First results on FHM — a Floating Hole Multiplier

A proof of principle of a novel concept for event recording in dual-phase liquid xenon detectors — the Floating Hole Multiplier (FHM) — is presented. It is shown that a standard Thick Gaseous Electron Multiplier (THGEM), freely floating on the liquid xenon surface permits extraction of electrons from the liquid to the gas. Secondary scintillation induced by the extracted electrons in the THGEM holes as well as in the uniform field above it was observed. The first results with the FHM indicate that the concept of floating electrodes may offer new prospects for large-scale dual-phase detectors, for dark matter searches in particular.