Fishing for neutrinos in Lake Baikal
9 May 2001
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Lake Baikal is not only the deepest (1.6 km) freshwater lake in the world, it is the only one that is also a telescope for cosmic neutrinos.
The neutrino telescope, known as NT-200, is located 3.6 km from the
shore and at a depth of 1.1 km, and consists of 192 "optical modules"
that detect light produced by the interactions of the elusive
neutrinos. In this image, members of the NT-200 team take advantage of
the thick layer of ice during the winter months to deploy a string of
modules. Here a pair of the modules, each containing a phototube
35cm in diameter, is being lowered into the water below the ice. The
spheres are made from glass but are designed to withstand the pressure
at depths of up to several kilometeres.
NT-200 came into full operation in April 1998. It detects
high-energy particles known as muons, as they come upwards through the
water, emitting light known as Cerenkov radiation. These muons must have been produced by neutrinos created when cosmic rays collided with the atmosphere on the opposite side of the Earth!
Credit: Christian Spiering, DESY-ZEUTHEN
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