用于空间天文的硅微条探测器原型样机研制

A prototype silicon strip detector for space astronomy

γ射线的天文观测是目前天文观测的前沿课题,通过观测高能γ射线的能谱和空间分布,可以研究宇宙中暗物质的分布及其物理特性。在众多γ射线探测器中,硅微条探测器具有很高的位置分辨率和能量分辨率,并且可以拼接组成大探测面,非常适合探测粒子的径迹和能量。为了解决硅微条探测器的关键技术,包括探测器微组装、前端读出电子学、数据采集电路,实验室自主研制了探测器样机并进行一系列测试。该样机的384个通道在0～180f C的输入动态范围内具有很好的线性(积分非线性小于5%),同时具有很低的噪声(等效输入噪声电荷小于0.16 fC)。样机的宇宙线能谱曲线可以清晰分辨出最小电离粒子的峰位约2.8 fC,并且可以用朗道卷积高斯函数精确拟合。

[Background] One of the most attractive subjects in the astronomical observation is the γ-ray detection in space astronomy. Recent research shows that the spectrum and distribution of the high-energy γ-ray can be utilized to explore the dark matter's distribution and physical characteristics. Several detectors can be utilized to detect high energy γ-ray, and one of the most suitable candidates is the silicon strip detector which possesses very high position and energy resolution. Silicon strip detector can be used to accurately detect the traversing particle's track and energy, and can be easily assembled together to form a large detecting plane.[Purpose] This study aims to explore key technologies of the silicon strip detector, including high-precision assembly techniques, front-end electronics design and data acquisition board design.[Methods] First of all, a test system with a low leakage current was built to inspect the silicon strip sensor. Then, an automatic wire-bonder was employed to connect the wires of sensors and front-end electronics. The automatic bond-tester was used to test wires' firmness. Finally, a readout scheme based on the characteristics of the sensor was design, and the printed circuit board (PCB) layout of the front-end electronics was optimized. In order to design the data acquisition board, the logics in the key component field programmable gate array (FPGA) and the automatic data acquisition software in the host computer were implemented.[Results] A prototype silicon strip detector has been fabricated and tested. All 384 channels show a good linearity in the range of 0~180 fC and the non-linearity is less than 5%. The prototype's input equivalent noise is less than 0.16 fC. The cosmic ray test result shows a clear peak of the minimum ionizing particle of 2.8 fC and the spectrum matches the convoluted Landau and Gaussian fitting function.[Conclusion] The well behaved prototype demonstrates the validity and feasibility of the key technologies, and these technologies can be applied to the practical silicon strip detector for space astronomy.