无中微子双贝塔衰变实验无气体电子雪崩TPC读出的电荷灵敏前置放大器降噪方法研究

华中师范大学针对无中微子双贝塔衰变实验研制了单电极无气体电子雪崩放大直接电荷收集传感器Topmetal-S，由其组成的电荷读出平面制成高压气体时间投影室（TPC）实现高能量分辨率，最大的挑战是极低噪声电荷灵敏前置放大器的设计。申请人前期研究，实现了其输入等效电荷噪声（ENC）约为30e-。为了进一步降低ENC，本项目旨在研究电荷灵敏前置放大器的降噪方法：1）提出一种新型结构的电荷灵敏前置放大器，能够保证电荷收集电极面积不变条件下减小探测器输入电容，并进行低噪声设计；2）研究极低带宽小面积的低通滤波器，减小偏置节点噪声和背景噪声；3）研究减小衬底噪声耦合效应技术与方法。通过以上降噪方法研究，能够设计出低噪声电荷灵敏前置放大器，实现其ENC<20e-的目标，与前期研究相比，ENC降低33%，并集成于下一代Topmetal-S中。本项目的研究对提高TPC的能量分辨率具有重要意义。

A direct-charge collecting sensor without gas-electron avalanche amplification called Topmetal-S for neutrinoless double-beta decay experiments has been developed by Central China Normal University. The Topmetal-S features a single charge collection electrode. A high-pressure gaseous Time Projection Chamber (TPC) made of a charge readout panel composed of Topmetal-S sensors can achieve high energy resolution. The immediate challenge is to develop a charge sensitive pre-amplifier with very low noise. In the previous researches, the input Equivalent Noise Charge (ENC) of the charge sensitive pre-amplifier is about 30 e-. In order to reduce the ENC furtherly, this project aims to research noise reduction methods. 1) A novel-structure low-noise charge sensitive pre-amplifier is proposed hence decreasing the input capacitance of the detector without reducing the size of the charge collection electrode. 2) A very low bandwidth and small area low-pass filter is studied to reduce the noise on each bias node and reject backgrounds. 3) The techniques and methods of the substrate noise coupling effect reduction are studied. Based on above noise reduction methods, we can design a novel charge sensitive pre-amplifier with an ENC of less than 20 e-, reducing the ENC by 33% compared to the previous one. The novel charge sensitive pre-amplifier will be installed in the next-generation Topmetal-S. The researches of this project are of great significance to improve the energy resolution of the TPC.