High resolution gamma ray detection in a dual phase xenon time projection chamber

Dual phase Xenon Time Projection Chambers (XeTPCs) are being used by several experiments as a promising technique for direct detection of dark matter. We report on the design and performance of a small 3-D sensitive dual phase XeTPC. The position resolution is 2 mm in the center of detector, limited by the hole size of the mesh at the proportional scintillation region. An energy resolution of 1.6%(σ/E) for 662 keV gamma rays is achieved in the very center of the detector by combining the ionization and scintillation signals at a drift field of 0.5 kV/cm. This represents the best energy resolution achieved among liquid xenon detectors to date. The energy resolution is only slightly dependent on the drift field. Better than 2% energy resolution (σ/E) for 662 keV gamma rays was achieved for drift fields between 100 V/cm and 2 kV/cm. If such a high position and energy resolution can be achieved in a large volume detector, the dual phase XeTPC will have potential applications in surveys of neutrinoless double-beta decay and in gamma ray imaging.