Development of a Double Layered Scintillator for Separating and Detecting Low Energy Protons and Electrons

A scintillator system consisting of a thin (5,000 ? - 15,000 ?) CsI(Tl) layer evaporated onto a plastic scintillator (NE-102) has been developed for the purpose of distinguishing low energy protons from electrons and measuring the energy of each species. Evaporations in a high vacuum (10-8 Torr) produced layers of CsI(Tl) that scintillate with an efficiency comparable to optimally doped bulk material, If the CsI(Tl) layer thickness is 15,000 ?, it stops protons with energies below 170 keV and electrons with energies below 18 keV. Thus, protons with energies between about 25 and 250 keV can be distinguished from electrons with energies above 18 keV by examining the shape of the light pulse generated in the dual scintillator. Results obtained with protons and electron beams will be presented.     

The Response of Stilbene to Internally Generated Protons

A thick radiator neutron spectrometer has been constructed in which protons recoiling forward in the stilbene escape from the crystal and are detected in a silicon surface barrier counter. The coincident pulses from the two counters are recorded using a two-parameter analyzer. The instrument has been used to investigate (1) the response of stilbene to protons originating within the scintillator and (2) the behavior of the pulse shape discrimination as a function of the energy deposited in the stilbene crystal. The response function, which is required for the analysis of the neutron spectra, is compared with one obtained for protons incident externally on the same crystal. Small differences between the two response functions are observed and analyzed. Concerning the behavior of the pulse shape discrimination between protons and electrons it is found that, for internally generated protons, the ability to separate protons from electrons worsens as the energy deposited in the scintillator decreases. This contrasts with the behavior for protons which stop in the scintillator. The results support the hypothesis that the fast component of the pulse decreases with increasing stopping power whereas the slow component depends primarily on the energy lost. The results are analyzed and may be interpreted with certain assumptions to give the ratio of the fast and slow scintillation components.     

Activation of Structural Materials due to Recoil Protons in Light Water Reactor

The long-lived radioactivities of structural materials induced by recoil protons in BWR were estimated for land disposal of low level waste after reactor decommissioning. Reaction products of interest are ⁵³Mn, ⁹¹Nb, ⁹⁴Nb, ⁹⁷, Tc, ¹²⁵Sb, ¹⁷³Lu and ¹⁷⁴Lu. A method of calculating the proton spectrum in materials was presented. The program PEGASUS-P was developed by modifying the PEGASUS, a preequilibrium and multistep evaporation theory code, to calculate proton reaction cross sections. The proton-induced activities in stainless steel, Inconel and Zircaloy-2 were calculated under typical irradiation conditions in an operating BWR. It was shown that even the most dominant activity due to 91Nb from Zircaloy-2 did not exceed 1/1,000 of that of a typical neutron induced activity of ⁶³Ni for cooling up to 1,000 yr after the irradiation of 40 yr. The results are believed to hold for the case of PWR as well.     

Anisotropy of Scintillation Response of Anthracene to Neutron Generated Recoil Protons and Carbon Ions

The directional anisotropy in the scintillation response of an anthracene crystal to heavy charged particles was investigated. Energetic carbon and hydrogen ions were produced internally by scattering fast neutrons from the constituent nuclei. By use of a two detector coincidence system, the scintillations due to monoenergetic ions recoiling in a particular direction were selected and analyzed. The energies of the ions ranged from 2 to 3.5 MeV for the carbon recoils and from .9 to 7.3 MeV for the hydrogen recoils. Even though there was a wide variation in the average specific energy loss of the heavy charged particles considered, the magnitude of the anisotropy only varied between 39% for the carbon recoils and 20% for the 7.3 MeV hydrogen recoils. The measured hydrogen ion response in a particular direction as a function of energy was found to be approximately described by the formula suggested by Birks, dL/dE = (1 + kBdE/dx)-1, with kB being directionally dependent. The directional carbon ion response appeared to be a linear function of energy over the energy range investigated.     

100 MeV质子降能材料的选择研究

降能器对于提升质子单粒子效应（SEE）地面模拟试验的效率具有重要意义,而降能材料的选择是降能器设计中的首要问题。计算了100 MeV质子在4种常见降能材料铍、石墨、铝、铜中产生的能量岐离、角度岐离、中子本底以及感生放射性等对质子SEE地面模拟试验有影响的4个方面,其中感生放射性的计算中包含了降能过程在材料中产生的放射性核素种类、活度及残余剂量率。根据以上计算结果,并结合质子SEE地面模拟试验的要求,在降低相同的能量这一情况下,对4种材料作为100 MeV质子降能材料的适用性进行了分析比较,最终选择铝作为100 MeV质子的降能材料,并将应用在中国原子能科学研究院100 MeV质子回旋加速器的质子SEE地面模拟试验装置的降能器设计中。     

Energy and Angular Responses of the Criticality Accident Detector using a Plastic Scintillator

The Japan Atomic Energy Agency (JAEA), Nuclear Fuel Cycle Engineering Laboratories, operates a spent fuel reprocessing plant and MOX (Plutonium-Uranium Mixed Oxide) fuel fabrication plants. Criticality accident detectors have been installed in these facilities. The detector, the Toshiba RD120, is composed of a plastic scintillator coupled to a photomultiplier tube, and an operational amplifier. The alarm triggering point is set to 1.0–3.6 mGy.h^?1 in photon dose rate to detect the minimum accident of concern. However, a plastic scintillator is principally sensitive not only to primary photons but also to neutrons by secondary photons and heavy charged particles produced in the detector itself. The authors calculated energy and angular responses of the RD120 criticality accident detector to photons and neutrons using Monte Carlo computer codes. The response to primary photons was evaluated with the MCNP-4B and EGS4 calculations, and photon and X-ray irradiation experiments. The response to neutrons that produce secondary photons and heavy charged particles from neutron interactions was computed using the MCNP-4B and SCINFUL, respectively. As a result, reliable response functions were obtained. These results will be a great help in reassessing the coverage area and in determining the appropriate triggering dose rate level in criticality accidents.     

Proton Cyclotron Instability Threshold Condition of Suprathermal Protons by Kappa Distribution

Observation has clearly shown that natural space plasmas generally possess a pronounced non-Maxwellian high-energy tail distribution that can be well modeled by a kappa distribution. In this study we investigate the proton cyclotron wave instability driven by the temperature anisotropy （T⊥/TH 〉1） of suprathermal protons modeled with a typical kappa distribution in the magnetosheath. It is found that as in the case for a regular bi-Maxwellian, the supratherreal proton temperature anisotropy is subject to the threshold condition of this proton cyclotron instability and the instability threshold condition satisfies a general form T⊥/T｜｜ - 1 = S/β｜｜^α, with a very narrow range of the fitting parameters： 0.40 ≤ α ≤ 0.45, and a relatively sensitive variation 0.27 ≤ S ≤ 0.65, over 0.01 ≤β｜｜ 〈 10. Furthermore, the difference in threshold conditions between the kappa distribution and the bi-Maxwellian distribution is found to be small for a relatively strong growth but becomes relatively obvious for a weak wave growth. The results may provide a deeper insight into the physics of this instability threshold for the proton cyclotron waves.     

紧凑型磁质子反冲谱仪磁分析系统的能量刻度

介绍了一种用于多种特定环境下脉冲氘氚聚变中子能谱测量的紧凑型磁质子反冲谱仪的磁分析系统。通过三维粒子输运和蒙特卡罗模拟对磁分析系统性能进行了分析,使用CR-39径迹探测器和多个能量α单能粒子对系统进行了能量刻度。结果表明,磁分析系统具有良好的能量离散与聚焦性能,对给定能量范围的反冲质子,能够以1.5%~2.1%的能量分辨率实现（0.5~1.4）×10^－4的探测效率。     

脉冲中子全能谱测井闪烁探测器响应特性的蒙特卡罗模拟

利用蒙特卡罗方法模拟研究NaI和BGO晶体探测器对不同γ射线的响应。模拟结果表明,BGO晶体的光电峰和第一逃逸峰对计数贡献大,而NaI晶体的逃逸峰贡献大。对于井眼和地层流体分别为油和水砂岩地层,模拟改变NaI和BGO晶体探测器的直径和长度时的非弹性散射γ射线响应能谱,采用不同能窗处理方法对地层流体的分辨能力不同,选取光电峰和第一、第二逃逸峰对应的能量窗时,BGO晶体探测器比NaI晶体探测器测量的C/O（C与O的元素含量比）差值大,但受尺寸的影响不大;采用光电峰对应的能量窗时,BGO晶体探测器测量的C/O差值比NaI的大得多,且随尺寸的增加差值增大;能量道的漂移对C/O值影响较大,而能量分辨率对差值影响相对较小。     

Energy Spectra of Heavy Fragments from the Interaction of Protons with Communications Materials

A Monte Carlo computer code is used to calculate the energy spectra of recoil nuclei resulting from interactions of protons with communications materials. Results are presented for 130 MeV and 1 GeV protons incident on O, Si, Ga, As, and Au. The results for 130 MeV protons on Si are compared with previous calculations and measurements.     

氡子体α能谱真空测量RaB的反冲损失率

氡子体α能谱法测量时的真空度使RaB发生反冲损失,这会对氡子体测量精度产生影响并造成测量腔室的污染。本实验选用0.8 μm孔径的Millipore AA型滤膜,在流率为6.3、12.3和15.6 L/min下,使用ELPI粒径分析仪、α测量仪和α谱仪分别对氡室气溶胶粒径分布、滤膜自吸收系数及反冲损失率进行测量。结果显示：氡室内气溶胶浓度呈单峰分布;相应流率下的自吸收系数为0.978、0.980、0.989,反冲损失率为0.362 8、0.368 4和0.362 9;所得反冲损失率并未表现出较大的差异,但滤膜样品上由RaA衰变产生的RaB原子却有较大的反冲损失。     

用于在线测量反应堆内热中子相对通量密度分布的闪烁体光纤探测器研究

闪烁体光纤探测器采用双探头甄别中子信号,利用252 Cf裂变源对探测器系统进行了测试,并与3 He计数管的计数进行了对比。在启明星1#上进行了热中子相对通量密度分布的测量,结合Geant4得到的不同能量段的中子转化率及MCNPX模拟得到的反应堆中子能谱,对探测器进行了相对效率刻度,测试结果与固体核径迹探测器测得的裂变率分布进行了对比。测量结果表明,闪烁体光纤探测器对于252 Cf中子源的响应基本符合点源的衰减趋势,与3 He计数管的测量结果符合较好。在启明星1#热区测得的热中子相对通量密度分布与固体核径迹探测器测量到的结果一致,快区测得的热中子相对通量密度分布与3 He计数管的测量结果及MCNPX的模拟结果符合较好。测量结果为闪烁体光纤探测器的研究提供了较好的实验依据。     

Helium Production in Solid Target and Metallic Window Materials Irradiated with Intermediate and High Energy Protons

The helium isotope formation cross-section has been obtained for iron, tantalum and tungsten irradiated with protons at energies from the reaction threshold up to several GeV. The cross-section evaluation has been performed using the results of model calculations and by the analysis of available experimental data.

The numerical calculations were carried out using the modified ALICE code and the CASCADE/INPE code.     

用CR-39固体径迹探测器测量激光加速产生的100 keV以下的质子能谱

本文通过实验验证CR-39临界角是其不能探测到100 keV以下质子能谱的原因。并据此改进探测方案,利用CR-39和Thomson谱仪测得超强激光与5 μm厚Al靶作用产生的100 keV以下的质子能谱。探讨了利用单粒子模拟法处理Thomson谱仪的数据,该方法规避了谱仪中磁场边缘场对测量的影响,提高了谱仪测量精度。     

The Slow Component of Scintillation in Stilbene

Experimental study of the response of stilbene to protons (0,8 to 1,8 MeV) indicates a non-linearity in the intensity of the fast components vs energy and a linear relationship for the slow component. It was found for stilbene and anthracene a decreasing intensity of the slow component with increasing particle mass (electrons, protons, alphas). The temperature dependence of both components has been measured between -130°C and 20°C. A relative increase of the same magnitude, about 20 % has been observed for the fast and the slow emission at low temperature. This paper presents the experimental devices used in these experiments and a discussion of the results in relation to models proposed for the slow emission process (mainly triplet-triplet interaction).     

快响应束流损失监控(FBLM)系统液闪探测器初样的研制

给出快响应束流损失监控(Fast Beam Lost Monitor,FBLM)系统的液体闪烁体探测器初样的研制.在高频四极加速器(Radio Frequency Quadrupole,RFQ)实验装置上的测试表明,液闪探测器能给出宽度为500 μs 束流宏脉冲结构,能逐个显示出宏脉冲内490 ns的束流切束脉冲.液闪...     

Application of High Energy Protons in Inertial Confinement Fusion by Using the Fast Ignitor Concept for DT Fusion

A short-laser-pulse driven ion flux is examined as a fast ignitor candidate for inertial confinement fusion. The main mechanism for ion acceleration is charge separation in a plasma due to high-energy electrons driven by the laser inside the target. Another very new branch of fast ignition research is the investigation of the use of laser generated proton beams. In the present paper aims to provide insights into the feasibility of the fast ignition concept with high energy beams of protons generated in laser–plasma interactions. The optimum parameters of an ion beam and laser pulse that are suitable for an ignition spark in a hot precompressed DT fuel are estimated as a rough guide. Also, in this paper we estimate the radius of Deuterium–Tritium (DT) fuel pellet that is equal to the protons range in DT plasma.     

Development of New Thermal Neutron Scintillator Screen

<正>Neutron scintillators have found widespread application in the detection of thermal neutrons especially in neutron radiography.Although composite neutron scintillators based on ZnS:Ag fluorescent materials have been in use for many decades,there are still some points pertaining to be optimized to improve the detection efficiency