Dialogos of Eide: Antarctic Muon And Neutrino Detector Array....

Sunday, December 12, 2010

Antarctic Muon And Neutrino Detector Array....

Diagram of IceCube. IceCube will occupy a volume of one cubic kilometer. Here we depict one of the 80 strings of opctical modules (number and size not to scale). IceTop located at the surface, comprises an array of sensors to detect air showers. It will be used to calibrate IceCube and to conduct research on high-energy cosmic rays. Author: Steve Yunck, Credit: NSF

.....(AMANDA) is a neutrino telescope located beneath the Amundsen-Scott South Pole Station. In 2005, after nine years of operation, AMANDA officially became part of its successor project, IceCube.

AMANDA consists of optical modules, each containing one photomultiplier tube, sunk in Antarctic ice cap at a depth of about 1500 to 1900 meters. In its latest development stage, known as AMANDA-II, AMANDA is made up of an array of 677 optical modules mounted on 19 separate strings that are spread out in a rough circle with a diameter of 200 meters. Each string has several dozen modules, and was put in place by "drilling" a hole in the ice using a hot-water hose, sinking the cable with attached optical modules in, and then letting the ice freeze around it.

AMANDA detects very high energy neutrinos (50+ GeV) which pass through the Earth from the northern hemisphere and then react just as they are leaving upwards through the Antarctic ice. The neutrino collides with nuclei of oxygen or hydrogen atoms contained in the surrounding water ice, producing a muon and a hadronic shower. The optical modules detect the Cherenkov radiation from these latter particles, and by analysis of the timing of photon hits can approximately determine the direction of the original neutrino with a spatial resolution of approximately 2 degrees.

AMANDA's goal was an attempt at neutrino astronomy, identifying and characterizing extra-solar sources of neutrinos. Compared to underground detectors like Super-Kamiokande in Japan, AMANDA was capable of looking at higher energy neutrinos because it is not limited in volume to a manmade tank; however, it had much less accuracy because of the less controlled conditions and wider spacing of photomultipliers. Super-Kamiokande can look at much greater detail at neutrinos from the Sun and those generated in the Earth's atmosphere; however, at higher energies, the spectrum should include neutrinos dominated by those from sources outside the solar system. Such a new view into the cosmos could give important clues in the search for Dark Matter and other astrophysical phenomena.

After two short years of integrated operation as part of IceCube^[1], the AMANDA counting house (in the Martin A. Pomerantz Observatory) was finally decommissioned in July and August of 2009.