基于微通道板的电离室及其在同步辐射中的应用

在同步辐射装置中,气体电离室是定标光束线能量和评估能量分辨率的一个重要实验装置。为了摆脱电极探针式电离室的气体展宽对束线能量分辨率测定的限制,本文将微通道板(Microchannel Plate,MCP)应用于同步辐射光束线中的电离室,研制成功了具有高能量分辨率的电离吸收谱的探测系统。利用此系统测量标准气体在X射线入射时的电离吸收谱,通过分析测量所得谱线中吸收峰的展宽,可获得光束线的仪器展宽,本文以Ar的吸收谱为例给出了测量结果。     

软X射线光束线能量分辨率测量中 气体压强对谱线的影响研究

同步辐射软X射线光束线通常利用气体电离室来标定单色仪的能量及测量能量分辨率,通过分析拟合所得谱线的半高宽,可以对光束线的能量分辨能力进行定量评估.然而,传统的分析方法往往忽略了谱线中气体碰撞展宽的影响,从而导致所得能量分辨率略低于真实值.通过讨论气压对测量所得的谱线宽度的影响,提出了一种考虑气压修正的能量分辨率计算方法...     

软X射线条纹相机的静态性能标定

软X光扫描相机是对软X光时间特性进行研究的主要诊断工具。我们利用同步辐射作为光源,对它的静态性能：能量响应、增益等性能进行了相对标定,给出了软X光条纹相机的能量响应曲线和增益特性曲线,并与利用Henke的经验公式^[1]计算给出的响应曲线比较,其结果与理论较符合。     

微通道板的增益研究

微通道板(Microchannel Plate,MCP)是一种超快时间响应的电子倍增器件,可以直接用于带电粒子探测。利用这一特点研制了时间响应亚纳秒的基于反冲质子的MCP中子探测器,而MCP的增益对探测器的性能具有非常重要的作用,因此有必要对探测器中MCP的增益进行理论和实验研究。采用蒙特卡罗方法模拟计算了单个电子在单个微通道上进行倍增产生的二次电子数目,计算得到了单片MCP在不同电压下的电子增益,然后利用α粒子实验研究了两片MCP的增益。计算结果表明:单片MCP增益理论计算得到的结果与厂家测试给出的结果比较一致;实验结果表明:当每片MCP所加电压为800 V时,两片MCP的增益约为9.0×106。该方法简便易行,为研究MCP的增益提供了新的技术手段,并为研究基于MCP的中子探测器提供了理论基础。     

NSRL表面物理线站的性能测试及角分辨光电子能谱实验

介绍了中国科技大学国家同步辐射实验室（NSRL）表面物理站的调试及获得的初步结果。利用光电二极管进行了光束线光通量的测试,分别得到了3块光栅的光通量响应曲线。利用纯金样品的二次谐波和费米边分别对高能和低能部分的入射光子能量进行了标定,并给出了系统的能量分辨率。最后用同步辐射零级光和激光束对实验站的电子能量分析器进行准直,用Cu单晶样品的角分辨光电子能谱实验测试了整个系统的性能,结果表明,NSRL表面站能够满足用户开展角分辨光电子能谱实验的要求。     

γ射线探测器能量响应标定技术

叙述了γ射线探测器能量响应的标定原理和方法，即利用Compton散射将强⁶⁰Co源的1.25MeVγ射线转换为0.36~1.02MeV(25°~90°)范围内任意能量的系列单能γ射线；采用辐射屏蔽技术和提高能量分辨率方法对γ射线探测器进行了该能区的能量响应标定；通过MCNP程序对探测器的能量沉积趋势和不同散射角散射γ射线的能量分布进行模拟计算。结果表明：该标定系统信噪比达到了20∶1左右，能量分辨率约为6%，0.66MeV的灵敏度与标准¹³⁷Cs源直照标定的灵敏度基本一致。     

基于同步辐射光源的光电导探测器标定系统

将门控积分方法运用到光电导探测器的灵敏度标定中,发展了一套在北京同步辐射装置(BSRF)上对光电导探测器进行定时测量的方法,给出了利用这套标定系统在BSRF软X光站上对光电导探测器的测量结果。     

透射光栅在同步辐射光束线输出特性诊断中的应用

介绍了透射光栅在北京同步辐射装置3W1B光束线光源输出特性诊断中的应用,借助透射光栅进行了能量标定及分辨率的测量,并定性地给出了束线的高次谐波情况。     

闪烁纤维中子探测器灵敏度研究

用蒙特卡罗方法研究了1种闪烁纤维中子探测器对不同能量中子和伽玛射线的相对灵敏度，并在实验室对几个能点的灵敏度进行了标定。实验结果表明：理论计算与实验标定的探测器能量响应曲线趋势基本一致，探测器对2．5MeV中子和1．25MeV伽玛射线的灵敏度比值为5．3。利用实验数据对计算值进行校正，可给出探测器能量响应全曲线。     

北京同步辐射3B1束线软X射线光源及探测器灵敏度标定

本文简单介绍了北京同步辐射装置３Ｂ１束线软Ｘ测量装置的结构与概况，从单色器能量分辨，绝对光子能及出射光强线性三个方面对该装置光源特性进行了系统的研究，初步建立了标定用辐射场，并为用于惯性约束聚变的软Ｘ射线探测器进行了灵敏度标定，得到比较理想的结果。     

PET detector using waveshifting optical fibers and microchannelplate PMT with delay line readout

We are developing a positron emission tomography (PET) detector with depth of interaction (DOI) sensitivity for breast and small animal imaging. The detector uses layers of high density scintillators sandwiched between orthogonal ribbons of wavelength shifting optical fibers. The fibers are coupled to microchannel plate (MCP)-based position sensitive photomultiplier tubes (PSPMTs) containing a crossed delay line readout anode. Preliminary measurements have been made using blue-green waveshifting fiber ribbons coupled to Lu₂(SiO₄)O:Ce (LSO). The measured photoelectron yield due to wavelength shifted light from the fibers is sufficient to ensure a Poisson probability of only 1.0% that no photoelectron is generated in a given MCP PSPMT. Measurement of internally reflected scintillation light permits energy resolution of better than 25% at 511 keV. Optical fiber readout of high density inorganic crystals provides a significantly larger detective area per unit phototube area than do one-to-one coupling schemes using PSPMTs. With its ability to accurately image single photons, the MCP PSPMT solves problems that have prevented other types of PSPMTs from being used in such a configuration, namely poor resolution at the low light output level of the optical fibers     

应用ITO膜作电荷收集极的位置灵敏探测器

首次尝试将ITO（Indium Tin Oxide）膜与微通道板（Microchannel Plate）结合用作位置灵敏探测器，并对该探测器的线性、位置分辨及探测效率作了测试，得到了令人满意的结果。     

Ion guiding in alumina capillaries: MCP images of the transmitted ions

Transmission of a few keV impact energy Ne⁶⁺ ions through capillaries in anodic alumina membranes has been studied with different ion counting methods using an energy dispersive electrostatic spectrometer, a multichannel plate (MCP) array and sensitive current-measurement. In the present work, we focus our attention to the measurements with the MCP array. The alumina capillaries were prepared by electro-chemical oxidation of aluminium foils. For the present experiments guiding of 3-6 keV Ne⁶⁺ ions has been studied in two samples with capillary diameter of about 140 nm and 260 nm and with capillary length of about 15 μm. At these energies, the ions have been efficiently guided by the capillaries up to few degrees tilt angle. In this work, we compare the results obtained by the energy dispersive spectrometer to those studied by the MCP array.     

Neutron Collimation With Microchannel Plates: Calibration of Existing Technology and Near Future Possibilities

A new type of high performance and compact neutron collimator can be manufactured from Gd- or B-doped microchannel plates (MCPs). Structures only a few mm thick have very narrow rocking curves and high out-of-angle rejection ratios, as observed previously with a cold neutron beam. We present the results of measurements with a collimated (L/D ratio ~280:1) thermal neutron beam. MCP collimators doped with 3 mole % of ^natGd₂O₃ as well as doped with 10 mole % of ¹⁰B₂O₃ were calibrated for transmission versus tilt angle. The MCPs used in this study were only 0.6 and 0.8 mm thick with ~8.5 mum circular pores on 11.5 mum centers. All the measured rocking curves agree well with the theoretically predicted performance. Both experimental and modeling results indicate that very efficient MCP collimators (with <0.1deg wide rocking curves and a rejection ratio exceeding 10³) can be built with the existing technology. The possibility to manufacture collimators with very large L/D ratios exceeding 1000:1 is also discussed for the case of unetched MCPs. The peak transmission of such devices with very sharp rocking curves will be limited to ~40% by the transmission of the undoped glass. Application of MCP collimators for scatter rejection in neutron radiography is also considered in terms of possible image distortions, which are shown to occur only for the systems with detector spatial resolution better than 20 mum FWHM     

Investigation of a Multi-Anode Microchannel Plate PMT for Time-of-Flight PET

We report on an investigation of a mulit-anode microchannel plate PMT for time-of-flight PET detector modules. The primary advantages of an MCP lie in its excellent timing properties (fast rise time and low transit time spread), compact size, and reasonably large active area, thus making it a good candidate for TOF applications. In addition, the anode can be segmented into an array of collection electrodes with fine pitch to attain good position sensitivity. In this paper, we investigate using the Photonis Planacon MCP-PMT with a pore size of 10 μm to construct a PET detector module, specifically for time-of-flight applications. We measure the single electron response by exciting the Planacon with pulsed laser diode. We also measure the performance of the Planacon as a PET detector by coupling a 4 mm × 4 mm × 10 mm LSO crystal to individual pixel to study its gain uniformity, energy resolution, and timing resolution. The rise time of the Planacon is 440 ps with pulse duration of about 1 ns. A transit time spread of 120 ps FWHM is achieved. The gain is fairly uniform across the central region of the Planacon, but drops off by as much as a factor of 2.5 around the edges. The energy resolution is fairly uniform across the Planacon with an average value of 18.6±0.7% FWHM. While the average timing resolution of 252±7 ps FWHM is achieved in the central region of the Planacon, it degrades to 280±9 ps FWHM for edge pixels and 316±15 ps FWHM for corner pixels. We compare the results with measurements performed with a fast timing conventional PMT (Hamamatsu R-9800). We find that the R9800, which has significantly higher PDE, has a better timing resolution than the Planacon. Furthermore, we perform detector simulations to calculate the improvement that can be achieved with a higher PDE Planacon. The calculation shows that the Planacon can achieve significantly better timing resolution if it can attain the same PDE as the R-9800, while only a 30% improvement is needed to yield a similar timing resolution as the R-9800.     

惰性气体β-γ符合测量系统探测器能量及分辨率刻度

β-γ符合法是全面禁止核试验条约(CTBT)放射性核素核查中惰性气体氙测量的一种重要方法,探测器能量及分辨率刻度是其首要解决的关键技术。本工作详细介绍了β-γ符合测量系统NaI(Tl)闪烁体和塑料闪烁体探测器能量及分辨率刻度的方法和结果,采用γ放射性核素点源刻度NaI(Tl)γ射线能量及分辨率,利用137Cs661.66keVγ射线康普顿散射电子刻度塑料闪烁体β射线能量及分辨率,并与131Xem内转换电子刻度的β射线能量分辨率结果进行了比较。结果表明:用137Cs康普顿散射电子刻度塑料闪烁体β射线能量是一种简便可行的方法,但用其刻度的β射线分辨率比实际的大。     

基于超高分辨γ射线探测器的蒙特卡罗模拟

能量分辨率是γ射线探测器关键技术指标之一,直接关联γ射线全能峰的尖锐程度、分离程度,从而影响全能峰被识别、区分的能力。提高γ探测器的能量分辨率,是γ探测器发展的一个重要方向,近年发展起来的超高分辨γ射线探测器,能达到25 e V@103 ke V的能量分辨率,其相对目前能量分辨率最好的高纯锗探测器的能量分辨率高一个数量级,因此超高分辨超导γ射线探测器成为了一大研究热点。为了推动超高分辨率γ探测器关键技术的实验研究,利用MCNP5采用了不同能量的射线源、不同规格的吸收体以及不同的支撑环境对超高分辨超导γ射线探测器的探测结果进行了模拟。这些模拟对于探测器的模型优化以及谱仪的设计有重要的指导作用。     

适用于研究低能裂变碎片电荷分布的探测器装置

为研究²⁵²Cf自发裂变碎片电荷分布，建立了由屏栅电离室和ΔE-E粒子望远镜构成的探测器系统。在该系统中，将薄的屏栅电离室作为碎片的ΔE探测器，E探测器是金硅面垒半导体探测器。通过分析实验测量的4参数关联数据，得到了²⁵²Cf自发裂变碎片质量数、动能及碎片在气体ΔE探测器中的能量沉积分布等物理量。用多高斯（multi-Gaussian）分布函数对ΔE探测器的能量响应函数进行最小二乘法拟合，得到了在固定质量数A^*_L和动能条件下轻碎片的电荷分布。结果表明：该探测器系统的电荷分辨能力Z/ΔZ约为40∶1；建立起来的测量技术可用于测定²³⁵U(n,f)和²³⁹Pu(n,f)反应碎片的电荷分布。     

Evaluation of CdZnTe spectrometer performance in measuring energy spectra during interventional radiology procedure

Interventional radiology has been beneficial for patients for over 30 years of age with the combination of diagnostic and therapeutic methods. The radiation affecting occupationally exposed workers should be evaluated by means of the energy spectra and flux of X-rays in the treatment room. The present study aims to obtain the energy spectra of interventional procedures and study the capability of some detectors to evaluate the dose in interventional procedures. These measurements were taken by silicon-drift, Cd Te, and Cd Zn Te detectors. The energy spectra were corrected by the energy-response curve of each detector. The energy-response curves of silicon-drift and Cd Te detectors provided by the manufacturers specification were used. The energy response of the Cd Zn Te detector was measured by ~(133)Ba and ~(152)Eu c sources. The experimental data were compared with the simulation results, and their perfect agreement provides a way to correct the energy or dose response, which can be used for the personal dosimeter developed by our group.Moreover, the measured energy spectra can be used in individual radiation protection. The present study shows that the Cd Zn Te detector is a good candidate detector in interventional procedures.