Development of a portable low-background <i>α</i>/<i>β</i> imaging system based on Micromegas and waveform digitizing electronics

Abstract A prototype Time Projection Chamber (TPC) detector with Micromegas anode plane was developed for high-sensitivity detection of alpha ( α ) and beta ( β ) particles. The system includes a Micromegas-based TPC, an anti-coincidence detector for cosmic-ray discrimination, and a 128-channel readout electronics comprising a Front-End Board (FEB) and a Data Processing Unit (DPU). Laboratory evaluations demonstrated low electronics noise and good linearity over a dynamic range of 130 fC. Tests with potassium chloride (KCl) powder, which naturally contains 40 K, demonstrated the system's capability to resolve radioactive material distributions. Separate efficiency tests, conducted with 241 Am for α particles and 90 Sr for β particles, achieved detection efficiencies of over 90% and 83%, respectively. Background levels were suppressed to approximately 0.004 cpm/cm 2 for α and 0.6 cpm/cm 2 for β particles within a 70 mm-diameter incident window. These results demonstrate the system's potential for precise measurements in low-radioactivity environments, paving the way for future advancements in detector performance and applications.