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首页> 外文学位 >Gamma-ray imaging and polarization measurement using three-dimensional position-sensitive cadmium zinc telluride detectors.
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Gamma-ray imaging and polarization measurement using three-dimensional position-sensitive cadmium zinc telluride detectors.

机译：使用三维位置敏感的碲化​​镉锌锌探测器进行的伽马射线成像和偏振测量。

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摘要

The three-dimensional position-sensitive CdZnTe detector is a novel room temperature semiconductor gamma-ray spectrometer. It was initially developed to achieve good energy resolution even if the detector material is not uniform and has charge trapping problems. However, the capability of position sensing, as well as the excellent energy resolution, enables 3-D CdZnTe detector systems to perform gamma-ray Compton imaging and polarization measurements.; Among various reconstruction algorithms, a direct algorithm such as filtered back-projection is preferable if computational time is critical. A real-time filtered back-projection algorithm based on spherical fast Fourier transforms was developed for Compton imaging devices. It was the first time that real-time imaging was realized on similar Compton imaging devices.; A near field imaging technique was developed to image gamma-ray sources in the vicinity of the detector by taking advantage of the finite size of the detector. In this work, it was demonstrated by simulations that more powerful 3-D imaging capability can be achieved with detector arrays such as the Polaris system currently under development.; In conventional Compton camera systems, the image reconstruction is performed in 2-D or 3-D spatial coordinates for a specific gamma-ray energy. A new energy-imaging integrated deconvolution method using the MLEM algorithm was developed to reconstruct he source distribution in a combined spatial and energy space. It was the first time that the spectral deconvolution method was applied in the spatial and spectral domain simultaneously. By employing this energy-imaging integrated deconvolution algorithm, a Compton camera can provide the image at any specific energy, as well as the spectrum at any specific direction. Since the ML solution estimates the true incident gamma-ray intensity, the deconvolved energy spectrum at the source direction is free of Compton continua. To overcome the difficulty of pre-storing the huge system response function in the memory, an analytical model was developed so that the system response function can be calculated event by event.; A 3-D position-sensitive CdZnTe detector can also perform gamma-ray polarization measurements. When a polarized gamma-ray photon undergoes a Compton scatter, the probability for the photon to scatter at a fixed scattering angle depends on the azimuthal angle. The polarization of incident gamma rays can be measured using this effect by observing the angular distribution of scatters. We successfully demonstrated that a single 3-D position-sensitive CdZnTe detector can be an effective instrument to detect the polarization of incident gamma rays.
机译：三维位置敏感的CdZnTe检测器是一种新型的室温半导体伽马射线光谱仪。最初开发该技术是为了获得良好的能量分辨率，即使检测器材料不均匀且存在电荷捕获问题。然而，位置感应的能力以及出色的能量分辨率使3-D CdZnTe检测器系统能够执行伽马射线康普顿成像和偏振测量。在各种重建算法中，如果计算时间很关键，则最好使用直接算法，例如滤波反投影。针对康普顿成像设备，开发了一种基于球面快速傅立叶变换的实时滤波反投影算法。这是第一次在类似的康普顿成像设备上实现实时成像。通过利用探测器的有限尺寸，开发了近场成像技术以对探测器附近的伽马射线源成像。在这项工作中，通过仿真证明，利用探测器阵列（例如当前正在开发的Polaris系统）可以实现更强大的3-D成像功能。在常规的康普顿相机系统中，对于特定的伽马射线能量，在2D或3D空间坐标中执行图像重建。开发了一种使用MLEM算法的新的能量成像集成反卷积方法，以重建空间和能量空间组合中的源分布。这是光谱去卷积方法首次在空间和光谱领域同时应用。通过采用这种能量成像集成的去卷积算法，康普顿相机可以提供任何特定能量的图像以及任何特定方向的光谱。由于ML解决方案估计了真实的入射伽马射线强度，因此在源方向上解卷积的能谱没有康普顿连续性。为了克服将巨大的系统响应函数预先存储在内存中的困难，开发了一种解析模型，以便可以逐个事件地计算系统响应函数。 3-D位置敏感的CdZnTe检测器还可以执行伽马射线偏振测量。当偏振伽马射线光子经历康普顿散射时，光子以固定散射角散射的概率取决于方位角。可以通过观察散射的角度分布，使用这种效果来测量入射伽马射线的偏振。我们成功地证明了单个3-D位置敏感CdZnTe检测器可以是检测入射伽马射线偏振的有效仪器。

著录项

  • 作者

    Xu, Dan.;

  • 作者单位

    University of Michigan.;

  • 授予单位 University of Michigan.;
  • 学科 Engineering Nuclear.
  • 学位 Ph.D.
  • 年度 2006
  • 页码 169 p.
  • 总页数 169
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 原子能技术;
  • 关键词

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