An ultra-low background alpha detection system with a Micromegas-based time projection chamber

Area of Science:

• Nuclear Physics
• Particle Detection
• Radiation Detection

Background:

• Alpha radiation detection requires systems with ultra-low background noise for accurate measurements.
• Micro-pattern gaseous detectors, such as Micromegas, offer potential for sensitive particle detection.
• Traditional methods often face challenges in achieving sufficient background suppression for alpha identification.

Purpose of the Study:

• To present a time projection chamber (TPC) system for ultra-low background alpha radiation detection.
• To demonstrate the capability of a Micromegas-based TPC for alpha identification using multi-dimensional information.
• To evaluate the background count rate and alpha particle acceptance rate of the developed TPC system.

Main Methods:

• Development of a prototype TPC (15 × 15 × 6.5 cm³) filled with a neon and isobutene gas mixture.
• Utilized a low-noise, high-integration electronic system with multi-channel waveform sampling for signal readout.
• Employed a feature selection method to optimize background event suppression while retaining alpha particle signals.

Main Results:

• Achieved an ultra-low background count rate below 1.6 × 10⁻³ counts per minute (95% confidence level) within a 5 × 5 cm² effective area.
• Demonstrated a high acceptance rate of approximately 96% for 5.5 MeV alpha particles from an 241Am source.
• Successfully conducted tests including a 49-hour background measurement and tests with weak radioactive samples.

Conclusions:

• The Micromegas-based TPC system is effective for ultra-low background alpha radiation detection and identification.
• The multi-dimensional information processing capabilities of the TPC enable significant background suppression.
• The developed system shows promising performance for applications requiring sensitive alpha particle detection.