Research on weak signal readout systems for neutrinoless double-beta decay experiments based on bolometers

Abstract

This paper develops a prototype signal readout system based on the physical mechanism and signal-to-noise ratio of the ultralow voltage signal characteristics of a bolometer. The preamplifier module is one of the key difficulties of the prototype: the internal resistance is as high as one hundred MΩ, the signal frequency band is susceptible to low-frequency noise, and the high energy resolution requires a high signal-to-noise ratio that is matching the input impedance to design a preamplifier with a good common-mode rejection ratio and low inherent noise. Therefore, the preamplifier circuit is designed with an instrument amplifier. At present, the energy resolution of the bolometer is 500 ~ 1000 nV (root mean square, rms) at the input of the signal readout system. According to the calculation, the theoretical value of the inherent noise at the input end is 394 nVrms, including a theoretical value for the equivalent input voltage noise of 166 nVrms, while the actual measurement value is less than 180 nVrms, which is basically consistent with the theoretical value. In addition, the signal gain (10,000) and frequency response of the prototype are experimentally verified. The experimental results show that the gain is 9400, and the frequency and waveform are not distorted within the allowable error range; all of these parameters meet the design requirement.