Dissertation Abstract
Measurement of acoustic attenuation in South Pole ice with a retrievable transmitter
Tosi, Delia 2010 http://icecube.wisc.edu/~detosi/
Faculty of Mathematics and Natural Sciences I, Humboldt Universitaet zu Berlin (Germany), 179 pp.
The neutrino flux generated by the interaction of high energy cosmic rays with
the cosmic microwave background is predicted to produce about 0.1 event per cubic kilometer per year. The detection of a sufficient number of events in a few years requires to instrument a volume of at least 100 cubic kilometers. The biggest detectors nowadays in construction, covering a volume of about 1 cubic kilometer, utilize optical sensors to detect the light produced by neutrino interactions; to extend this instrumentation method by the two necessary orders of magnitude is cost-prohibitive. An alternative is to use the radio or the acoustic signal generated by the neutrino-induced particle cascade, or even better, to use both of them in a hybrid detector.
Ice is a promising medium since in principle all three signals can be detected simultaneously. The growing optical experiment IceCube, located at the geographic South Pole, could be complemented with radio and acoustic sensors. A pre-requisite to do so is to measure the acoustic properties of South Pole ice. The South Pole Acoustic Test Setup (SPATS) has been designed to measure background noise, sound speed profile, transient events rate and acoustic attenuation length at that location. The system is comprised of four strings of acoustic sensors and transmitters which are installed at depths between 80 and 500 m. In addition, a retrievable transmitter (called pinger) has been developed and used in several water-filled holes.
After almost three years of operation, good progress has been achieved for all the goals. In particular, the attenuation length, one of the most important parameters for determining neutrino detection feasibility, and for which only theoretical estimates were available previously, has now been measured in situ with high confidence to be 312 plus 68 minus 47 m. In this work the hardware developed and the analysis performed to achieve this measurement are presented together with the final result.
the cosmic microwave background is predicted to produce about 0.1 event per cubic kilometer per year. The detection of a sufficient number of events in a few years requires to instrument a volume of at least 100 cubic kilometers. The biggest detectors nowadays in construction, covering a volume of about 1 cubic kilometer, utilize optical sensors to detect the light produced by neutrino interactions; to extend this instrumentation method by the two necessary orders of magnitude is cost-prohibitive. An alternative is to use the radio or the acoustic signal generated by the neutrino-induced particle cascade, or even better, to use both of them in a hybrid detector.
Ice is a promising medium since in principle all three signals can be detected simultaneously. The growing optical experiment IceCube, located at the geographic South Pole, could be complemented with radio and acoustic sensors. A pre-requisite to do so is to measure the acoustic properties of South Pole ice. The South Pole Acoustic Test Setup (SPATS) has been designed to measure background noise, sound speed profile, transient events rate and acoustic attenuation length at that location. The system is comprised of four strings of acoustic sensors and transmitters which are installed at depths between 80 and 500 m. In addition, a retrievable transmitter (called pinger) has been developed and used in several water-filled holes.
After almost three years of operation, good progress has been achieved for all the goals. In particular, the attenuation length, one of the most important parameters for determining neutrino detection feasibility, and for which only theoretical estimates were available previously, has now been measured in situ with high confidence to be 312 plus 68 minus 47 m. In this work the hardware developed and the analysis performed to achieve this measurement are presented together with the final result.