Development of a dual-phase xenon TPC with a quartz chamber for direct dark matter searches

The idea of a hermetic quartz chamber in a dual-phase xenon time projection chamber (TPC) has the potential to improve the detector sensitivity for direct dark matter searches in the future. A major challenge facing TPC detectors in future dark matter experiments will be the reduction of the internal background such as $^{222}$Rn and the deterioration of the ionization signal due to electronegative impurities. The hermetic quartz chamber can isolate the TPC’s sensitive volume from external interference and is thus expected to prevent contamination caused by radioactive and electronegative impurities, which originate from the outer detector materials. At the Kamioka Observatory in Japan, we have developed a TPC with a quartz chamber that contains a ⌀$ 48 \times 58$ mm volume of liquid xenon. At this development stage, we have not aimed for perfect hermeticity of the quartz chamber. Our aim here is twofold: first, to demonstrate via the use of a calibration source that the presence of quartz materials in the TPC does not impact its operation; and second, to perform quantitative measurements of the TPC’s characteristics. We successfully measured electron drift velocities of 1.2–1.7 mm/$\mu$s in liquid xenon under electric fields ranging from 75–384 V/cm, and also observed small S2 signals produced by a single ionized electron with a light yield of 16.5 $\pm$ 0.5 PE. These results were consistent with the expected values; therefore, our demonstrations provide a proof of principle for TPCs incorporating a quartz chamber.