A Capillary Probe for Ion Extraction from Liquid Xenon

Double beta decay is a process whereby two neutrons simultaneously decay into protons, emitting two electrons. The 100 kg scale EXO-200 precisely measured these decays with the emission of two neutrinos (136Xe 2νββ), with a half-life to be 2.165±0.016(stat)±0.059(syst)×1021 years. If the neutrino is a Majorana fermion, double beta decays are also possible without the emission of any neutrinos. EXO-200 placed one of the most stringent lower limits on the 136Xe 0νββ decay half-life at 3.5×1025 years. Multi-ton detectors like the 5t nEXO are planned with ∼100 times greater reach. nEXO's projected half-life sensitivity is 1.35×1028 years. This is accomplished by stringent control of all sources of background, along with taking advantage of the rich energy and topological information and the exquisite self-shielding of a large time projection chamber (TPC) with scintillation light readout.Future upgraded detectors could also observe the 136Ba ions resulting from 136Xe double beta decays (so-named barium tagging) and eliminate all background signals other than the 2νββ decay. The high efficiency detection of a single ion following a double beta decay event in a potentially multi-ton detector medium is a challenging task. One proposed scheme is to extract 136Ba ions by flowing xenon through a small capillary for transport to subsequent stages of detection. Progress at Carleton University on the development of a capillary-based probe for individual ion extraction from liquid xenon will be presented, along with details of the experimental apparatus and the simulations of each step of the extraction.