IEEE Trans Med Imaging. 2015 Mar;34(3):707-15. doi: 10.1109/TMI.2014.2317314. Epub 2014 Apr 14.
High resistivity gallium arsenide is considered a suitable sensor material for spectroscopic X-ray imaging detectors. These sensors typically have thicknesses between a few hundred μm and 1 mm to ensure a high photon detection efficiency. However, for small pixel sizes down to several tens of μm, an effect called charge sharing reduces a detector's spectroscopic performance. The recently developed Medipix3RX readout chip overcomes this limitation by implementing a charge summing circuit, which allows the reconstruction of the full energy information of a photon interaction in a single pixel. In this work, we present the characterization of the first Medipix3RX detector assembly with a 500 μm thick high resistivity, chromium compensated gallium arsenide sensor. We analyze its properties and demonstrate the functionality of the charge summing mode by means of energy response functions recorded at a synchrotron. Furthermore, the imaging properties of the detector, in terms of its modulation transfer functions and signal-to-noise ratios, are investigated. After more than one decade of attempts to establish gallium arsenide as a sensor material for photon counting detectors, our results represent a breakthrough in obtaining detector-grade material. The sensor we introduce is therefore suitable for high resolution X-ray imaging applications.
高阻砷化镓被认为是光谱 X 射线成像探测器的合适传感器材料。这些传感器的厚度通常在几百微米到 1 毫米之间，以确保高光子探测效率。然而，对于几十微米以下的小像素尺寸，一种称为电荷共享的效应会降低探测器的光谱性能。最近开发的 Medipix3RX 读出芯片通过实施电荷求和电路克服了这一限制，该电路允许在单个像素中重建光子相互作用的全部能量信息。在这项工作中，我们介绍了第一个带有 500μm 厚高阻、铬补偿砷化镓传感器的 Medipix3RX 探测器组件的特性。我们分析了它的性质，并通过在同步加速器上记录的能量响应函数演示了电荷求和模式的功能。此外，还研究了探测器的成像特性，包括调制传递函数和信噪比。在尝试将砷化镓作为光子计数探测器的传感器材料建立十多年后，我们的结果代表了获得探测器级材料的突破。我们引入的传感器因此适用于高分辨率 X 射线成像应用。
