 Dual-phase xenon detector

A liquid target with a gaseous charge-readout layer. An interaction produces prompt particle scintillation, conventionally S1, and ionization electrons that drift to the liquid surface. Extracted electrons produce gas electroluminescence, conventionally S2. Timing and light-pattern information give three-dimensional position; the S2/S1 distribution helps distinguish electron recoils from nuclear recoils. It does not remove neutron-induced single recoils, and the discrimination requires calibration.