WATCHMAN: demonstration of remote reactor monitoring with gadolinium doped water detectors

WATCHMAN (Water Cherenkov Monitor of AntiNeutrinos) is a US-based collaboration whose purpose is to demonstrate the feasibility of using a gadolinium-doped water Cherenkov detector to detect antineutrinos emitted by distant nuclear reactors. The relatively high rate of emission of antineutrinos from reactors leaves open the prospect of discovering, or excluding the existence of hidden reactors at up to hundreds of kilometer standoff. The goal of WATCHMAN is to demonstrate such detection by deploying a kiloton-scale water detector approximately 25 kilometers from an operating nuclear reactor, and measuring the antineutrino flux therefrom. Detection at this standoff may be useful in existing or future cooperative monitoring regimes. Moreover, a successful deployment will demonstrate and exercise the water-based technology on a large scale, and serve as a stepping-stone to the much larger 100 kiloton to Megaton —scale devices that would be required for true remote detection. Water-based technology is likely the only scalable approach to reaching such large detector sizes, and is also being considered for future large scale neutrino physics experiments. (author)