First results of the two-phase argon avalanche detector performance with CsI photocathode

The performance of a two-phase Ar avalanche detector with CsI photocathode was studied, with regard to potential applications in coherent neutrino-nucleus scattering and dark matter search experiments. The detector comprised a 1 cm thick liquid Ar layer and a triple-GEM multiplier operated in the saturated vapour above the liquid phase; the CsI photocathode was deposited on the first GEM. Successful detection of both primary scintillation and ionization signals, produced by beta-particles in liquid Ar, has for the first time been demonstrated in the two-phase avalanche mode.