CR-39探测器对α粒子入射角度和能量响应的实验研究

为掌握固体径迹探测器CR-39对α粒子的入射角度和能量响应特性,通过建立1个可调节α粒子的入射角度和入射能量的241Am源照射系统,进行了不同入射角度和入射能量的α粒子照射CR-39探测器的实验研究,比较了不同照射条件下的径迹密度.实验结果表明,CR-39对α粒子的能量响应下限约为0.5 MeV,对入射角度响应的上限约为70°.本研究结果可为优化设计测氡的扩散杯(瓶)、提高其对氡的探测效率等提供科学的指导依据.     

CR39探测器对5种能量α粒子的响应

利用5种能量的α射线照射CR39探测器,采用浓度分别为6.0 N和6.25 N的NaOH溶液,在70℃的恒温条件下蚀刻,获得了体蚀刻率,蚀去厚度、径迹直径与蚀刻时间的关系,α粒子能量与径迹直径的关系等性能参数,为研究CR39对质子和中子的响应奠定基础。     

磁质子反冲谱仪磁分析器的设计与谱仪性能研究

设计一种用于紧凑型磁质子反冲(magnetic proton recoil,MPR)谱仪的小型单聚焦磁分析器,用钕铁硼二级永磁铁作分析磁铁,焦平面探测器为CR39。用实际磁铁的磁场分布数据和带电粒子输运程序分析磁分析器的性能,并用Pu-239α源实验标定。结合粒子输运程序的结算和蒙特卡罗模拟,研究了MPR谱仪的整体性能。结果表明:磁分析器能对3.5-8.5MeV范围内的质子和α粒子进行动量分析,有良好的动量色散和径向聚焦能力,符合紧凑型MPR谱仪的设计要求;对14MeV的DT聚变中子,谱仪有4%的能量分辨率和10-8的探测效率。     

基于CR-39固体探测器的粒子识别

为了掌握利用CR-39固体核径迹探测器识别α粒子和质子的方法,应用粒子与物质相互作用理论和径迹蚀刻动力学经验模型,模拟了α粒子和质子在CR-39固体核径迹探测器上的径迹形貌,计算出了3~8 MeV的α粒子和1~9 MeV的质子最佳蚀刻条件。根据对应的最佳蚀刻条件,计算获得的α粒子和质子的径迹直径、灰度值、径迹深度,并据此对相同能量的α粒子和质子、不同能量的α粒子、不同能量的质子进行识别。同时,采用CR-39固体探测器对α粒子(5.48 MeV)和质子(3 MeV)进行了实验测量,在模拟计算所获得的最佳蚀刻条件下,实验测读了α粒子径迹。实验测量得到的α粒子径迹直径与模拟值相差0.36%~9.70%。实验测量的最佳蚀刻时间和模拟的最佳蚀刻时间相差5.60%,这些结果验证了模拟方法的可行性。     

空间带电粒子能谱和通量分布探测的研究

采用金硅面垒探测器、CsI闪烁体和改进的快响应电子学系统 ,设计了一套空间带电粒子谱探测系统 ,包括ΔE E望远镜系统和数据的获取及处理系统。根据该空间粒子探测谱仪系统 ,提出了可同时或分别探测空间带电粒子能谱和通量的方法。可探测粒子的种类和能量分别如下 :质子 ,能量范围为1～ 2 0 0MeV ;α粒子 ,能量范围为 1～ 2 0 0MeV u ;氧离子 ,能量范围为 1 7～ 4 96MeV u ;铁离子 ,能量范围为 2 5MeV～ 1 0GeV u。     

A Particles' Direction Detector on Manned Space Ⅱ

针对空间带电粒子各向异性分布,不同的入射方向,粒子的通量有数个量级的差异,提出安装在二期载人航天目标飞行器上的新一代空间粒子探测器——空间粒子方向探测器.该仪器为我国最新研制的多功能、小型化空间带电粒子探测器,首次实现了高能电子、质子能谱探测及180°方向的粒子通量测量.通过监测轨道空间各种带电粒子的区域分布、方向分布和能谱分布,以及时空变化,从而获得完整的空间高能带电粒子的辐射图像,建立载人航天轨道静态和初步动态粒子辐射模型.     

通过改变Si(Au)探测器灵敏区厚度鉴别带电粒子的方法及应用研究

重点研讨通过改变探测器偏压,进而改变探测器的ＰＮ结（有效探测灵敏区）厚度,实验对带电粒子的种类和能量鉴别的实验方法及其实际应用。实验测量了３ＭｅＶ质子和６．０５ＭｅＶα粒子在金硅面垒探测器Ｓｉ（Ａｕ）中的能损与探测器偏压关系曲线。同时利用刻度过的探测器鉴别氚离子束轰击氚钛（ＴｉＤｘ）靶发射的带电粒子能谱。在很强的本底情况下通过调节探测器偏压（灵敏区厚度）实现了对能量相近的不同带电粒子的有效鉴别和测     

碳化硅与硅探测器辐射探测性能比较

碳化硅(SiC)材料因其禁带宽度大、晶体原子离位能高等物理特性,而被视为制作耐高温和抗辐射器件极具潜力的宽带隙半导体材料。本文采用Geant4模拟得到了30μm厚的SiC和Si材料对不同能量的电子、质子、α粒子以及X射线的响应,并对SiC和Si探测器器件的I-V特性和能谱测量结果进行了比较。仿真及试验结果证明,SiC粒子阻挡本领及X射线探测效率与Si探测器相当,SiC与Si探测器对带电粒子的能谱分辨率也没有明显差别。     

低能质子注入金属靶实验中的核现象研究

在低能（60－360keV）质子注入氚化钛（Ti^2Hx）、钛（Ti)、钼底衬 箔及钼（Mo）和不锈钢（SS）等金属样品的实验中,观测了能量分别约为3．9、5．6和8．4MeV的带电粒子物。用符合望远镜和吸收片法进行了粒子鉴别的结果表明：这些带电粒子均具有α粒子特性。3种α粒子来自质子与不同靶核发生的垒下核反应。其中,能量为3．9MeV的）α粒子具有很高的产额,其对应核反应的准激发函数曲线在150－330keV能区内,随入射质子能量增大呈指数增长趋势。上述反应产物可能源于^11N(p,α)^12C,^11B(p,α)^8Be和^7Li(p,α)^4He等核反应。但相关靶核的来源仍有待解释。利用扫描电子显微镜观测到有微球状的奇异形貌。     

固体径迹探测器CR39的标定

固体径迹探测器广泛应用于科学和技术方面,CR39是其中使用很频繁的一种塑料探测器。由于电子和伽马光子在CR39中的碰撞截面很小,远小于中子、质子或其他离子的碰撞截面,因此可认为固体径迹探测器CR39对电子和光子不响应,而仅对中子、质子或其他离子响应,这给CR39在实验中的应用带来很大优点。在超短超强脉冲激光与等离子体相互作用的实验中,会产生大量的强伽马射线、热电子或超热电子,而在有些实验如超短超强脉冲激光加速产生高能质子束的研究中,需单独对质子束的通量、角分布、能谱等参数进行详尽的测量。     

细胞尺度10B不均匀分布对细胞微剂量影响的计算与分析

硼中子俘获治疗已经成为当前治疗恶性黑色素瘤、头颈部肿瘤等恶性肿瘤的有效手段之一。¹⁰B在细胞尺度上不均匀分布将直接影响到对肿瘤细胞失活剂量的控制。为研究含硼化合物在细胞内空间上分布不同对靶区细胞微剂量的影响,本工作利用Monte-Carlo工具包开发了用于计算¹⁰B（n,α）⁷Li产生的α与⁷Li对靶区剂量的模拟程序α-Li Version 1.0。通过此程序,计算了2种细胞尺寸、8种α粒子能量、3种源分布方式的细胞S值,并与MIRD委员会解析算法的计算结果进行对比,两者差异在1%以内;对不同细胞核半径、不同细胞半径及不同源位置等条件下的3 420种模型进行了模拟计算,证明了α粒子和⁷Li粒子在细胞内的S值存在差异性;最终获得的¹⁰B（n,α）⁷Li反应的细胞S值数据库,可用于细胞尺度¹⁰B不均匀分布情况下的高精度微剂量学计算。     

CsI(Tl)探测器对带电粒子能量响应的入射位置依赖关系

在放射性核束物理的实验研究中,通常采用CsI(Tl)探测器对反应产物中的带电粒子进行总能量测量.使用GEANT4软件对CsI(Tl)闪烁体探测器能量响应通进行了蒙特卡罗模拟,在考虑了晶体外表面包覆材料反射率、耦合光敏二极管面积、射程等影响因素后,重点研究了CsI(Tl)闪烁体探测器对带电粒子能量响应的入射位置依赖关系....     

Improved modelling of helium and tritium production for spallation targets

Reliable predictions of light charged particle production in spallation reactions are important to correctly assess gas production in spallation targets. In particular, the helium production yield is important for assessing damage in the window separating the accelerator vacuum from a spallation target, and tritium is a major contributor to the target radioactivity. Up to now, the models available in the MCNPX transport code, including the widely used default option Bertini-Dresner and the INCL4.2-ABLA combination of models, were not able to correctly predict light charged particle yields. The work done recently on both the intranuclear cascade model INCL4, in which cluster emission through a coalescence process has been introduced, and on the de-excitation model ABLA allows correcting these deficiencies. This paper shows that the coalescence emission plays an important role in the tritium and ³He production and that the combination of the newly developed versions of the codes, INCL4.5-ABLA07, now lead to good predictions of both helium and tritium cross-sections over a wide incident energy range. Comparisons with other available models are also presented.     

基于真实细胞模型的低能α粒子辐照模拟研究

本文以人体上皮细胞为模版,利用Geant4、ROOT模拟α粒子能量沉积的微观过程和空间行为,对次级电子的产生及相互作用事件等进行描述,并针对细胞形态结构特异性,对不同能量、不同生物学分布、特定源 靶组合下α粒子在真实细胞体元模型中的微观剂量特征进行研究,获取了低能α粒子物理径迹结构、次级电子作用点的径向空间分布、次级电子能谱分布、单次事件比能分布、亚细胞S值等特征量。结合计算结果分析了α粒子在亚细胞水平上的微剂量学特征变化及影响规律,实现了对特定结构亚细胞水平微观剂量特征的定量描述。     

Submicron position-sensitive detector

A method has been developed to measure precisely the coordinates of charged particles incident between adjacent strips of a strip detector. The position sensitivity of an inter-strip gap has been studied by means of a pulsed laser beam and irradiation by -particles of a ²²⁶Ra-source. The capacitive division of charge generated by the incident particle depends on the position of its track. Its coordinates were determined by two-dimensional amplitude analysis of the charges collected by neighbouring strips. This method of coordinate determination applied to studies of spatial and energy distributions of electromagnetic as well as charged particle beams (including radioactive ion beams) of low intensity could provide the highest level of the precision limited by the track dimensions of charged particles, i.e. percents of a micrometer.     

基于三晶体耦合γ射线方向探测器的放射源定位

为了快速定位并寻回丢失的放射源,设计了一种由NaI、CsI、锗酸铋(Bi4Ge3O12,BGO)三种晶体与铅耦合组成的γ射线方向探测器,并采用基于蒙特卡罗方法的通用软件包MCNP(Monte Carlo N Particle Transport Code)研究了铅晶比例、射线能量、剂量率等因素对探测器角度分辨率的影响。结果表明,对于137Cs源,在空气吸收剂量率≥0.331μGy·h~(-1)处,定位角度偏差≤0.99°;对于60Co源,在空气吸收剂量率0.586μGy·h~(-1)处,测量的平均角度偏差为0.46°;对于水平距离7 m、高度4 m的3.7×107Bq 137Cs源,相对定位偏差约为5%。     

On the comparison of three methods of assessing beam quality for broad beam in vitro cell irradiation

The interaction of charged particles with living matter has recently attracted increasing interest in the field of biomedical applications such as hadron therapy, radioprotection and space radiation biology. Particle accelerators are particularly useful in this area.In vitro radiobiological studies with a broad beam configuration require beam homogeneity. The goal is to produce a dose distribution given to a cell population that is as close to uniform as possible.In this paper, we compare the results of three devices used to assess the beam quality for broad beam irradiation: a passivated implanted planar silicon (PIPS) particle detector, a position-sensitive solid state detector, which is camera-like, and a solid state nuclear track detector (CR39).The first device is a PIPS detector of 300 μm nominal depletion depth and an entrance window with a thickness of about 500 Å. It is collimated with a 0.5 mm aperture and mounted in air on an XY moving table as close as possible to the exit window of the beam line.The second device is a CMOS position-sensitive detector (technological process 0.6 μm AMS CUA), 112 × 112 pixels, with 153 × 153 μm² pixel size. It allows the user to rapidly obtain dose uniformity over a surface of 1 × 1 cm². During uniformity and dose rate assessment it is placed in air at the PIPS location.For both detectors, beam profile was obtained for various proton fluxes (from ∼5 × 10⁴ to 10⁶ particles cm⁻² s⁻¹). Preliminary tests were made with CR39 using 4 MeV He⁺⁺ ions.Results are analysed using Poisson distribution and cell hit probability.     

基于伴随粒子的快中子成像系统角分辨研究

不同于传统的快中子成像系统,采用伴随粒子成像技术无需机械准直即可消除大部分γ射线和散射中子的干扰,实现对厚重物体的高对比度成像。角分辨是影响系统成像质量的一项重要参数。通过理论分析,研究了入射离子的初始动量、靶点尺寸和探测器空间分辨等多个因素对系统角分辨的影响。利用基于GEANT4的模拟程序,计算了不同参数下被标记中子出射角分布的二维图像。分析及模拟结果表明,靶点直径和α探测器空间分辨率是影响角分辨的重要因素。为满足系统角分辨小于1°的设计目标,入射离子的初始动量变化范围应较小,靶点直径应小于1 mm,同时α探测器的空间分辨率应小于0.5 mm。     

基于Si-PIN探测器的电流型计数式α粒子测量

为解决基于Si-PIN探测器的传统计数型粒子测量系统在测量低强度脉冲辐射场时存在的计数率低和不能直接测量粒子时间信息的问题,提出了电流型计数测量方法。其原理是对电流型Si-PIN探测器在粒子入射时输出的脉冲信号进行线性放大和高速数字化,并使用数字信号处理算法进行数据分析以获得粒子测量信息。利用电流型Si-PIN探测器、电流型前置放大器和高带宽数字示波器组建了电流型计数测量系统,并在241 Am-244 Cm和239 Pu源上开展了α粒子测量实验。实现了脉冲幅度谱和粒子入射时间的联合测量,同时利用FIR及IIR型数字滤波器改善了能谱测量的能量分辨率。系统的最大计数率达2×106 s-1,适用于低强度脉冲辐射场测量。     

Resolution and sensitivity as a function of energy and incident geometry for germanium detectors

The use of modeling programs such as MCNP to predict the response of HPGe detectors is increasing in importance. Accurate simulation of germanium detectors to incident gamma rays relies on knowledge of the performance of the detector in different detector–source geometries. Two important performance parameters are the resolution and sensitivity. The resolution is the FWHM and FW.1M/FWHM ratio. The IEEE 325-1996 standard only specifies the FWHM measurement at one geometry and two energies. Nearly all measurements are made in a different geometry and at other energies. Other investigators [Specifications for Today’s Coaxial HPGe Detectors, 2001 ANS Annual Meeting, Milwaukee, WI; Metzger, private communication, see also: Radionuclide Depth Distribution by Collimated Spectroscopy, 2002 ANS Topical Meeting, Santa Fe, NM], have shown that the sensitivity and resolution change with position of the incident gamma ray on the front of the detector. Such variability has possible implications for the accuracy of peak shape and area determination, since the calibration is potentially a function of angle of incidence. To quantify the sensitivity and resolution variation as a function of energy and point of incidence, measurements have been made on several coaxial detectors of various crystal types and sizes in different source–detector geometries. The full-energy peaks from 59 keV to 2.6 MeV were used. The detectors were placed in a low-background shield to reduce any contribution from external sources. None of the detectors tested was a low-background type. The sources used were an ²⁴¹Am source, ⁶⁰Co source and a natural thorium oxide sample. The ²⁴¹Am 59 keV gamma rays were collimated by a 2 cm thick, 1 mm diameter lead collimator. Several gamma rays from the thorium source were used and collimated by a 10 cm thick and 2 mm diameter tungsten collimator. These collimated sources were used to collect spectra for the incident beam on the front and sides of the detectors. The peak widths were calculated using the methods outlined in IEEE 325-1996. Data are presented to show that the peak shape and sensitivity change with incident beam position and full peak energy.