A Precision Neutrino Flux Detector at the Spallation Neutron Source

For the COHERENT Collaboration. The first observation of coherent elastic neutrino-nucleus scattering (CEvNS) at the Spallation Neutron Source demonstrated the capability of the facility in experimental neutrino physics. The COHERENT collaboration is now measuring the nuclear target scaling of the interaction with multiple small-scale, first-light detectors. The potential of the neutrino source is fully realized with a suite of high precision neutrino measurements with ton-scale instruments. The neutrino flux is known within 10% and will present a floor in the uncertainty for detectors now being considered for a precision program. We present here a heavy water detector concept to directly measure the neutrino flux at the SNS using the well-known ν_e-deuteron charged current cross-section. This interaction, known to a few percent, is detected via Cherenkov light from the produced electron.  A sufficient number of interactions will be recorded to achieve this precision within a year in a ton-scale detector with an optimized design to suppress backgrounds.