基于4H-SiC的高能量分辨率α粒子探测器北大核心CSCD

为突破传统半导体核探测器耐高温与抗辐照性能不足的瓶颈,采用4H-SiC宽禁带半导体材料研制了4H-SiC探测器,并研究其构成的探测系统对α粒子的能量分辨率和能量线性度。所研制4H-SiC探测器漏电流低,当外加反向偏压为200V时,其漏电流仅14.92nA/cm2。采用具有5种主要能量α粒子的226 Ra源研究其构成的探测系统对α粒子的能量分辨率,获得4H-SiC探测系统对4.8~7.7 MeV能量范围内α粒子的能量分辨率为0.61%~0.90%,与国际上报道的高分辨4H-SiC探测系统能量分辨率一致。同时,实验结果表明：4H-SiC探测系统对该能量范围内α粒子的能量线性度十分优异,线性相关系数为0.999 99。     

4H-SiC探测器的γ辐照影响研究

为研究4H-SiC探测器的抗γ辐照性能,使用40万Ci级的60Co源对4H-SiC探测器进行了数次辐照,累积辐照剂量最大为1 MGy(Si),并在辐照后对4H-SiC的性能进行了测试。随着累积辐照剂量增加,4H-SiC探测器的正向电流增大,而反向电流恰好相反;根据4H-SiC探测器的正向I-V曲线可提取理想因子和肖特基势垒,理想因子从1.87增加到2.18,肖特基势垒从1.93 V减小至1.69 V;4H-SiC探测器对241Am源产生的α粒子进行探测时,探测器的电荷收集率从95.65%退化到93.55%,测得能谱的能量分辨率由1.81%退化到2.32%。4H-SiC探测器在受到1 MGy(Si)的γ辐照后,与未受到辐照时相比,在探测能量为5.486 MeV的α粒子时能量分辨率和电荷收集率仅退化了28.18%和2.2%,仍具备优良的探测性能。     

4H-SiC肖特基二极管的电荷收集特性

针对极端环境下耐辐照半导体核探测器的研制需求,采用耐高温、耐辐照的4H碳化硅(4H-SiC)宽禁带材料制成肖特基二极管,研究了该探测器对241Am源粒子的电荷收集效率。从电容-电压曲线得出该二极管外延层净掺杂数密度为1.991015/cm3。从正向电流-电压曲线获得该二极管肖特基势垒高度为1.66 eV,理想因子为1.07,表明该探测器具备良好的热电子发射特性。在反向偏压高达700 V时,该二极管未击穿,其漏电流仅为21 nA,具有较高的击穿电压。在反向偏压为0~350 V范围内研究了该探测器对3.5 MeV 粒子电荷收集效率,在0 V时为48.7%,在150 V时为99.4%,表明该探测器具有良好的电荷收集特性。     

新型大面积Si-PIN探测器的研制

采用平面工艺制备了大面积Si-PIN探测器,探测器厚度300μm,直径分别Φ50mm、Φ60mm。在室温环境下测量了探测器的漏电流及226 Ra-α粒子能谱响应。结果表明大面积Si-PIN探测器具有耐压能力强、漏电流小、能量分辨率高等优点,能够满足核辐射探测领域的相关应用。     

基于4H-SiC肖特基势垒二极管的γ射线探测器

针对极端环境下耐高温和耐辐照半导体核探测器的研制需求,采用外延层厚度为100μm的4H碳化硅(4H-SiC)制备成肖特基二极管探测器,研究了该探测器对~(241)Am源γ射线的能谱响应.采用磁控溅射金属Ni制备了肖特基二极管的欧姆接触和肖特基接触,利用室温电流-电压和电容-电压测试研究了二极管的电学特性.欧姆特性测试表明,1050°C退火时,欧姆接触特性最好.从正向电流-电压曲线得出二极管肖特基势垒高度为1.617 eV,理想因子为1.127,表明探测器具备良好的热电子发射特性.从电容-电压曲线获得二极管外延层净掺杂浓度为2.903×10~(14)cm~(-3),并研究了自由载流子浓度在外延层中的纵向分布.在反向偏压为500 V时,二极管的漏电流只有2.11 nA,具有较高的击穿电压.测得在-300 V条件下,SiC二极管探测器对能量为59.5 keV的γ射线的能量分辨率为9.49%(5.65 keV).     

金刚石膜α粒子探测器的电学性能研究

从外加偏压、预辐照处理等方面对三明治结构金刚石膜探测器在α粒子辐照下的电学性能进行了研究.电流-电压特性和脉冲高度分布测试和分析表明，金刚石膜探测器在能量为5.5MeV的²⁴¹Am α粒子辐照一定时间后，其暗电流有所增加.探测器顶电极施加负偏压时，在α粒子辐照下得到的净电流和信噪比均较大.Raman光谱测试表明，造成上述现象的原因很可能是金刚石膜厚度方向的不均匀性分布.负偏压下探测器对α粒子的能量分辨率为25.0%，优于正偏压下的能量分辨率(38.4%).随着α粒子辐照时间的延长，探测器的净电流和电荷收集效率均有明显增加. 关键词： 金刚石薄膜 辐射探测器 电学性能 脉冲高度分布     

单光子超导探测器

 电荷耦合器件CCD已经成为天文学中经常使用的光学探测器,它对光子有很好的线性响应,在某些波长范围内非常有效.但是随着波长的减小,其探测效率越来越低,并且缺少本征频率和时间分辨率.在半导体CCD探测器中,光子的能量和激发态能量相当,因此不可能探测单个光子,也得不到光谱信息.     

SiC-pn结二极管α粒子辐射效应

为了研究6HSiC材料制作的pn结二极管探测器的辐照特性,采用蒙卡程序模拟研究了4.3和1.8MeV能量的α粒子在辐照探测器中的物理过程。介绍了二极管探测器的工艺制作和物理参数,根据其结构建立了仿真模型,利用蒙卡程序进行了α粒子照射的仿真研究。研究结果直观地反映了α粒子在探测器中的输运情况。α粒子在探测器中的辐射效应主要是电离作用,电离产生的电子空穴对形成一定的分布。给出了α粒子在探测器中的电离能量损失分布及二极管探测器的电荷收集效率表达式。     

高性能PIN-硅探测器的研制及其在高能放射性核束实验中的应用测试

鉴于国内核物理实验对高性能硅探测器有大量需求,而国外对中国进行技术封锁,满足实验需求的高性能探测器不易获得.中国科学院近代物理研究所在原有制备工艺基础上首次采用套刻技术,有效减少了光刻及腐蚀过程造成的Si O2沾污,大幅提高了探测器性能和成品率.本文对采用该工艺研制的300μm厚,有效面积50 mm×50 mm硅探测器进行电学性能测试和在束探测性能测试.探测器在–45 V耗尽电压下,其漏电流小于40 n A,对5 Me V左右的a粒子的能量分辨(σ)约为45 ke V.将该探测器作为能量沉积(ΔE)探测器,利用250 Me V/u的¹¹C放射性束流及其在次级碳靶上的反应产物对探测器进行了探测性能测试.测试结果显示,该探测器对于C元素的电荷数Z的分辨为0.17,与文献中记录的国外生产的同类型探测器的实验数据(Z分辨0.19)相当,可以满足中高能放射性束实验对轻质量区粒子鉴别的要求.     

MRPC-TOF时间性能和刻度方法的研究

研制的由28个多气隙电阻板室(MRPC)模块构成飞行时间探测系统, 从2003年以来在RHIC-STAR实验上成功运行并获得了大量的实验数据. 为了深入了解MRPC实际运行中的性能,采用质心能量200GeV的Au-Au对撞的实验数据, 对MRPC-TOF的刻度方法进行了深入研究, 主要包括: (1) 对现有的刻度方法做了进一步的改进; (2) 对粒子入射角度等因素进行了修正; (3) STAR径迹重建的位置分辨率对MRPC时间分辨率影响. 用改进后的刻度和修正方法, 计算得到MRPC的本征时间分辨率为大约60ps, 与束流实验结果相近.     

Si-PIN与CdTe探测器应用于X射线荧光能谱测量的研究

半导体探测器具有优异的性能因而被广泛应用于能量色散X射线荧光测量,以传统型Si-PIN半导体探测器与复合型CdTe半导体探测器为研究对象,分别从材料属性、探测效率、能量分辨率等方面对两种探测器进行对比,重点分析探测器灵敏区厚度、入射X射线能量、后级电路成型时间等因素对其性能的影响,并对由逃逸峰、空穴拖尾效应所导致的X射线荧光能谱的差异进行分析;同时,针对探测器空穴收集不完全的问题,基于FPGA设计了带有上升时间甄别功能的数字多道脉冲幅度分析器,能够有效消除空穴拖尾的影响,提高能量分辨率。从实验结果可知:对能量低于15keV的射线,Si-PIN与CdTe探测器的探测效率基本相当;对能量大于15keV的射线,CdTe探测器的的探测效率明显占优;Si-PIN探测器的最佳成形时间约为10μs,CdTe探测器的最佳成形时间约为2.6μs,因而CdTe探测器更适用于高计数率条件;对于不同能量的X射线,Si-PIN探测器的能量分辨率优于CdTe探测器;CdTe探测器具有明显的空穴拖尾效应,将CdTe探测器与带上升时间甄别功能的数字多道脉冲幅度分析器配合使用,其能量分辨率显著提高。     

Optoelectronic Devices: Design,Modeling, and Simulation,by Xun Li

A historical survey of the development of solid-state detectors is given, and it is shown why semiconductor detectors are superior to the earlier crystal counters. The physical processes which occur during the detection of nuclear radiation in a solid-state device are considered in detail, and the merits of the reverse-biased semiconductor junction in silicon or germanium are set out. Factors which determine the energy resolution of such a detector are analysed, and also the effects of radiation damage. The preparation of such detectors is not treated in detail, but the physical principles on which the important types of detector depend are described. The final section surveys the field of applications of solid-state detectors in nuclear physics, radiochemical analysis, space research, medicine and biology.     

CdZnTe像素探测器的电输运性能

碲锌镉(CdZnTe)是一种性能优异的室温核辐射半导体探测器材料,广泛应用于核安全、核医学以及空间科学等领域.然而,传统的CdZnTe平面探测器受制于"空穴拖尾"效应的影响,探测性能有待改善.采用改进的垂直布里奇曼法生长的In掺杂Cd_(0.9)Zn_(0.1)Te单晶制备出单载流子收集的4×4像素阵列探测器,通过电流-电压(I-V)测试和γ射线能谱响应测试,研究了像素探测器的电学性能和载流子电输运性能,随之与相应的CdZnTe平面探测器进行了性能对比.结果表明,CdZnTe像素探测器的电阻率约为1.73×10~(10)?·cm,且施加100 V偏压后单像素点的最大漏电流小于2.2 nA;当施加偏压升高至300 V时,单像素点对~(241)Am@59.5 keV的γ射线的最佳能量分辨率可达5.78%,探测性能优于相同条件下制备的CdZnTe平面探测器.     

A telescope for α-particle spectrometry

An alpha spectrometer based on a telescope consisting of two silicon semiconductor surface barrier detectors is described. The spectrometer has been used to study the α-particle energy spectra of an (n,α)-type reaction and ternary fission of uranium in an energy range 4–30 MeV with a resolution of 85 keV.     

Particularization of alpha contamination using CR-39 track detectors

Solid-state nuclear track detectors have found wide use in various domains of science and technology, e.g. in environmental experiments. The measurement of alpha activity on sources in an environment, such as air is not easy because of short penetration range of alpha particles. Furthermore, measurement of alpha activity by most gas ionization detectors suffers from high background induced by the accompanying gamma radiation. Solid state nuclear track detectors (SSNTDs) have been used successfully as detecting devices and as a passive system to detect alpha contamination on different surfaces. This work presents the response of CR-39 (for two types) to alpha particles from two sources, ²³⁸Pu with energy 5 MeV and ²⁴¹Am with energy 5.4 MeV. The methods of etching and counting are investigated, along with the achievable linearity, efficiency and reproducibility. The sensitivity to low activity and energy resolution are studied.      

Investigation of the processes of heat propagation in W/FeSb<Subscript>2</Subscript>/W detection pixel of the single photon thermoelectric detector

The results are presented of the computer modeling of the processes of heat propagation in the single layer detection pixel of the thermoelectric single photon detector after the absorption of photon with the energy of 1–1000 eV. The different geometries of the detection pixel consisting of the tungsten absorber and thermoelectric sensor from the strongly correlated FeSb₂ semiconductor are considered. The differences of temporal dependence of the signal appearing on the sensor for various size of the sensitive pixel elements are studied in detail. The energy resolution and the count rate of the detector are estimated. It is shown that the FeSb₂ sensor of thermoelectric detector provides the generation of significantly higher signal as compared with the CeB₆ sensor and has the perspectives of application in the single photon detectors with the high energy resolution.     

Dynamics of radiation induced quasiparticles in superconducting tunnel junction detectors

In order to achieve a high resolution in the spectroscopy of low energy X-rays, detectors based on superconducting tunnel junctions as sensors are presently investigated. The knowledge of the processes affecting the signal generation in such sensors is essential for the interpretation of the detector response. Starting from a diffusion model including decay and tunneling of excess quasiparticles in the metal layers of a superconducting tunnel junction detector, the detector response is determined as a function of absorption position and of rate constants. Model predictions agree very well with experimental data. The advantages of a detector employing quasiparticle trapping are pointed out and the parameters determining the signal gain are deduced. The linearity of the detector signal is much more affected by pair recombination of the quasiparticles during their tunneling rather than during their diffusive propagation into the tunneling region.     

HIRFL-CSR外靶终端上硅微条探测器阵列的搭建

硅微条探测器因具有很强的位置分辨率与能量分辨率而在世界各大核物理实验室得到广泛应用。中国科学院近代物理研究所研制了性能优越、位置精度达到0.5 mm×0.5 mm的双面硅微条探测器,用于HIRFL-CSR的外靶实验终端谱仪(ETF)上,用作径迹测量以及△E-E望远镜系统△E的探测。硅微条探测器体积小、集成度高,利用柔性印刷电路板(FPCB)引出信号,配合ASIC芯片的前端电路,能够方便地给出每一条的能量信息和位置信息。在此详细阐述了在HIRFL-CSR的ETF上双面硅微条探测器阵列的搭建,并测量了放射源在真空中探测单元的能量分辨本领。结果表明,该硅条探测器的每个探测单元对5~9 MeV能量的α粒子的能量分辨率在1%左右。