1996 AMANDA
Papers 1996 AMANDA
PapersImplications of Optical Properties of Ocean, Lake, and Ice for Ultrahigh-energy Neutrino Detection
by P.B. Price (1996).
The collecting power and imaging ability of planned ultrahigh-energy neutrino observatories depend on wavelength-dependent absorption and scattering coefficients for the detector medium. Published data are compiled herein for deep ice at the South Pole, for deep fresh water at Lake Baikal, and for deep sea water. The effective scattering coefficient is smallest for the clearest deep-ocean sites, whereas the absorption coefficient is an order of magnitude smaller for deep ice than for the ocean and lake sites. The effective volume per detector element as a function of energy is calculated for electromagnetic cascades produced by electron-neutrinos interacting at the various sites. It is largest for deep bubble-free ice, smallest for shallow bubbly ice, and intermediate for lake and sea water. The effective volume per element is calculated for detection of positrons resulting from capture of few-MeV supernova neutrinos by protons in the medium. This volume is proportional to the absorption length and independent of the scattering length; it is larger for ice than for sea or lake water.
1995-96 Results for the AMANDA Neutrino Observatory
by the AMANDA collaboration (P.B. Price et al.), to appear in Proceedings of the Venice Workshop on Neutrino Telescopes (1996).
At the AMANDA South Pole site, four new holes were drilled to depths ~2050 to 2180 m and instrumented with 86 PMTs at depths ~1520 to 2000 m. 79 of the PMTs are working, with 4-ns timing resolution and noise rates ~300 to 600 Hz. Various diagnostic devices were deployed and are working. An observed factor ~10^2 increase in scattering length and a sharpening of the distribution of arrival times of laser pulses relative to measurements at 800-1000 m showed that bubbles are absent at depths > 1500 m. Absorption lengths are ~100 to 200 m at wavelengths in the blue and UV to 337 nm. Muon coincidences are seen between the SPASE air shower array and the AMANDA PMTs at 800-1000 m and 1500-1900 m. The muon track rate is ~30 Hz for 8/3 triggers and ~10 Hz for 10/3 triggers. The present array is the nucleus for a future expanded array.
by C. Spiering, to appear in Proceedings of the 31st Rencontres de Moriond (1996).
by F. Halzen, to appear in Proceedings of the Venice Workshop on Neutrino Telescopes (1996).
The objective of neutrino astronomy, born with the identification of thermonuclear fusion in the sun and the particle processes controlling the fate of a nearby supernova, is to build instruments which reach throughout and far beyond our Galaxy and make measurements relevant to cosmology, astrophysics, cosmic-ray and particle physics. These telescopes will push astronomy to wavelengths smaller than 10^-14 cm by mapping the sky in high-energy neutrinos instead of high-energy photons to which the Universe is partially opaque. While a variety of collaborations are pioneering complementary methods by building neutrino detectors with effective area in excess of 0.01 km^2, we show here that the science dictates 1 km^2, or a 1 km^3 instrumented volume, as the natural scale of a high-energy neutrino telescope. The construction of a high-energy neutrino telescope therefore requires a huge volume of very transparent, deeply buried material such as ocean water or ice, which acts as the medium for detecting the particles. We will speculate on its architecture. The field is immersed in technology in the domain of particle physics to which many of its research goals are intellectually connected. With several thousand optical modules the scope of constructing a kilometer-scale instrument is similar to that of experiments presently being commissioned such as the SNO neutrino observatory in Canada and the Superkamiokande experiment in Japan.
by J. Bahcall and F. Halzen (1996).
Over the last three decades neutrino astronomy has developed into an experimental science. This fledgling discipline already has to its credit two of the most remarkable experimental discoveries of the past decade: the conclusive detection of solar neutrinos and the observation of neutrinos produced by the gravitational collapse of a star in the Large Magellanic Cloud. Large new detectors of solar neutrinos are poised to exlpore new physics or exotic behavior of the sun. Since 1993 physicists have deployed detectors in natural water and in ice with the ultimate goal of constructing kilometer size neutrino telescopes that will scan the sky for astronomical sources of neutrinos that lie far beyond the sun.