基于堆叠结构的同步辐射时间分辨APD探测器的关键技术研究

APD detector, composed by the APD sensor and readout circuit, has become the mainstream detector used in ultrafast time-resolved experiments with synchrotron radiation. To improve the performance of the existing APD detectors, this project makes a research on a kind of APD detector with stacked structure. The novel detector sequentially stacks several reach-through APD sensors together, and each sensor has a thin absorption layer. Meanwhile, these reach-through APD sensors have a SACM structure. The time resolution is determined by the thickness of each sensor, while the quantum efficiency is determined by the total absorption layer thickness of all sensors. Therefore, the stacked APD detector can achieve a sub-nanosecond time resolution and a high quantum efficiency at the same time. Moreover, a new multi-channel readout circuit chip is designed for the stacked APD detector. The readout chip can provide a better match with the APD sensors. The integration level of the whole detector is also increased by using readout circuit chip. In this project, some critical scientific problems, such as the design principles and fabrication technologies of reach-through APD sensor with SACM structure, the stacking and packaging techniques of multiple APD sensors, and the design method of high-speed, low-noise readout circuit chip, are extensively investigated. The sensor and readout circuit chip will be fabricated and integrated. Finally, an APD detector with sub-nanosecond time resolution, high quantum efficiency and high integration level will be provided to the users. The studies on this project can prompt the technology development of time-resolved detector for synchrotron radiation and promise to get proprietary intellectual property rights of time-resolved detector for China.

APD探测器由传感器和读出电路两部分构成，是同步辐射超快时间分辨实验的主流探测器。针对现有APD探测器的不足，本项目研究一种堆叠式APD探测器。该探测器将多个吸收层较薄的SACM结构Reach-through型APD传感器顺序堆叠在一起，时间分辨由单管传感器的吸收层厚度决定，而量子效率则由多个传感器吸收层的整体厚度决定，可在获得亚纳秒时间分辨的同时实现高量子效率。同时探测器采用读出电路芯片实现多路读出，以更好地匹配APD传感器，提高集成度。本项目深入研究SACM结构的Reach-through型单管APD传感器的设计原理及制作工艺，多元APD传感器的堆叠与封装，高速、低噪声读出电路芯片的设计方法等关键科学问题，完成传感器与读出电路芯片的制造及集成，提供亚纳秒时间分辨、高量子效率、高集成度的APD探测器。本项目的研究可促进同步辐射时间分辨探测器的深入发展，并获得自主知识产权的时间分辨探测器。

基于雪崩光电二极管（APD）的探测器具有高计数率、低暗计数、大动态范围的特点，同时又具有纳秒级或更快的时间分辨能力，是当前超快X射线时间分辨实验中最常用的探测器，进一步提高其时间分辨能力和量子效率已成为X射线探测器领域的研究热点。. 本项目采用电阻率为150Ω•cm的外延片为基底，制作了光敏区厚度约为33μm性能稳定的APD传感器。该传感器采用拉通型APD结构+偏置保护环的技术。器件阵列为2×2，像素大小为1mm×1mm。传感器的测试结果如下：增益（G）为20@80V，50@88V；结电容<16pF；工作电压VOP为50V-90V；击穿电压VBD>110V；暗电流<1nA。然后，采用高增益电流转电压前置放大器+基线恢复器+高速电压甄别器+LVDS输出的结构，设计了一款芯片的面积为2.4mm×1.1mm的8通道读出电路芯片。该芯片的电器特性表明：当输入电荷量大于100fC时，芯片输出脉冲前沿的内在时间分辨（RMS）小于34.4ps；当输入电荷量为30fC–100fC时，芯片输出脉冲前沿的内在时间分辨（RMS）小于98ps。芯片单通道的计数率>3.3×108/s。最后，基于研发的APD传感器与ASIC芯片构成了本项目的APD探测器，并在北京同步辐射装置（BSRF）1W2B线站上对其进行了测试。探测器在14.4keV能量下的时间分辨：RMS=150ps；FWHM=355ps。. 本项目所设计的APD探测器已成功在北京同步辐射装置（BSRF）上得到了应用，利用该探测器实现了加速器束团结构测试、同步辐射吸收谱实验等。我国正在北京怀柔建设第四代光源—高能同步辐射光源，本项目的研究成果为进一步研发新光源所需的APD探测器打下了坚实的基础，具有广阔的应用前景。

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