First results of a large-area cryogenic gaseous photomultiplier coupled to a dual-phase liquid xenon TPC

Abstract

We discuss recent advances in the development of cryogenic gaseous photomultipliers (GPM), for possible use in dark matter and other rare-event searches using noble-liquid targets. We present results from a 10 cm diameter GPM coupled to a dual-phase liquid xenon (LXe) TPC, demonstrating − for the first time − the feasibility of recording both primary ("S1") and secondary ("S2") scintillation signals. The detector comprised a triple Thick Gas Electron Multiplier (THGEM) structure with cesium iodide photocathode on the first element; it was shown to operate stably at 180 K with gains above 10 5 , providing high single-photon detection efficiency even in the presence of large alpha particle-induced S2 signals comprising thousands of photoelectrons. S1 scintillation signals were recorded with a time resolution of 1.2 ns (RMS). The energy resolution (σ/E) for S2 electroluminescence of 5.5 MeV alpha particles was ~9%, which is comparable to that obtained in the XENON100 TPC with PMTs. The results are discussed within the context of potential GPM deployment in future multi-ton noble-liquid detectors.

DARWIN: towards the ultimate dark matter detector

“…Stable operation of a 4" triple-THGEM GPM with a reflective CsI photocathode, coupled to a dual-phase LXe TPC, was recently demonstrated. It displayed a broad dynamic range, namely the capability to detect both single photons and massive α-induced S2 signals under the same conditions [135]. The feasibility of the 4π concept and the GPM PDE optimisation are subject to ongoing studies.…”

On the possibility of positive-ion detection in gaseous TPCs and its potential use for neutrinoless double beta decay searches in 136Xe

“…This will require a ~10 cm gap between the anode EL structure and its photon-detector array (which should be further screened by a grounded mesh). The photon detectors of the anode plane should probably not be SiPMs, to simplify the detection of the t0 signal above the dark count noise; instead, one can consider a closely packed array of photomultiplier tubes (PMTs) or an array of large, highly-pixelated, gaseous photomultipliers (GPMs) behind fused silica windows [60,61]. Both options will provide a very low dark count rate (DCR).…”

First results of Resistive-Plate Well (RPWELL) detector operation at 163 K

“…One example is their incorporation as a last amplification stage in a cryogenic gaseous photomultiplier (GPM), e.g. with a CsI photocathode [34,35], to detect and localize primary scintillation and/or electroluminescence photons. GPMs offer high spatial resolution (unlike conventional PMTs) and by far lower dark current compared to silicon photomultipliers (SiPMs) -a vital requirement in detectors searching for rare, low-energy signals, such as in darkmatter experiments.…”