单晶体多电极读出高纯锗探测器^(76)Ge的0νββ甄别研究  

0νββ discrimination of single-crystal multielectrode readout of high purity germanium detector^(76)Ge

作　　者：杨璟喆 曾志[1,2] 程建平 田阳[1,2] 李玉兰 YANG JingZhe;ZENG Zhi;CHENG JianPing;TIAN Yang;&LI YuLan(Department of Engineering Physics,Tsinghua University,Beijing 100084,China;Key Laboratory of Particle and Radiation Imaging,Ministry of Education,Beijing 100084,China;College of Nuclear Science and Technology,Beijing Normal University,Beijing 100875,China)

机构地区：[1]清华大学工程物理系,北京100084 [2]教育部粒子与辐射成像重点实验室,北京100084 [3]北京师范大学核科学与技术学院,北京100875

出　　处：《中国科学：物理学、力学、天文学》2023年第7期51-65,共15页Scientia Sinica Physica,Mechanica & Astronomica

基　　金：国家自然科学基金(编号:U1865205)资助项目。

摘　　要：^(76)Ge的无中微子双贝塔(0νββ)衰变探测实验中本底抑制十分关键,单电子(本底事例)和双电子(0νββ事例)事例甄别因其信号特征区分度极小而十分具有挑战性.本文针对单晶体多电极读出的高纯锗探测器建立了波形模拟研究方法,对双面交叉条型多电极高纯锗探测器的位置分辨能力进行了研究.同时通过搭建lightGBM模型,对多电极高纯锗探测器各个电极所收集的模拟波形进行分类训练.结果表明,该结构的多电极高纯锗探测器在电极分布方向具有良好的位置敏感特性,同时可以通过两端电极过中时间差确定粒子作用深度.基于所搭建的lightGBM模型对0νββ双电子事例的识别效果为68.4%.经验证,所训练lightGBM模型在保证0νββ信号事例没有被明显抑制的基础上,对本底中^(68)Ge和^(60)Co抑制效果相对显著,甄别前后分别可以被抑制3.33倍和2.66倍.结果表明,单晶体多电极读出的高纯锗探测器对于^(76)Ge的0νββ衰变探测的应用具备可行性,为将来在中国锦屏地下实验室对^(76)Ge的0νββ衰变实现event-by-event搜寻提供了重要参考.Experiments conducted to investigate the neutrinoless double-beta(0νββ)decay of^(76)Ge using a high purity germanium(HPGe)detector heavily rely on background suppression technologies to enhance their sensitivities.Differentiating between single-electron(background)and double-electron(0νββ)events is challenging because of the minimal discrimination between their respective signal characteristics.In this article,a waveform-simulation method is established for a single-crystal multielectrode HPGe detector,and the position resolution of the double-sided crossedstrip multielectrode HPGe detector is investigated.At the same time,the lightGBM model is built to classify and train the simulated waveforms collected by each electrode of the multielectrode HPGe detector.The results reveal that the multielectrode HPGe detector demonstrates good position sensitivity in the direction of electrode distribution.The depth of particle interaction can be determined by the time difference between waveforms collected by the electrodes.Based on the lightGBM model,the recognition effect of the 0νββdouble-electron events is 68.4%.The trained lightGBM model has been verified to exhibit a remarkable inhibitory effect on^(68)Ge and^(60)Co in the background.This can be attributed to the fact that the 0νββsignal event is not substantially inhibited and can therefore be inhibited by 3.33 and 2.66 times before and after the discrimination,respectively.The results show that the multielectrode HPGe detector can be feasibly applied to the 0νββdecay detection of^(76)Ge,which provides a reference for future event-by-event research on the 0νββdecay of^(76)Ge in the China Jinping Underground Laboratory.

关 键 词：无中微子双贝塔衰变 多电极高纯锗探测器 波形甄别方法 机器学习 

分 类 号：TL814[核科学技术—核技术及应用]