In this study, we present a time projection chamber (TPC) system for low-background beta radiation measurements. The system consists of a TPC with a two-dimensional strip readout Micromegas and an anti-coincidence detector with readout pads for cosmic ray vetoing. The detector system uses an AGET-based waveform sampling system for data acquisition. The beta detection capability of the system was verified through an experimental test using 90Sr beta source. In addition, a dedicated simulation program based on Geant4 was developed to model the entire detection process, including the responses to both the beta source and background radiation. The simulation results were compared with the experimental data for both beta and background samples, and they were in good agreement. Simulation samples were used to optimize and train the classification models for beta and background discrimination. By applying the selected model into test data, the system achieved a background rate of <InlineEquation ID="IEq1"> <EquationSource Format="TEX">$0.49\,\text {cpm/cm}^{2}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>0.49</mn> <mspace width="0.166667em" /> <msup> <mtext>cpm/cm</mtext> <mn>2</mn> </msup> </mrow> </math></EquationSource> </InlineEquation> while retaining more than 55% of 90Sr beta signals within a 7 cm diameter detection region. Further analysis revealed that approximately 70% of the background originated from environmental gamma radiation, while the remaining contribution mainly originated from the intrinsic radioactivity of the detector materials, particularly the FR-4-based field cage and readout plane. Based on the knowledge gained from the experiments and simulations, an optimization of the TPC system was proposed, with the simulation predicting a potential reduction in the background rate to <InlineEquation ID="IEq2"> <EquationSource Format="TEX">$0.0012\,\text {cpm/cm}^{2}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>0.0012</mn> <mspace width="0.166667em" /> <msup> <mtext>cpm/cm</mtext> <mn>2</mn> </msup> </mrow> </math></EquationSource> </InlineEquation>.

A low-background beta detection system using a time projection chamber

期刊论文
发表日期：

2026年3月28日

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Rui-Yang Zhang,
Zhi-Yong Zhang,
Zeng-Xuan Huang,
Yong Zhou,
Jian-Bei Liu,
Song-Song Tang,
Yuan-Fei Cheng,
Chang-Qing Feng,
Ming Shao,
Yi Zhou

摘要

In this study, we present a time projection chamber (TPC) system for low-background beta radiation measurements. The system consists of a TPC with a two-dimensional strip readout Micromegas and an anti-coincidence detector with readout pads for cosmic ray vetoing. The detector system uses an AGET-based waveform sampling system for data acquisition. The beta detection capability of the system was verified through an experimental test using ⁹⁰Sr beta source. In addition, a dedicated simulation program based on Geant4 was developed to model the entire detection process, including the responses to both the beta source and background radiation. The simulation results were compared with the experimental data for both beta and background samples, and they were in good agreement. Simulation samples were used to optimize and train the classification models for beta and background discrimination. By applying the selected model into test data, the system achieved a background rate of $0.49\,\text {cpm/cm}^{2}$ $0.49 {cpm/cm}^{2}$ while retaining more than 55% of ⁹⁰Sr beta signals within a 7 cm diameter detection region. Further analysis revealed that approximately 70% of the background originated from environmental gamma radiation, while the remaining contribution mainly originated from the intrinsic radioactivity of the detector materials, particularly the FR-4-based field cage and readout plane. Based on the knowledge gained from the experiments and simulations, an optimization of the TPC system was proposed, with the simulation predicting a potential reduction in the background rate to $0.0012\,\text {cpm/cm}^{2}$ $0.0012 {cpm/cm}^{2}$ .