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, 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 spectral photon sorting works as expected. We then present measurements of two different LAB-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.