Measurement of sound speed vs. depth in South Pole ice for neutrino astronomy

• Published in: Astroparticle Physics
• Main Authors: Abbasi, R., Abdou, Y., Ackermann, Markus, Adams, J., Aguilar, J. A., Ahlers, M., Andeen, K., Auffenberg, J., Bai, X., Baker, Mark D., Barwick, S. W., Bay, R., Bazo Alba, J. L., Beattie, K., Beatty, J. J., Bechet, S., Becker, J. K., Becker, K.-H., Benabderrahmane, M. L., Berdermann, J., Berghaus, P., Berley, D., Bernardini, E., Bertrand, D., Besson, D. Z., Bissok, M., Blaufuss, E., Boersma, D. J., Bohm, C., Bolmont, J., Böser, S., Botner, O., Bradley, L., Braun, J., Breder, D., Castermans, T., Chirkin, D., Christy, B., Clem, J., Cohen, S., Cowen, D. F., d'Agostino, M. V., Danninger, M., Day, C. T., de Clercq, C., Demirörs, L., Depaepe, O., Descamps, F., Desiati, P., de Vries-Uiterweerd, G.
• Other Authors: Max-Planck-Institut für Kernphysik (MPIK), Max-Planck-Gesellschaft, AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2010
• Subjects: [SDU.ASTR.HE]Sciences of the Universe [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE]; [PHYS.ASTR.HE]Physics [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE]; [SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO]; [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO]; South Pole; South pole
• Online Access: https://hal.in2p3.fr/in2p3-00706875; https://doi.org/10.1016/J.ASTROPARTPHYS.2010.01.012

We have measured the speed of both pressure waves and shear waves as a function of depth between 80 and 500 m depth in South Pole ice with better than 1% precision. The measurements were made using the South Pole Acoustic Test Setup (SPATS), an array of transmitters and sensors deployed in the ice at the South Pole in order to measure the acoustic properties relevant to acoustic detection of astrophysical neutrinos. The transmitters and sensors use piezoceramics operating at ˜5-25 kHz. Between 200 m and 500 m depth, the measured profile is consistent with zero variation of the sound speed with depth, resulting in zero refraction, for both pressure and shear waves. We also performed a complementary study featuring an explosive signal propagating vertically from 50 to 2250 m depth, from which we determined a value for the pressure wave speed consistent with that determined for shallower depths, higher frequencies, and horizontal propagation with the SPATS sensors. The sound speed profile presented here can be used to achieve good acoustic source position and emission time reconstruction in general, and neutrino direction and energy reconstruction in particular. The reconstructed quantities could also help separate neutrino signals from background.