RII Track-4: Liquid Xenon Time Projection Chamber R&D on the Large Xenon Test Stand at LLNL

University Of South Dakota Main Campus, Vermillion SD

Investigators

Abstract

Non-technical Description The only known neutral fundamental particles, that also have mass, are neutrinos. This makes them the only candidates to be their own antiparticle. If the neutrino is its own antiparticle, we could resolve some outstanding curiosities, not the least of which being: "Why is the Universe made up of matter and not roughly equal amounts of matter and antimatter?" This fellowship will initiate a long-term collaboration between the University of South Dakota (USD) and the Lawrence Livermore National Laboratory (LLNL) that will perform research and development of liquid xenon detector technologies for the next generation of rare decay searches. This fellowship will provide the PI and USD graduate students with the opportunity to experiment with state of the art detector technologies that could one day be deployed in South Dakota in a next-generation multi-tonne-scale liquid xenon dark matter or neutrinoless double-beta decay search. Observation of the latter is the only feasible way to determine that the neutrino is, in fact, its own antiparticle. Both USD and LLNL are members of the much broader nEXO Collaboration that is working towards a proposal to build such an experiment deep underground, such as in the Sanford Underground Research Facility in South Dakota. Technical Description Large, monolithic liquid xenon time-projection chambers have been demonstrated to be among the most powerful tools for low-background rare-event searches. In particular, the direct dark matter search community has embraced them as the leaders of the next generation program that is beginning to take shape. EXO-200 has also demonstrated the potential for such a detector to meet the next generation target for a tonne-scale neutrinoless double-beta decay search. The goal of this fellowship will be to initiate a long-term collaboration between the University of South Dakota (USD) and the Lawrence Livermore National Laboratory (LLNL). This collaboration will leverage the large xenon test facility at LLNL to perform R&D towards a (five) tonne scale liquid-xenon time-projection chamber to eventually search for the neutrinoless double-beta decay of Xe-136 with the nEXO experiment. The primary objective of the LLNL test facility, once we finish construction and commissioning, will be to qualify the electric field for the full diameter of nEXO. However, it can house many of the novel detector systems being prototyped for nEXO including novel charge readout tiles and custom silicon photomultipliers. The test facility will also be used to prototype external xenon handling systems. Immersing the PI in this R&D nexus for nEXO will ensure that the PI will have the expertise to contribute to the ongoing success of the nEXO experiment. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.