Design of the Directional Beta Source for the Eos Experiment*

Eos is a ton-scale technology demonstrator for hybrid neutrino detection with water-based liquid scintillator (WbLS) that harnesses the benefits of both Cherenkov and scintillation light. The directionality of Cherenkov light and high yield of scintillation light will improve sensitivity and background rejection for a broad range of neutrino measurements. Eos is the first data-driven demonstration of such hybrid detection, as well as a testbed for novel technologies. To show that the detector does harness the benefits of Cherenkov detection, it is important to demonstrate its directional reconstruction capabilities. To accomplish this, we have designed and built a directional beta source, which is currently being deployed in Eos. It consists of a small capsule containing 90Sr and 106Ru sources that create a collimated beam of electrons. The calibration source has self-triggering capabilities and produces several Hz of tagged events. In this talk, the design and expected performance of the directional beta source in Eos will be presented.