BetaCage: an Ultra-sensitive Screener for Surface Contamination

Commercial radioactivity counting techniques for alpha and beta particles are unable to meet the stringent screening requirements for next-generation low-background rare-event search experiments because of inadequate sensitivity. To meet this need, we are developing a new screener, BetaCage, a gaseous neon time-projection chamber. Using radiopure materials for construction, active and passive shielding from extrinsic backgrounds, large counting area and minimal detector mass, BetaCage will be able to achieve sensitivities of $10^{-5}$counts keV$^{-1}$kg$^{-1}$day$^{-1}$ in a few days of running time. We present the status of a prototype we are currently building and testing, to inform the design and construction of the final version.