  The R&D mission of the Accelerator Neutrino Neutron Interaction Experiment
(ANNIE) is described in detail. ANNIE is: (1) an important measurement of
neutrino-nucleus interactions focusing specifically on neutron production, and
(2) an R&D effort focused on using new photodetector technology and chemical
additives to make advanced water-base neutrino detectors. The ANNIE experiment
consists of a small Water Cherenkov detector, instrumented with both
conventional photomultiplier tubes (PMTs) and Large Area Picosecond
Photodetectors (LAPPDs) deployed on the Booster Neutrino Beam (BNB) at
Fermilab. The experiment is designed to proceed in two stages: a
partially-instrumented test-beam run using only PMTs (Phase I) for the purpose
of measuring critical neutron backgrounds to the experiment; and a physics run
with a fully-instrumented detector (Phase II). This paper gives preliminary
results of the first phase and described the detector design upgrades necessary
for the next phase.
