A gaseous time projection chamber with Micromegas readout for low-radioactive material screening

Purpose 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.
Methods A gaseous TPC with a Micromegas readout plane of approximately 20 \times 20 \hbox cm^2 is successfully constructed for surface alpha contamination measurements.
Results We have characterized the energy resolution, gain stability, and tracking capability with calibration sources.
Conclusion 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 ) \times 10^-6 Bq/ \hbox cm^2 , comparable to the leading commercial solutions.