Spectral photon sorting for large-scale Cherenkov and scintillation detectors

We describe here measurements with a new device, the ``dichroicon,'' a Winston-style light concentrator built out of dichroic reflectors, which could allow large-scale neutrino detectors to sort photons by wavelength with small overall light loss. Photon sorting would benefit large-scale water or ice Cherenkov detectors such as Hyper-Kamiokande or IceCube by providing a measure of dispersion, which, in turn, could allow improved position reconstruction and timing. For scintillator detectors like JUNO and upgrades to SNO+ or KamLAND-ZEN or to water-based liquid scintillator detectors like Theia, dichroicons would provide effective discrimination between Cherenkov and scintillation light, allowing them to operate as true hybrid detectors. We include measurements with a prototype dichroicon using first a Cherenkov source to show that spectral photon sorting works as expected. We then present measurements of two different linear-alkyl-benzene-based liquid scintillator sources and demonstrate discrimination between Cherenkov and scintillation light. On the benchtop, we can identify Cherenkov light with better than 90% purity while maintaining a high collection efficiency for the scintillation light. First results from simulations of a large-scale detector are also presented.