Development of an in-situ calibration device of firn properties for Askaryan neutrino detectors

• Published in: Proceedings of 37th International Cosmic Ray Conference — PoS(ICRC2021)
• Main Authors: Beise, Jakob, Glaser, Christian
• Format: Conference Object
• Language: English
• Published: Uppsala universitet, Högenergifysik 2022
• Subjects: Subatomic Physics; Subatomär fysik; Accelerator Physics and Instrumentation; Acceleratorfysik och instrumentering; Ross Ice Shelf; Antarc*; Antarctica; Ice Shelf
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-518040; https://doi.org/10.22323/1.395.1069

High energy neutrinos (E > 1017 eV) are detected cost-efficiently via the Askaryan effect in ice, where a particle cascade induced by the neutrino interaction produces coherent radio emission that can be picked up by antennas installed below the surface. A good knowledge of the near surface ice (aka firn) properties is required to reconstruct the neutrino properties. In particular, a continuous monitoring of the snow accumulation (which changes the depth of the antennas) and the index-of-refraction profile are crucial for an accurate determination of the neutrino's direction and energy. We present an in-situ calibration system that extends the radio detector station with a radio emitter to continuously monitor the firn properties by measuring time differences of direct and reflected (off the surface) signals (D'n'R). We optimized the station layout in a simulation study and quantified the achievable precision. We present 14 months of data of the ARIANNA detector on the Ross Ice Shelf, Antarctica, where a prototype of this calibration system was successfully used to monitor the snow accumulation with unprecedented precision of 1 mm. We explore and test several algorithms to extract the D'n'R time difference from noisy data (including deep learning). This constitutes an in-situ test of the neutrino vertex distance reconstruction using the D’n’R technique which is needed to determine the neutrino energy.