Demonstration of the Prototype BetaCage, an Ultra-sensitive Screener for Surface Contamination

Material screening for low-energy betas and alphas is necessary for rare-event-search experiments, such as dark matter and neutrinoless double-beta decay searches where surface radiocontamination is a significant background. The BetaCage, a gaseous neon time-projection chamber, has been proposed as a screener for emitters of low-energy betas and alphas to which existent screening facilities are insufficiently sensitive. We have constructed and characterized a prototype of the BetaCage to demonstrate the viability of constructing a time-projection chamber out of materials consistent with radio-purity. The prototype has demonstrated sufficient energy resolution and stability to indicate the success of our basic design. We report on the details of the detection characteristics of the prototype BetaCage.