IceCube Neutrino Observatory

The IceCube Neutrino Observatory is a neutrino telescope that is currently being built at the Amundsen-Scott South Pole Station. IceCube is being constructed in deep Antarctic ice by deploying thousands of PMTs (photomultiplier tubes) at depths of 4750 to 8000 feet. These spherical optical sensors are deployed on strings of sixty modules each, into holes melted by hot water drilling. Since 2005, 59 strings have been deployed and installation is expected to be complete by 2011. The strings are only deployed during the Austral summer season (October – February).

The main goal of the IceCube experiment is to detect neutrinos in the high energy range (measured in electron volt). These neutrinos are detected by rare instances of a collisions between a neutrino and an atom within the ice. It is estimated that these collisions can be detected about one thousand times per day when the IceCube is fully constructed. Almost all detected products of the initial collision will be muons (an elementary particle with negative electric charge and spin of 0.5). Most penetrating particles do not make tracks in the ice long enough to give definitive results. The experiment will be most sensitive to the flux of muon neutrinos through the volume of detections.

Many muons that may be detected are created by cosmic rays impacting the atmosphere above the detector and as such can be rejected easily as they are traveling downwards. Most of the remaining (up-going) neutrinos come from cosmic rays hitting the far side of the Earth. However, there may be some unknown fraction of neutrinos produced from some other astronomical sources. There are some predictions of possibly the detection of 75 up-going neutrinos per day in the fully constructed IceCube detector. These arrival directions are the points with which the IceCube telescope maps out the sky. Direction and energy output of incoming neutrinos is estimated from its collision by-products. Unexpected excesses in energy or from certain directions can indicate an extraterrestrial source.

Although IceCube is expected to detect only a few neutrinos (compared to traditional telescopes that detect higher numbers of photons), it should be able to produce very high resolutions in the ones it does find. The first neutrinos were believed to have been detected on January 29, 2006. Over several years of operation, it could produce a flux map of the northern hemisphere similar to existing maps like that of the cosmic ray background. Data from IceCube could also be used in conjunction with cosmic ray detectors like HESS or MAGIC.

Photo Copyright and Credit