Wafer-Bonded Silicon Gamma-Ray Detectors

A wafer-bonded silicon power transistor has been shown to function as an x-ray detector. The device consists of two thin device wafers bonded onto either side of a 2 mm-thick high-resistivity silicon wafer. The hydrophobic bonding process was performed at 400deg C. This low temperature wafer bonding technique should enable the development of large-area, position-sensitive detectors, using thick, high-resistivity intrinsic silicon bonded to thin readout wafers fabricated using conventional CMOS technology. These devices should enable fabrication of thicker intrinsic silicon detectors than currently available. Thick, position-sensitive detectors based on double-sided strip detectors and pixellated detectors are possible. To demonstrate this, a 1 mm thick gamma-ray detector was created from two 0.5 mm thick wafers that were patterned with gamma-ray strip detectors. The energy resolution of the detector is 8.9 keV FWHM for 60 keV gamma rays at room temperature with a leakage of 0.9 nA while operating at 700 V and fully depleted. Improvements in the technique should allow for thicker detectors with better energy resolution.     

基于模拟点源测量的多针孔SPECT精确迭代重建

高分辨率单光子发射计算机断层成像（SPECT）是临床和小动物影像的重要技术之一。对SPECT的系统传输矩阵进行建模,并结合于迭代重建算法中,是提高系统空间分辨率的有效手段。本文基于实验室自主研发的多针孔小动物SPECT系统,研究了一种蒙特卡罗模拟和解析模型相结合的系统传输矩阵精确计算方法。该方法是基于多点源模拟的投影数据,结合数据再估计方法和高斯拟合方法提取点扩展函数（PSF）特征参数,并结合解析形式的系统物理模型,从而计算任意位置的精确PSF。通过对四点源模拟投影数据分别用纯解析方法和蒙特卡罗模拟与解析模型相结合的方法进行计算,并对所得的系统传输矩阵进行重建对比,验证了蒙特卡罗模拟与解析模型相结合方法对图像分辨率的改善效果。进一步比较了不同点源排列的重建效果,获得了优化的点源排布方案。相对于基于实验方法测量系统传输矩阵,本方法能以更合理的代价实现系统传输矩阵的精确建模,并能有效提高系统空间分辨率。     

外延硅dE／dX探测器的研制

本文介绍了厚度为５．２－６．０、１０－１３、１９μｍ，有效面积为２８－１５４ｍｍ＾２的外延硅ｄＥ／ｄＸ探测器的研制工艺，主要用途，测试结果（对９．８７ＭｅＶ α粒子的能损△Ｅ的分辨率为５６－１２８ｋｅＶ）和在核物理实验中的应用。     

多单元硅锂探测器

多单元硅锂探测器[Si(Li)]是同步辐射X射线的数字减影心血管成象技术中的关键光电敏感元件。 已制备具有30个分立单元,长40mm,宽15mm,厚5mm的预研用Si(Li)探测器,单元灵敏面积为0.9mm宽,单元间隙为0.1mm。在500V工作偏压下,单元平均漏电流为10—45nA,单元间电阻为10—20MΩ。因而,探测器不仅可以用于电流模式的成象系统,也可以用于脉冲模式的能谱应用。在室温下,从一个单元已得到的对59.6kev的γ射线的能量分辨率(FWHM)约10keV。     

NTD硅探测器

采用国产NTD硅单晶,研制了性能较好的NTD硅探测器。用它精确测定14MeV中子能量和作为γ射线计数器均取得了较满意的结果。其性能指标为:反向偏压1kV,漏电流≤5μA,26℃;对~(241)Am α源,FwHM为31-50KeV,26℃;对~(137)Cs 625 keV的内转换电子,FwHM为6.85LeV,-2℃。     

Detection of Low Energy Heavy Particles with Silicon Barrier Detectors

The performance characteristics of silicon surface barrier detectors have been investigated for detecting H+, He+, N+, Ne+ and Ar+ in the energy interval 6-100 keV. For a cryogenically cooled, 50 mm2, 1325? depletion depth detector the resolution for protons was 1.65 keV (FWHM). The resolution decreased as the particle mass increased being 6.5 keV for 40 keV Ar+. All particles exhibit pulse height linearity throughout the energy range.     

硅漂移探测器的制作工艺及特性研究

采用双面并行的平面工艺研制出了有源区面积5mm2的硅漂移探测器(SDD).这种双面并行的平面工艺使得SDD绝大部分正面和背面的pn结结构能够并行完成,极大地减少了工艺步骤,降低了器件制作的难度.对研制的SDD的漏电流、电势分布、光电子的漂移特性等进行了测量和分析,对233Pu a射线源的能谱进行了测量.对正常工作状态下出现的悬空阳极电位进行了分析和讨论.报道了利用阳极漏电流、光电子漂移特性、悬空阳极电位对SDD芯片进行中测和封装前快速筛选的方法.     

Silicon Detectors for Low Energy Particle Detection

Silicon detectors with very thin entrance contacts have been fabricated for use in the IMPACT SupraThermal Electron (STE) instrument on the STEREO mission and for the Solid State Telescopes on the THEMIS mission. The silicon diode detectors were fabricated using a 200 Aring thick phosphorous doped polysilicon layer that formed the thin entrance window. A 200 Aring thick aluminum layer was deposited on top of the polysilicon in order to reduce their response to stray light. Energy loss in the entrance contact was about 350 eV for electrons and about 2.3 keV for protons. The highest detector yield was obtained using a process in which the thick polysilicon gettering layer was removed by chemical etching rather than chemical mechanical polishing.     

基于3层硅探测器的主动式中子个人剂量计研制

研制了一种具有能量分辨能力的中子个人剂量计。该个人剂量计由3层硅探测器组成,硅探测器周围装有⁶LiF、聚乙烯和含硼聚乙烯作为转化体、慢化体和吸收体。个人剂量计有直读和解谱两种工作模式。直读模式将中子能区划分为低能、中能和快中子3个能区,可实时测量。解谱模式可获得快中子能区的中子能量分布。利用GEANT4程序模拟了7 MeV γ射线的能量沉积谱,设置适当的甄别域以降低γ射线的影响。采用GEANT4程序模拟了个人剂量计对不同能量入射中子的个人剂量当量率响应。在加速器单能中子参考辐射场中完成了单能中子剂量响应的实验校准,对模拟计算的响应函数进行了实验修正,并得出了不同能区的平均中子个人剂量当量率响应。     

碳化硅热中子探测器的优化设计

采用MC法对用于热中子探测的碳化硅探测器开展设计。优化了中子转换层参数和半导体器件参数,研究表明采用~(10)B作为中子转换材料,其最优厚度为2μm,在系统甄别阈为300 keV时对应的探测效率理论值为3.29%。制备了碳化硅外延层厚度20μm,灵敏区面积5 mm×5 mm的碳化硅器件,在外加反向偏压达180V时,其漏电流仅20.8 nA。性能测试表明:该器件对4.7-6.0 MeV的α粒子具有极好的能量线性,其线性度达0.999 97。对5.49 MeV的α粒子的能量分辨率为1.03%,对应半高宽57.3keV,与SiC高分辨α探测器分辨率相当。     

Thin Epitaxial Silicon for De/Dx Detectors

The techniques for fabricating thin self-supporting epitaxial films for dE/dx detectors have been studied. Detectors having thicknesses between 1 and 4 ?m with areas of 12.5 mm2 have been fabricated and tested. The response of the detectors has been studied with alpha particles, oxygen ions, and fission fragments.     

A TDC-Based System for X-Ray Imaging Detectors

An image acquisition system is presented for use with position sensitive detectors (PSD). The system is based on a high-resolution time-to-digital converter (TDC) and a field programmable gate array (FPGA). The detectors use gas as absorbing medium and two delay lines to identify the coordinates of each detected particle. The TDC translates the time information coming from the delay lines into digital words, from which the particle position coordinates are encoded. The FPGA is responsible for processing each event, controlling the data acquisition and communicating with a personal computer. 256 pixels$times$256 pixels images are stored into an on-board memory. This resolution is increased to 512 pixels$times$512 pixels by using a time multiplexing technique. The maximum data acquisition rate is 1.2 million events per second. X-ray images obtained with the system are shown, which illustrate the overall performance.     

Epitaxial Silicon Semiconductor Detectors Past Developments, Future Prospects

A review of the main physical characteristics of epitaxial silicon as it relates to detector development is presented. As examples of applications results are presented on (1) epitaxial silicon avalanche diodes (ESAD); signal-to-noise, non-linear aspects of the avalanche gain mechanism, gain-bandwidth product, (2) ultrathin epitaxial silicon surface barrier (ESSB) detectors, response to heavy ions, (3) an all-epitaxial silicon diode (ESD), response to heavy ions, charge transport and charge defect. Future prospects of epitaxial silicon as it relates to new detector designs are summarized.     

束流漂移对硅条探测器阵列测量的影响

为研究束流漂移对结构紧凑、覆盖立体角较大的硅条探测器阵列测量的影响,利用蒙特卡罗方法,模拟了不同方向、不同大小的束流漂移对熔合蒸发残余核α衰变和卢瑟福散射角分布的影响,表明束流漂移距离小于3.0 mm时,探测器阵列的对称性能将计数误差控制在10%以下。开展了25 MeV和40 MeV ⁶Li+²⁰⁹Bi体系的实验测量,利用监视器数据研究了束流漂移的情况,结果表明,所有轮次的束流漂移均未超过3.0 mm。对束流漂移进行修正后,用3种不同的立体角刻度方法得到了弹性散射角分布,感兴趣的40 MeV数据与文献数据基本一致。     

Analysis and Characterization of Pre-Diffusion in Multi-Linear Silicon Drift Detectors

Multi-linear silicon drift detectors (MLSDD) are silicon detectors in which signal electrons are confined within parallel drifting columns at few micrometers from the anodes' surface and transported towards point-like anodes by an electrostatic field. During the initial motion across the thickness the signal electrons spread in all directions to a given width - we call this phenomenon pre-diffusion - until the signal electrons are focused in the drift channels which suppress any further spread into adjacent channels. This work is devoted to the study of the initial motion of the electron cloud when the electrons are being focused toward the minimum of the potential energy. We developed an analytical model to predict the initial charge spread and carried out a detailed measurement campaign to evaluate the impact of the detector operating conditions and of the charge injection level on the initial charge spread. The design of the electron spread during pre-diffusion allows optimization of MLSDD for different applications.     

Low Temperature Characteristics of Ion Implanted Silicon Position Sensitive Detectors

The operation of ion implanted silicon position sensitive detectors at low temperatures will be described. The improved noise performance of the detector at these temperatures in both the energy and position modes will be analyzed and its implications on low energy applications will be discussed. A large part of the investigation was devoted to the study of boron implanted resistors and their noise properties both at room temperature and cryogenic temperatures.     

双面硅条探测器的研制与测试

研制了双面硅条探测器。探测器灵敏面积为48mm×48mm,厚约300μm,结面和欧姆面的硅条互相垂直,均由相互平行、宽度相等的48条组成,每条宽0.9mm、间距0.1mm。对其电气特性(耗尽偏压、反向漏电流、条间电阻)和探测特性(上升时间、能量分辨、条间串扰)进行了测试。在偏压为-15V时,各条平均反向漏电流小于10nA。对于从结面入射的5.157 MeV的α粒子,前放信号上升时间约45ns,结面各条的能量分辨率约0.6%~0.7%,基本无条间串扰;欧姆面各条能量分辨率较差,存在条间串扰。