A two-phase argon avalanche detector operated in a single electron   counting mode
  The performance of a two-phase Ar avalanche detector in a single electron counting mode was studied, with regard to potential application in coherent neutrino-nucleus scattering and dark matter search experiments. The detector comprised of a 1 cm thick liquid Ar layer and a triple-GEM multiplier operated in the saturated vapour above the liquid phase. Successful operation of the detector in single electron counting mode, in the gain range from 6000 to 40000, has for the first time been demonstrated. 
A. Bondar, A. Buzulutskov, A. Grebenuk, D. Pavlyuchenko, R. Snopkov,   Y. Tikhonov, V.A. Kudryavtsev, P.K. Lightfoot, N.J.C....