A Gaseous Time Projection Chamber with Micromegas Readout for Low Radioactive Material Screening

TL;DR

This paper presents a gaseous TPC with Micromegas readout designed for low radioactive material screening, demonstrating its effectiveness in measuring alpha contamination with competitive background suppression.

Contribution

The study introduces a novel gaseous TPC with Micromegas readout for low-background screening, including characterization and background suppression techniques.

Findings

Achieved an alpha background rate of 0.13±0.03 μBq/cm²

Demonstrated stable energy resolution and gain

Confirmed tracking capability for contamination measurements

Abstract

Low radioactive material screening is becoming essential for rare event search experiments, such as neutrinoless double beta decay and dark matter searches in underground laboratories. A gaseous time projection chamber (TPC) can be used for such purposes with large active areas and high efficiency. A gaseous TPC with a Micromegas readout plane of approximately 20$\times$20 cm$^2$ is successfully constructed for surface alpha contamination measurements. We have characterized the energy resolution, gain stability, and tracking capability with calibration sources. With the unique track-related background suppression cuts of the gaseous TPC, we have established that the alpha background rate of the TPC is 0.13$\pm$0.03 $\mu$Bq/cm$^2$, comparable to the leading commercial solutions.