Feasibility study of a novel high-speed photon-counting X-ray imaging camera with enhanced sensitivity and spatial resolution

许多X射线成像探测器，从医学诊断到原子能级的检查，都基于与数码相机相同的技术。大多数X射线直接穿过这些电荷耦合器件(CCDs)和CMOS型探测器，因此有必要使用更厚的探测器(例如，CMOS型混合探测器)或闪烁体。然而，目前的方法产生的探测器系统的性能有限：CMOS混合技术需要复杂的特征限制最小像素尺寸和空间分辨率，而基于CCD的系统的读出速度受到较高噪声水平的限制。近年来，我们完成了一项由STFC资助的新型光子计数探测器的概念研究。电子倍增(EM)CCD是为夜间监视或夜视等微光成像而设计的。EM-ccd与标准ccd的不同之处在于增加了一个“增益寄存器”。通过将信号乘以数千，设备的有效读取噪声可以降低到亚电子级别，从而允许在非常高的速度下运行。如果将闪烁体耦合到EM-CCD，则这种低有效噪声可以分析单光子相互作用(光子计数)，提供更高分辨率的成像和能量识别。小面积(8 Mm X 8 Mm)闪烁体耦合的EM-CCD以2fps的速度工作，限制了潜在的应用。要将这项技术和专业知识转移到市场上，还需要进一步的开发。我们的目标是利用目前商业化的高速电子设备，生产大面积、高速的X射线探测器模块，该高速电子设备是由剑桥天文研究所由STFC资助的“幸运成像”开发的。通过将光纤锥形耦合到更大面积的EM-CCD，可以使面积增加44倍以上。据设想，一系列模块随后将形成一个阵列，创建一个更大的系统。我们还打算测试闪烁光纤(SFO)的适用性。虽然由于较低的光输出，SFO在很大程度上被忽略了，因为它与CCD一起使用，但它具有高度结构化的形式，最大限度地减少了信号传播。利用EM-CCD对信号施加增益的能力，有望产生高分辨率的积分系统。与以往的探测器相比，新模块的预期性能将提供更高的分辨率、更快的速度(增加光束线吞吐量)、通过更高的饱和前最大通量和更高的探测效率、更高的信噪比和更高的温度运行，从而获得更大的有效动态范围。该模块的预计规格将为用户提供这些实质性的好处，包括允许更高的光束线设施的吞吐量和无快门性能，提供低分辨率‘像素探测器’的高速和低速CCD系统的高分辨率。通过生产概念验证原型模块，这项技术不仅将向市场开放，而且EM-CCD的应用范围将显著扩大，为该设备打开新的市场。该探测器针对同步加速器设施的应用，如大分子结晶学、表面衍射或小角散射技术、高能X射线衍射和相衬成像。该探测器在全球的市场价值约为9400万美元，我们的目标是通过引入EM-CCD摄像系统，为生命科学中的荧光和发光标记领域带来相同的革命性性能增强。为了将这种技术和专业知识转移到市场上，我们建议在高性能成像传感器的领先设计者、开发商和制造商e2v Technologies的支持下建立一个概念验证模块。

Many X-ray imaging detectors, from medical diagnosis to the examination of energy levels in atoms, are based on the same technology as found in digital cameras. Most X-rays pass straight through these Charge Coupled Devices (CCDs) and CMOS detectors and it is therefore necessary to use a thicker detector (e.g. CMOS hybrid) or a scintillator. However, current methods produce detector systems with limited performance: CMOS-hybrid technology requires intricate features limiting the minimum pixel size and spatial resolution, whilst the readout speed of CCD-based systems is limited by higher noise levels.Over recent years we have completed an STFC funded concept study on a novel photon-counting detector. The Electron-Multiplying (EM) CCD was designed for low light level imaging such as night-time surveillance or night-vision. The EM-CCD differs from the standard CCD through the addition of a "gain register". By multiplying the signal by thousands, the effective read noise of the device can be reduced to the sub-electron level, allowing operation at very high speeds. If a scintillator is coupled to an EM-CCD then this low effective noise allows analysis of single photon interactions (photon counting), providing higher resolution imaging and energy discrimination.The small area (8mm x 8mm) scintillator-coupled EM-CCD operated at 2fps, limiting potential applications. Further developments are required to transfer this technology and expertise to the marketplace.We aim to produce a large area, high speed X-ray detector module, making use of the now commercially available high-speed electronics developed from the STFC funded 'Lucky Imaging' at the Institute of Astronomy, Cambridge. By coupling a fibre-optic taper to a larger area EM-CCD, an increase in area of over 44 times is possible. It is envisaged that a series of modules will then be formed into an array, creating a much larger system. We also aim to test the suitability of the scintillating fibre-optic (SFO). Whilst the SFO has largely been ignored for use with a CCD due to lower light output, it has a highly structured form, minimising the signal spread. With the EM-CCD's ability to apply gain to the signal, it is expected that a high-resolution integrating system may be produced.In comparison to previous detectors, the expected performance of the new module will give a higher resolution, faster speed (increasing beamline throughput), higher effective dynamic range through higher maximum flux before saturation and higher detection efficiency, higher signal to noise and operation at higher temperatures. The projected specifications of the module will provide these substantial benefits to users, including allowing higher throughput in the beamline facilities and shutter-less performance, providing the high speed of the low resolution 'pixel detectors' and the high resolution of the low speed CCD systems.Through the production of a proof of concept prototype module, not only will this technology be opened up to the marketplace, but the range of applications for the EM-CCD will be dramatically expanded, opening new markets for this device.This detector is aimed towards applications at synchrotron facilities such as macromolecular crystallography, surface diffraction or small-angle scattering techniques, high energy X-ray diffraction and phase-contrast imaging. Applications in medical imaging may also be envisaged for a larger array of modules.The market for this detector is approximately $94M worldwide and we aim to bring the same revolutionary performance enhancements that were experienced in the fields of fluorescent and luminescent markers in life sciences from the introduction of EM-CCD camera systems.To transfer this technology and expertise to the marketplace, we propose to build a proof of concept module with the support of e2v technologies, a leading designer, developer and manufacturer of high performance imaging sensors.