DUSEL R&D: Detection of impurities in cryogenic liquids with extreme sensitivity

University Of Maryland, College Park, College Park MD

Investigators

Abstract

Recent years have seen a proliferation of experiments based on the liquid noble gas detector technology. Noble gases are an attractive medium for particle detectors due to their low ionization potential, high scintillation efficiency, long electron lifetime and low cost. These detectors are currently employed to address a wide variety of fundamental physics questions, including neutrinoless double beta decay, neutrino oscillations, rare muon decays, dark matter searches and solar neutrinos. Many of these questions are central to the scientific mission of an underground lab and similar detectors have been proposed for the initial suite of experiments at DUSEL. Most liquid detectors to date are of relatively modest size, with target masses ranging from a few kilograms to a few hundred kilograms. However, next-generation experiments are poised to push the boundaries far beyond the current state of the art. For an experiment to succeed in this new regime, it will be necessary to purify the cryogenic liquids far beyond what current technologies have achieved. For existing TPC-style detectors, the concentration of electronegative impurities must be less than about 100 ppt oxygen equivalent to avoid attenuation of the charge signal as it drifts through the detector volume. Therefore, the next set of experiments will require impurity concentrations from one to ten ppt, or free electron lifetimes from tens to hundreds of milliseconds. This award will enable the group to develop a new method for detecting extremely low concentrations of impurities, with the potential to extend current sensitivities by several orders of magnitude. As part of the Broader Impacts of this work, this impurity detector would find wide application for many of the fundamental physics experiments which are likely to be hosted by DUSEL. In addition, this work will also have significantly broader impact by serving to further the education of graduate students.