An aerogel Cherenkov detector for multi-GeV photon detection with low   sensitivity to neutrons
  We describe a novel photon detector which operates under an intense flux of neutrons. It is composed of lead-aerogel sandwich counter modules. Its salient features are high photon detection efficiency and blindness to neutrons. As a result of Monte Carlo (MC) simulations, the efficiency for photons with the energy larger than 1 GeV is expected to be higher than 99.5% and that for 2 GeV/$c$ neutrons less than 1%. The performance on the photon detection under such a large flux of neutrons was measured for a part of the detector. It was confirmed that the efficiency to photons with the energy $>$1 GeV was consistent with the MC expectation within 8.2% uncertainty. 
Y. Maeda, N. Kawasaki, T. Masuda, H. Morii, D. Naito, Y. Nakajima, H.   Nanjo, T. Nomura, N. Sasao, S. Seki, K. Shiomi, T. S...
physics.ins-det hep-ex