leakage, energy resolution, and photon number in the wavelength shift (WLS) and sensor, and the influence of the thickness, number of layers, and size of the scintillator and absorber in the module on energy deposition, energy leakage, and energy resolution were simulated and analyzed.ResultsThe simulation results show that the best side length of cross-section of each tower is 4 cm. When the total thickness of absorber and scintillator is 1.8 mm and the thickness of lead absorber is 0.3 mm, the energy resolution meets the experimental requirements of 5%@3 GeV. When the radiation length reaches 13X0, maximum energy deposition and obtains better energy resolution can be achieved. Adding a reflective layer to the tower side can increase the number of photons in the fiber by 10%~19% whereas adding a reflective coating to the fiber end can effectively increase the number of photons reaching the detector by 50%.ConclusionsThe photon numbers in the wavelength shift fiber and the detector are affected by the reflection layer on both the tower side and the end face of the fiber. The importance and necessity of adding reflector are verified by this study.

对福清核电1、2号机组烟囱取样代表性进行了分析与计算,结果表明:烟囱取样位置满足标准要求,但取样系统布置存在一定的问题,导致气溶胶传输比达不到标准的要求.根据气溶胶在管道中的传输特性,结合现场实际烟囱和流出物监测仪的布置位置,本文提出了烟囱内和厂房内取样管道敷设的改进方案.通过计算,改进后的取样系统对10 μm空气动力学直径的气溶胶传输比大于50％,满足气载流出物取样代表性的要求.

为确保核电站安全运行,需要对放射物泄漏情况实施监测,防止出现安全事故,影响人员安全.辐射监测仪可组成KRT系统,并形成信息传输通道.本文对辐射监测仪的组成结构进行了简要介绍,明确了监测系统结构和工作原理,阐述了常见的仪表故障类型,并针对不同故障,提出了程序化的检修模式.

提出了一种利用符合技术降低本底来提高放射性监测仪器测量下限的方法.当放射源项寿命短且具有级联关系时,存在标准体源难以制备和本底计数过高的问题,针对这两个问题,探讨了一种基于点源模拟法的体源全能峰测量实验方法,该方法使用22Na来代替标准13N源项,测量了直径为290 mm、300 mm、350 mm、400 mm的体源全能峰符合探测效率,并用Geant4软件进行了符合效率模拟计算.结果 对比发现,在9.2％的误差范围内,实验测量与模拟计算的结果保持一致,表明用该方法测量符合效率具有可行性、可信性,可应用于核电单位测量符合效率.

针对MC法模拟计算16Nγ能谱功率监测仪探测效率误差较大问题,采用了直接计算、分段衔接与剂量估算三种方法,分析了某压水堆基于γ能谱的16N功率监测仪设计,三种方法根据该设计模拟得出的探头计数率结果接近,验证了三种计算方法的一致性,提供了可靠的16N监测仪探测效率模拟结果.

The N-13 coincidence method is an effective approach for monitoring the primary loop leakage in pressurized water reactors. The high coincidence efficiency and low background are crucial to achieving a lower limit of measurement for such a monitoring system. In this paper, we proposed four types of geometric designs of the sampling composing NaI(TI) detector. For varying container volumes (V), the detection efficiency (ε) of these containers was investigated through the Geant4 simulation and experimental measurement. The value of ε•V, which is a key combined parameter, was obtained accordingly. Finally, we obtained the optimal size of the suitable sampling and detection container for the coincidence method.

采用高低温试验方法探究了温度变化对NaI(Tl)闪烁探测器性能及能谱测量的影响,观察能谱并以常温25°C为基准,计算137Cs的0.662 MeV、60Co源1.173 MeV,1.332 MeV特征峰位道址、γ射线全能峰计数率、能量分辨率在25°C下相对变化值.结果为:137Cs的0.662 MeV、60Co源1.173 MeV,1.332 MeV特征峰位道址在0°C～20°C范围内基本保持一致,在20°C～45°C范围内随温度升高逐渐降低;0.662 MeV和1.173 MeV全能峰计数率随温度变化分别在±5.19％和±4.48％范围内保持一致;3个对应能量分辨率分别在±4.3％范围内随温度变化保持一致.可看出利用γ源作为稳峰源是可行的.

将三维水箱中央控制单元在数据采集时分别放置于离加速器小机头1 m、4m处,在保证其余条件和采集流程不变的情况下先后采集两套数据,比较两套数据的差异.使用Oncentro计划系统分别基于以上两套数据进行建模,比较开野和临床病例剂量计算结果的差异.实验结果表明:百分深度剂量和射野离轴比野外剂量偏高,小野输出因子偏大,大野输出因子偏小.用受加速器机头散射影响较大的数据建模后,方野和病人剂量计算结果均较正常数据明显偏高.

安全壳内13N气体浓度的精确测量是核电厂一回路压力边界泄漏监测的关键问题,利用计算流体力学软件FLUENT,初步研究了一回路中子活化产物13N泄漏后在安全壳内的输运过程,获得安全壳内不同区域的浓度大小.计算结果表明:在1aN气体泄漏700 s后,各代表区域浓度以700～ 750 s时间段平均浓度值为基准在1.70％范围内保持稳定,不同区域13N气体具体浓度有助于13N辐射监测仪器获取准确度更高的一回路泄漏量.

为提高核电站安全壳内一回路管道破损泄漏出的中子活化产物18 F浓度的测量精度,利用数值模拟方法,初步研究了一回路中子活化产物18 F泄漏后在安全壳内的传输机理,获得了18 F随时间变化在安全壳内浓度分布云图、速度云图,在取样点体积浓度随时间变化情况.数值模拟结果表明:在反应堆本体发生泄漏900 s后,安全壳内18 F扩散趋于稳定,达到动态平衡状态;18 F在安全壳内浓度分布呈现分层特点,上层空间浓度高于下部空间;不同监测区域18 F体积浓度存在差别,据此有助于18 F辐射监测仪器获取准确度更高的一回路泄漏率.

[Background] With the development of radiation technology, it needs to improve the accuracy of dose simulation. [Purpose] Build up a simplified benchmarking procedure to determine the incident electron beam parameters independently using a Monte Carlo linear accelerator model. [Methods] A 10 cm×10 cm field is simulated to acquire the parameters influence on the dose distributions for Varian IX 6 MV megavoltage electron beams. [Results] The calculated depth doses had no significant changes when the electron mean energy and radial intensity varied in 5.5～6.4 MeV and 0.1～0.4 cm respectively. And the dose profile simulated with an electron radial intensity in 0～0.19 cm had a good agreement with the measured dose profile in the main field while obvious discrepancies in the penumbra region. The mean angular spread was found to be 0.3° to get good matching between calculations and measurements at all considered depths. [Conclusion] Accurate dose distributions are achieved by using the incident electron beam parameters benchmarked with the proposed procedure. As the percentage depth doses and dose profiles are insensitive to the electron energy and radial intensity correspondingly, they are feasible to benchmark individually.

结合南华大学的地方特色、办学理念和人才培养定位,积极探索适合地方院校的核工程与核技术专业"卓越计划"人才培养模式,从人才培养模式理论探索、方案优化、实践探索三个层次进行探索与实践.

Objective To determine the optimal electron beam energy at different field size through a Monte Carlo-based simulation of the therapy head of Varian X 6 MV linear accelerator so as to study the influence of radial intensity on depth dose.Methods Firstly,keeping the radial intensity unchanged for the field of interest while changing electron beam energy,compassion was carried out of calculated percentage depth doses between measured values.Thus,the optimal energy was identified for this field size.Then,the obtained energy was set the optimal value to study the radial intensity influence on the depth doses.Results The optimal electron energy for 4 cm ×4 cm,10 cm × 10 cm,20 cm × 20 cm and 30 cm × 30 cm field sizes was 5.9,6.0,6.3 and 6.4 MeV respectively.Changes in radial intensities resulted in negligible changes in percentage depth doses for4 cm ×4-cm and 10 cm × 10 cm fields,but led to observable discrepancy for 20 cm × 20 cm and 30 cm × 30 cm fields.Conclusions The optimal electron energies for different field sizes are slightly different.Change in radial intensity distribution has significant influence on the depth dose for large field.To improve simulation accuracy,the field size needs to be taken into consideration in determining the electron beam energy and radial intensity distribution.

Background:The silicon photomultiplier (SiPM) is a new type of photo detector consisting of avalanche photodiode arrays operated in Geiger mode.Its photocoupling performance with scintillation crystal is helpful for gamma spectrometry.Purpose:This study aims to provide a reliable tool for the design of scintillation detector photocoupling with SiPM to achieve effective gamma spectrometry with the GEANT4 code.Methods:GEANT4 toolkit is used to simulate NaI(TI) and LaBr3:10％Ce3+ scintillation crystal detect 662-keV γ-ray photocoupling with SiPM by building a complete Monte Carlo model of a scintillator includes ionizing particle and optical photon transport.Energy resolution of 662-keV gamma spectrum is modified with the contribution of dark current noise amplified by the electronic system and statistical fluctuation of optical photon absorbed by avalanche photodiode of SiPM which was previously illuminated with monochromatic LED light.Results:Simulation results show that energy resolution of 662-keV gamma spectrum is in accordance with the result of experimental measurement.A group of parameters (Pr,s) which corresponded to scintillation crystal intrinsic energy resolution is obtained simultaneously.Conclusion:The GEANT4 simulation of NaI(TI) and LaBr3:10％Ce3+ scintillation crystals photocoupling with SiPM for 662-keV γ-ray spectrometry results consistently with experimental energy spectrum,and confirms the reliability and rationality of material properties and parameters which set in GEANT4 toolkit.