感应电荷交叉条形阳极光子成像探测器关键技术研究

Currently, photon-counting imaging detector with microchannel plate (MCP) and two-dimensional position-sensitive anode have important applications in many fields such as space ultraviolet astronomy, space remote sensing, deep space exploration, large aperture ground-based photoelectric imaging telescope and electro-optical countermeasures in China. However, now available detectors can’t satisfy requirements for both high spatial resolution and high count rate in some applications, which have become a choke point to block the further application of such detectors. Therefore, we introduce a kind of new photon-counting imaging detector based on an induced-charge cross strip anode which can achieve both high space resolution and high total count rate, meanwhile, solve some difficult problems on the image nonlinearity which come from the redistribution of charge by secondary electron emission from the surface of the anode into the gap between the anode and MCP stack. We will succeed in developing an open photon-counting imaging detector principle prototype with cross strip anode after overcoming some key technical problems such as the fabrication of induced charge cross strip anode, the development of position readouts with high signal-to-noise ratio (SNR) and position decoding algorithm, so far there are no published reports on this kind of detector internationally. This will be a basic research work for such detectors which can be used in UV, visible light and near-infrared space science in the near future.

目前，使用微通道板（MCP）和二维位置灵敏阳极的光子计数成像探测器在我国空间紫外天文学、空间遥感、深空探测、地基大口径光电成像望远镜、光电对抗等领域均有重要的应用背景，而国内现有的探测器无法满足一些兼具高空间分辨率及高计数率的应用需求，这已成为制约此类探测器进一步应用的瓶颈。为此本项目提出了一种具有感应电荷交叉条形阳极的光子计数成像探测器，它既能同时实现高空间分辨及高计数率，又能避免MCP出射的电子云在金属阳极上产生的次级电子所导致的图像非线性及不稳定性。拟通过解决高性能感应电荷交叉条形阳极制作、高信噪比位置读出电路的研制、位置解码算法等关键技术，研制开口式感应电荷交叉条形阳极光子计数成像探测器原理样机，为其未来在紫外、可见光及近红外波段的空间科学应用开展基础性研究工作。

完成了感应电荷XS阳极的光子计数成像探测器的研制工作，该探测器包括MCP堆、感应电荷XS阳极、位置读出电路及相应的图像实时采集和处理软件等几部分。每片MCP的直径25mm、有效口径18mm、长径比60：1、通道直径10um，两片MCP构成V型结构。电阻阳极位于XS阳极上部，其方块电阻为10兆欧姆~50兆欧姆，XS阳极有效面积20mmX20mm。首先，完成了XS阳极解码算法的模拟仿真工作，分析了XS阳极解码误差产生的原因及变化规律，得到了微通道板出射电子云的直径需要覆盖XS阳极约1.64个周期的最佳工作条件。其次，完成电阻阳极短脉冲感应电荷产生和传递机理研究工作，从理论上研究了来自MCP堆的电子云在电阻阳极上产生的感应电荷空间分布与电阻阳极的基片厚度、方块电阻间的关系。在此基础上完成了感应电荷XS阳极的设计与制备，所设计XS阳极采用四层结构，从上至下依次为上层条形电极、绝缘介质层、下层条形电极、绝缘基片共计四层。去掉了传统XS阳极的上层条形电极的地平面及其下面的绝缘介质，制备方法更简单。利用低温共烧陶瓷技术制备出上下层各有32个条形、阳极周期为0.635mm、上层条形宽度0.25mm、下层条形线宽0.385mm、有效面积为约20mmX20mm的XS阳极。再次，完成了位置读出电路的研制工作，位置读出电路包括低噪声前置放大整形芯片、高速多通道A/D转换芯片、FPGA控制电路及高速接口电路等几个部分。使用该位置读出电路对探测器的空间分辨率及最高计数率进行了检测，检测结果表明：各项技术指标均满足要求。