锂玻璃探测器中子探测效率的刻度

为了精确测量keV能区的中子俘获截面,中国原子能科学研究院正在建造一台4π 全吸收型γ 探测装置---GTAF,锂玻璃探测器将会作为中子束流监视器测量中子能谱。利用5SDH-2 加速器刻度了锂玻璃探测器在两个入射中子单能点(250 和565 keV) 的探测效率,并使用EANT4 和MCNP 程序模拟计算了锂玻璃探测器的相对探测效率。通过归一化实验数据和模拟结果,得到了锂玻璃探测器在10keV~1 MeV 能区的中子探测效率曲线。对于把锂玻璃探测器测量得到的飞行时间谱转化为中子束流能谱,是一项非常重要的工作,同时为探测器效率刻度提供了新方法。In order to accurately measure the neutron capture cross section in the energy range of keVMeV, 4 πgamma-ray total absorption facility (GTAF) is being constructed at China Institute of Atomic Energy (CIAE). The lithium glass detector will be used as a neutron beam monitor for GTAF. The detection efficiency of the lithium glass detector at two incident neutron energy points (250, 565 keV) was calibrated in 5SDH-2 accelerator, and the relative detection efficiency was simulated by GEANT4 and MCNP code. By the normalization of the experimental data and simulation result, the neutron detection efficiency curve of the lithium glass detector between 10 keV and 1 MeV was obtained. This work will be important to convert the Time-of-flight spectrum that be measured by Li-glass detector to the energy spectrum of neutron beam, and provide the new method for calibration of detection efficiency.     

基于Micromegas探测技术的中子CT可行性研究(英文)

在培育新品种过程中能够实时掌握了解土壤中植物根系的形态以及其生长情况将为植物学家提供很多不可或缺的信息。对基于 micromegas 探测技术的中子 CT 在这一新应用的试验环境进行了仿真模拟, 通过三维图像重建后,得到了令人满意的预期结果。首先通过 Geant4 和 Garfield 模拟计算利用聚乙烯薄膜作为中子转换层的 micromegas 中子探测器, 得到了非常理想的位置分辨, 说明基于micromegas 探测技术建立中子 CT 照相系统的可行性。 然后利用MCNP仿真模拟14 MeV 中子CT 的实验环境, 最后由Matlab程序进行图像重建。In this paper, the possibility using micromegas(Micro Mesh Gaseous Structure) as neutron detector in 14 MeV neutron computed tomography(CT) has been simulated. The results show that the micromegas neutron detector has high spatial resolution and is a good candidate for neutron radiography. The three dimensional images of plant roots in soil are successfully and clearly obtained by the 14 MeV neutron CT with micromegas as a neutron detector. In the present simulation, MCNP is employed for 14 MeV neutron transport in the sample and Matlab for the 3 D photograph reconstruction.     

近距离n, γ混合脉冲辐射场中γ辐射探测技术

n, γ混合脉冲辐射场中, 在近距离、辐射强度低且中子辐射峰值比被测γ辐射峰值强度高的情况下, 传统γ辐射探测技术实施起来面临困难. 对PbWO4和CeF3等近年国内新研制的无机闪烁体进行了系列研究, 使用CeF3分别配光电倍增管和光电管,组合出了对γ辐射灵敏度高, 对中子相对不灵敏, 同时脉冲响应也快的光电探测系统, 应用以此为基础的探测技术在近距离n, γ混合脉冲辐射场中, 可将脉冲γ辐射探测信噪比提高一个量级以上. It is difficult to detect low intensity γ radiation by using traditional γ radiation detection technique in a close distance n, γ commix pulse radiation field with very high intensity neutron radiation. PbWO4 and CeF3 which are newly developed inorganic scintillator in our country have been studied. Photoelectricity detector systemes which have high γ sensitivity and relative insensitive to neutron and fast time response were assembled by using CeF3 and photomultiplier tube. The ratio of signal to noise for γ ray detection can be up to more than 10 times in close distance n, γ commix pulse radiation field by using this detector system.     

(n,γ)反应实验研究中的中子屏蔽设计

用射线全吸收型装置(Gamma-ray Total Absorption Facility,GTAF),可以对中子俘获反应截面进行高精度测量。为了降低实验本底,实验中需要对源中子进行准直和屏蔽,还要对被样品散射的中子进行吸收以减少它们进入探测器后所形成的干扰。采用MCNP对中子的准直器、屏蔽体和中子吸收体进行了模拟设计,中子准直屏蔽体材料选用含硼聚乙烯(BC4 的质量分数为3%) 和铅。准直孔直径为13 mm,长度为500mm,经准直后样品处中子束斑坪顶直径为21 mm。中子吸收体材料选用聚乙烯和碳化硼,吸收体球壳内腔半径30 mm,聚乙烯壳层厚度60 mm,碳化硼壳层厚度10 mm,被样品散射的中子经吸收体后衰减93.7%。Neutron capture cross section can be measured by Gamma-ray Total Absorption Facility (GTAF) with high precision. To reduce the background of experiments, the neutron source must be collimated and shielded, and the neutrons scattered from the sample must be absorbed to minimise interference after they go into the detector. The shield, collimator and absorber were simulated and designed with MCNP code. Boron-ontainingpolyethylene with 3% BC4 and lead are used as the materials for the neutron collimator and shield. The diameter of the collimating aperture is 13 mm, and the length of the collimator is 500 mm. After being collimated, the diameter of neutron beam plateau at the sample position is 21 mm. The neutron absorber is made of polyethylene and BC4, and the thickness of polyethylene shell and BC4 shell are 60 and 10 mm, respectively. The simulated result shows that neutrons scattered from the sample can decay 93.7% through the neutron absorber.     

2.8MeV中子诱发238U裂变的瞬发中子谱高能段实验测量

在中国原子能科学研究院的高压倍加器上利用中子飞行时间方法测量了2.8 MeV中子引起238U裂变的瞬发中子能谱,通过增大样品量和设计合适的屏蔽体提高了效应/本底比,使得测量数据的不确定度满足预期目标（在5.5～14 MeV能区内,能量间隔为0.5 MeV条件下能谱的不确定度小于10%）。将实验几何、中子源能量分布及角分布、探测效率、束流的时间结构等实验条件输入到MCNP程序里,模拟了出射的中子谱,模拟结果与测量结果在不确定度范围内一致,验证了在入射中子能量较低时238>U的裂变瞬发中子谱评价数据的可靠性。The Prompt Fission Neutron Spectrum (PFNS) of 238U induced by 2.8 MeV neutron was measured using the Cockcroft-Walton accelerator in China Institute of Atomic Energy (CIAE). The signal/background ratio was improved by increasing the amount of sample mass and using an appropriate shielding system. The final uncertainty of neutron energy spectrum in 5.5～14 MeV region is less than 10% with a bin size of 0.5 MeV which has reached this project's anticipation. The experimental geometry, the angular distribution and energy distribution of neutron source, the detection efficiency and time structure of deuteron beam were inputted into the MCNP code to simulate the outgoing neutron spectrum. The simulated results agree with the experimental ones within the uncertainty. The result indicates that the evaluated PFNS for 238U at low neutron energy is reliable.     

中子、γ射线在稀土-高分子材料中的输运(英文)

为研究新型复合屏蔽材料的最佳厚度与各种成分最佳配比, 用MCNP计算了中子、 γ射线在稀土 高分子与重金属复合材料中的通量。 对中子、 γ射线在屏蔽体中变化规律进行了深入探索, 同传统复合屏蔽材料的屏蔽性能进行了对比。 结果表明, 中子和γ射线通过屏蔽体时, 其强度遵循指数衰减规律。 新型屏蔽材料对中子的屏蔽效果均优于铅硼聚乙烯, 对γ射线的屏蔽效果均劣于W Ni合金, 且并非稀土含量越高, 材料对中子辐射屏蔽能力越强。 A series of shielding analyses have been performed to estimate the material composition and optimum thickness required for a new radiation shield with various rare earth doped polymer and heavy metal mixtures. The neutron and γ photon fluxes have been calculated by Monte Carlo N Particle(MCNP) transport code. The results indicate that the relative fluxes of γ photon and neutron in both traditional and new composite materials follow an exponential decay rule with the distance of penetration. It can be seen that the composite material consisting of rare earth doped polymer and heavy metal has stronger neutron shielding performance than lead boron polyethylene, but weaker γ shielding effectiveness than W Ni alloy. It is also found that materials with more components of rare earth elements don’t always provide better neutron shielding performance.     

基于D-T紧凑型中子源的快中子照相准直屏蔽体设计及中子束特性模拟研究

中子照相是一种重要的无损检测技术,它能用于火工产品、毒品和核燃料元件等的检测。基于紧凑型D-T中子发生器,完成了一个用于快中子照相的准直屏蔽体系统（BSA）的物理设计。根据D-T中子源的能谱和角分布建立了中子源模型,采用MCNP4C蒙特卡罗程序,模拟了准直屏蔽体系统中中子和γ射线的输运,准直中子束相对于单位源中子的中子注量可以达到9.30×10-6 cm-2,准直中子束中主要是能量大于10 MeV的快中子;在设置的样品平面直径14 cm的照射视野范围,准直束中子注量的不均匀度为4.30%,准直束中中子注量与γ注量的比值为17.20,中子通量和中子注量比值J/Φ为0.992,说明准直中子束有好的平行性;准直屏蔽体外的泄露中子注量率与准直束中子注量率相比降低了2个量级。所设计的准直屏蔽体能满足快中子照相的要求。Neutron radiography is an important nondestructive testing technique. It can be used to detect the explosive devices, drug and the nuclear fuel element, etc. A beam-shaping-assembly (BSA) based on a compact D-T neutron generator is designed for fast neutron radiography in this paper. D-T neutron source model is constructed based on the neutron energy spectrum and angular distribution data. The transportation of neutron and γ-ray in the BSA is simulated using MCNP4C code. The neutron fluence of the collimated neutron beam with respect to the neutron source of the unit source is 9.30×10-6 cm-2. The collimated neutron beams is mainly fast neutrons with energies greater than 10 MeV. In the irradiation field range with a diameter of 14 cm, the neutron fluence uniformity of the collimated beam is 4.3%, the ratio of the neutron fluence to the gamma fluence in the collimated beam is 17.20, and the neutron flux and the neutron fluence ratio (J/Φ) is 0.992 which indicates that the collimated neutron beam has good parallelism. The leakage neutron fluence in outside of BSA is two orders of magnitude lower than that of the collimated neutron beam. The designed BSA can meet the need of fast neutron radiography.     

LS301快中子探测器的效率刻度

主要介绍了利用252Cf标准裂变中子能谱刻度快脉冲LS301型液闪中子探测器的探测效率的实验方法和结果, 简要介绍了实验数据的处理过程, 得到了阈值分别为0.5, 0.7, 1.0和1.6 MeV, 以及中子能量在10 MeV以下的探测器效率, 并对测量结果进行了误差分析。同时为了检验实验结果的准确性, 将实验结果与理论计算结果进行比较, 两者在不确定度范围内符合得很好。Neutron detection efficiency of LS301 fast neutron detector was calibrated by measuring the neutron energy spectrum of 252Cf source, which has a standard fission neutron spectrum. A low mass, fast ionization chamber is used as the fission fragments detector in the time of flight(TOF) spectrometer and afforded the start signal of neutron flight. The stop signal was offered by the anode of LS301. A measured TOF spectrum was turned to the neutron energy spectrum which will be compared with the standard one. Consequently, the fast neutron detection efficiency of LS301 was obtained. Calibration procedures of experimental and data processing was given. Relative detection efficiencies were obtained separately for threshold settings of 0.5, 0.7, 1.0 and 1.6 MeV for neutron energies under 10 MeV. Experimental results accorded with theoretical efficiency curves which were calculated with the Monte Carlo code NEFF50.     

Design and gamma sensitivity measurement of a novel dual-emitter vacuum Compton detector

A novel dual-emitter vacuum Compton detector (D-VCD) with higher gamma ray detecting efficiency is proposed. The emitters are made of Ta--Al clad metal. The gamma ray sensitivity is studied by Monte Carlo simulation using the MCNP code. A comparison between calculations and results measured by using the 1.25~MeV gamma ray of Co-60 is also performed. Experimental sensitivities for two sample D-VCDs with the same materials and structures are 1.92×10^ - 20 and 2.02×10^ - 20~C.cm²/MeV separately, which are consistent with the simulation result of 1.98×10^ - 20~C.cm²/MeV and are 4 times higher than that of VCD with a single Fe emitter. According to the simulation results, in a gamma energy range from 0.5 to 3~MeV, the maximum sensitivity variance for the D-VCD is less than 15%, and less than 5% in a range from 1 to 2~MeV in particular. The novel D-VCD is applicable to the detection of intense pulse gamma rays.     

Determination of neutron capture cross sections of ~(232)That 14.1 MeV and 14.8 MeV using the neutron activation method

The ~(232)Th(n,γ)~(233)Th neutron capture reaction cross sections were measured at average neutron energies of 14.1 MeV and 14.8 MeV using the activation method.The neutron flux was determined using the monitor reaction~(27)Al(n,α)~(24)Na.The induced gamma-ray activities were measured using a low background gamma ray spectrometer equipped with a high resolution HPGe detector.The experimentally determined cross sections were compared with the data in the literature,and the evaluated data of ENDF/B-Ⅶ.1,JENDL-4.0u+,and CENDL-3.1.The excitation functions of the ~(232)Th(n,γ)~(233)Th reaction were also calculated theoretically using the TALYS1.6 computer code.     

个人中子剂量气泡探测器研制

中子固体气泡探测器被认为是唯一能够满足国际辐射防护委员会ICRP60要求的个人中子剂量计，它具有从低能中子到高能中子的平坦响应曲线和对γ射线不灵敏的优点.本工作将过热液滴均匀地分布在一种软聚合物中，制成了个人中子气泡剂量计,其灵敏度达到每毫雷姆40个气泡.还介绍了个人中子剂量气泡探测器的原理和制作过程.Neutron solid bubble detector was considered as a unique one for meeting the need of the personal neutron dosimeter recommended by International Committee of radiation protection,ICRP60.It has the flat response for neutron from low energy to high energy,and insensitive for gamma rays. In this work,superheated liquid drops were dispersed into a kind of soft polymer homogeneously.A personal neutron bubble dosimeter has been made,and the sensitivity reached to about 40bubbles/mrem.The principle and the processing procedure of bubble detector were also introduced in this paper.     

用于中子测量的俘获探测器研究

为了在弱中子场和有限小空间内测量绝对裂变率, 制作了俘获探测器, 研究了俘获探测器的性能。 介绍了用于中子测量的俘获探测器和铅屏蔽室, 以及该探测器系统在特定条件下测量裂变反应率的结果, 并与裂变室测量结果进行了比较。 探讨了铅屏蔽室大小对测量结果的影响。 To detect the absolute neutron flux in a weak neutron field and restricted space, the fission fragment trapping detector was fabricated and the properties of the detector were studied. In this paper, the detector and shielding chamber used in neutron detection were described and the experimental measurements of the fission rate in specific condition were performed with the detection system and the result has been compared with that obtained by fission chamber. The influence of the shielding chamber on the measured results was analyzed.     

（n,xnγ）反应截面测量的实验本底改进研究

瞬发γ射线法测量（n,xnγ）反应截面实验中,在线的实验本底对测量结果影响显著,是影响测量结果的关键因素。为了达到降低在线实验本底一个量级的目标,通过蒙特卡罗模拟程序给出了屏蔽体和准直器的改进方案,最终选取的屏蔽方案:在原有屏蔽体上加厚30 cm（C₂H₄）n+9 cmPb,原屏蔽墙加厚54 cm重混凝土,再在屏蔽体和屏蔽墙上共同加厚2 cm厚的铅（Pb）;准直孔开孔形状在圆柱形、圆锥形和对称双锥形这三种方案中准直效果和能量单一性方面对称双锥形准直孔最好。在屏蔽体改造完成后,利用尺寸为φ5.08cm×5.08 cm型液体闪烁体探测器（BC501）测量了改造后距准直孔右方径向距离70 cm处透射出来的中子和γ射线的相对强度,在扣除无束流天然本底后,有束流的中子本底降低了7.75倍,γ本底降低了38.5倍,改造效果达到了测量要求。In the experiment of measuring (n,xnγ) reaction cross section with prompt γ ray method, the experiment background has a significant influence on the result and is the key factor. In order to achieve the goal of reducing a certain amount of the experiment background, the improvement scheme of shield and collimator was given through Monte Carlo method and the shielding scheme was finally selected: add 30 cm(C₂H₄)n+9 cm Pb on the original shield, 54 cm heavy concrete on the original shield wall and then 2 cm thick lead(Pb) on the shield and shield wall. The collimation effect and energy uniformity of symmetrical double cone collimation hole are the best among cylindrical, conical, and symmetrical double cone. After the completion of the transformation of shield, the relative intensities of the transmitted neutron and γ rays from the 70 cm in right radial of the transformed collimation hole were measured with ?5.08 cm×5.08 cm type liquid scintillator detector(BC501). After deducting the natural background of no beam current, the neutron background of the beam current is reduced by 7.75 times and the γ background is reduced by 38.5 times, which meets the requirement.     

8.19 MeV中子与9Be作用的次级中子双微分截面测量

用中国原子能科学研究院HI13串列加速器上的多探测器快中子飞行时间谱仪, 测量了8.19 MeV中子与9Be作用时, 从20°到160°区间26个角度的次级中子双微分截面。测量截面以np散射截面作为标准进行归一。实验结果用Monte Carlo方法进行了中子注量率衰减、多次散射和有限几何修正, 并用MCNP4C程序对所用的Monte Carlo程序进行了验证。测量结果与评价数据以及其它实验室的数据进行了比较。The secondary neutron emission double differential cross section of 9Be induced by 8.19 MeV neutron was measured at 26 different angles from 20°to 150°by using the multi detector fast neutron TOF spectrometer at the HI 13 Tandem Accelerator at China Institute of Atomic Energy(CIAE). The results were normalized to np scattering measurement. A special Monte Carlo code which was validated with the MCNP 4C code was employed to analyze the measured data for the corrections of neutron flux attenuation, multiple scattering and finite geometry. The measured results were compared with the evaluated data and the other measurements.      

D-D 中子发生器n-γ 密度测井的蒙特卡罗模拟研究

根据D-D 反应中子的能谱和角分布数据,建立了中子源模型;根据石灰岩地层标准刻度井群数据,建立了井模型。采用MCNP 程序模拟了井中中子和γ 射线的输运,得到了不同地层密度和不同源距处NaI 探测器中的混合γ 射线能谱和非弹γ 射线能谱。在混合γ 射线能谱2.5~5.0 MeV 能区开窗,研究了开窗区混合γ 射线相对计数随源距的变化关系,确定源距应选择在30~80 cm 范围,给出了密度与混合γ 射线计数之间的非线性关系。研究表明,可以利用D-D中子源的混合γ 射线能谱来实现n-γ 密度测井。A D-D neutron source model was developed according to the neutron spectrum and the neutron angular distribution of D-D reaction. A standard calibration well model was built. The transports of the D-D neutrons and γ-rays in the well were simulated using MCNP code. The mixed γ-spectra and inelastic γ-spectra in the NaI detector were obtained for both different distances from a neutron source and different densities. Mixed γ count in the energy range of 2.5 to 5.0 MeV as a function of distance shows that the NaI detector should be located at a distance of 3080 cm from the neutron source. The nonlinear relationships between the density and the mixed γ count were presented in this paper.It was demonstrated that the energy spectrum of mixed γ rays can realize the n-γ density logging.     

应用于热中子的nTHGEM探测器性能研究

随着脉冲强流中子源的发展,对高性能中子探测器提出了更大的挑战,3He气体资源严重短缺和高计数率中子探测器的迫切需求,已开始制约着中子源应用技术的发展。中国科学院高能物理研究所针对中子的特殊性,专门研发了一种陶瓷基材的nTHGEM（neutron Thick Gaseous Electron Multiplier）探测器用于中子探测。基于nTHGEM的中子探测器具有高计数率、高位置与时间分辨能力、增益大、制作工艺简单,且便于大面积制作的特点,是目前国际上发展替代3He探测技术的重要方向之一。为了详细研究nTHGEM探测器的本身性能,本工作使用55Fe放射源研究了nTHGEM探测器的增益、计数率稳定性、能量分辨率等关键参数与nTHGEM膜间电压、收集场强、漂移场强之间的关系,优化了nTHGEM探测器在不同工作气体中的工作参数,为后续进一步优化nTHGEM探测器设计和工艺奠定了基础。实验结果表明,单层nTHGEM探测器在Ar（90%）+CO₂（10%）混合气体中增益能达到103,探测器计数率稳定性良好。另外,还在中国原子能科学研究院的CARR反应堆（China Advanced Research Reactor）上进行了中子束流实验,通过狭缝测量到探测器位置分辨率为（3.01±0.03）mm（FWHM）,已经接近高气压3He MWPC中子探测器水平。With the development of pulsed intense neutron source, the high-performance neutron detector poses more challenges. The severe shortage of 3He gas resources and the urgent need of neutron detector with high counting rate have begun to restrict the neutron source application technology development. In response to the particularity of neutrons, the Institute of High Energy Physics of CAS developed a nTHGEM(neutron Thick Gaseous Electron Multiplier)of ceramic substrate for neutron detection. The neutron detector based on nTHGEM is one of the most important directions for the development of alternative 3He detection technology in the world at present because of its high counting rate, high position and time resolution, large gain, simple fabrication process and large area production. In order to study the properties of nTHGEM detector in detail, this paper studied the relationship between nTHGEM detector's gain, counting rate stability, energy resolution and other key parameters and nTHGEM film voltage, collection field strength and drift field strength using 55Fe radioactive source, Optimized the working parameters of nTHGEM detector in different working gases, which laid the foundation for further optimization of nTHGEM detector design and process. The experimental results show that the single-layer nTHGEM detector has a gain of 103 in a Ar(90%)+CO₂(10%) mixed gas with good counting rate stability. In addition, a neutron beam experiment was performed on the China Advanced Research Reactor at the China Institute of Atomic Energy, and the position resolution of the detector was (3.01±0.03) mm (FWHM) measured by slits. Its performance is close to the high pressure 3He MWPC neutron detector level.     

NaI探测器对23.8 MeVγ射线的效率刻度方法

低能D(d,γ)4He辐射俘获反应截面的研究在聚变领域和天体物理等领域中起到非常重要的作用。由于受到标准γ源能量的制约,在研究D(d,γ)4He反应高能γ射线产额实验过程中不能用标准源进行效率刻度。采用实验测量与计算相结合的方法实现NaI探测器对23.8 MeV γ射线的效率刻度,先对6.13MeVγ射线效率进行实验刻度,然后用蒙卡程序MCNP－4C模拟计算出NaI探测器的效率曲线,再用实验数据与模拟结果进行对比校正,计算出NaI探测器在23.8MeV能量点对γ射线的探测效率。该方法对高能γ射线效率刻度给出了一种参考依据。In the study of D(d,γ)4He radiative capture reactions research, which is very important for fusion and astrophysics, the efficiency calibration of the detector is necessary. Due to the restriction on energy of the standard gamma source, the efficiency calibration of high-energy gamma-rays can not be calibrated by a standard source. In this paper, the method combining the experimental measurements and calculations for the efficiency calibrations of high energy gamma rays is given in the experiment of 6.13MeV gamma rays efficiency calibration using NaI detector, the efficiency curve of which is calculated by MCNP-4C and corrected experimentally. In this case, the detection efficiency of 23.8MeV gamma ray is known. The method provides a reference to high energy gamma ray efficiency calibration.     

碳离子肿瘤治疗中弹核碎裂反应测量系统的研制

为了评估弹核碎裂反应在碳离子肿瘤治疗中产生的影响,中国科学院近代物理研究所建立了一套探测器系统用来测量相关反应产物。这套探测系统包括起始探测器、水靶系统、带电粒子鉴别系统和中子测量系统。利用中国科学院近代物理研究所250 MeV/u 12C6+ 束打50 mm水靶的实验在束测试了这套系统的性能。实验结果表明,通过ΔE-E 和TOF-ΔE 两种粒子鉴别方法这套探测系统清楚地区分了H,He,Li,Be,B和C 等元素。通过计算不同Z 值带电碎片的微分截面得到了这些带电碎片(本工作给出元素H 和He)相应的角分布。这套探测系统中的带电粒子测量系统性能达到了设计的预期目标。For estimating the influence of the projectile breakup reaction on carbon ion tumour therapy, a detector system was built by IMP(Institute of Modern Physics), Chinese Academy of Sciences(CAS), and used to detect the results of the reaction. The system is composed of start detector, water target system, charged fragments detector system and neutron detector system. The performance of the detector system was tested in the experiment of 5 cm thick water target bombarded by 250 MeV/u carbon beam. The results reveal that the charged fragments, such as elements H, He, Li, Be, B and C, were identified clearly by ΔE-E and ΔE-TOF techniques. The angular distributions of some charged fragments were obtained by calculating the charge-changing cross-sections of the fragments(e.g. elements H and He isotopes in our work). The test results prove that the charged fragment detector system achieves the design aim.     

Study on spatial resolution of micromegas as a neutron detector under condition of high neutron flux and γ ray background

In this paper Micromegas has been designed to detect neutrons. The simulation of the spatial resolution of Micromegas as neutron detector is carried out by GEANT4 toolkit. The neutron track reconstruction method based on the time coincidence technology is employed in the present work. The influence of the flux of incident 14 MeV neutron and high gamma background on the spatial resolution is carefully studied. Our results show that the spatial resolution of the detector is sensitive to the neutron flux, but insensitive to the intensity of γ background if the neutron track reconstruction method proposed by our group is used. The γ insensitivity makes it possible for us to use the Micromegas detector under condition which has high γ-rays background.     

位敏型探测器数字法读出研究(英文)

中国散裂中子源( CSNS ) 的建造对中子探测器提出了非常高的要求,如更大的有效面积、二维位置灵敏、高计数率、高探测效率和低的 灵敏度等。与传统的模拟读出方法相比,数字法读出具有更高的计数率, 更小的数据传输量,更简单的电子学设计以及更高的信噪比。对数字法读出进行了理论计算,利用GEM探测器的原始数据分析了数字法读出的位置分辨率与读出条宽度的关系。结果表明,数字法读出对于位置分辨要求较低( 小于4 mm) 的大面积位置灵敏探测器是一种较好的选择,如CSNS 小角谱仪探测器。Efficient thermal neutron detectors with large area, two-dimensional position sensitive, high counting rate high detection efficiency and low gamma sensitivity are required to satisfy the demands for the China Spallation Neutron Source (CSNS). Compared with the traditional analog readout method, the digital readout method has the advantages of higher counting rate, smaller quantity of data transmission, simpler readout system and higher signal to noise ratio. The theoretical analysis of the digital readout method is reported in this paper. Used the raw data of GEM detector, the relationship between the position resolution and the width of the readout strip was studied. The results indicate that the digital readout method could be a good choice for the large area position sensitive detector where the requirement of position resolution is less than 4 mm, e.g. the detector of Small-Angle Neutron Scattering (SANS) diffractometer of CSNS.