|
The largest neutrino observatory in the world has just been completed. It's called IceCube, and is made up of 5504 sensors, located within, and on the surface, of a 1 cubic kilometre volume of ice.
The IceCube project began in 1999, and in the last ten years has seen the collaboration of a number of nations, including the USA, that through the National Science Foundation, contributed 242 million dollars (out of a total cost of 279 million). The project is managed by the University of Wisconsin-Madison, where the principal investigator, Francis Halzen, is based.
IceCube is made up of 86 large bore holes cut vertically into the ice of the South Pole, near the National Science Foundation's Amundsen-Scott South Pole Station. Within each hole (made with the Enhanced Hot Water Drill, built at the physical sciences laboratory in Stoughton, Wisconsin, and able to cut through a kilometre of ice in less than a day) there are 60 sensors down to a depth of between 1450 and 2450 metres. At the top of each hole are another 4 sensors.
IceCube is designed to detect the faint light pulses emitted when neutrinos collide with the atomic nuclei in the water molecules that make up the ice. Because neutrinos interact only very rarely with matter, a very large detector is needed to increase the probability of observing an event. The Antarctic ice is also extremely transparent, and this helps in the detection of the light emitted.
Unlike other scientific instruments used in astrophysics, a neutrino detector can collect data even before being finished, and in fact, IceCube has been doing so since 2005, providing precious information on solar neutrinos and those produced by cosmic rays hitting the atmosphere.
Now that all the sensors are in place, researchers expect to reach a level of sensitivity that will allow the detection of neutrinos derived from the formation of neutron stars and black holes, both within our own galaxy and in extragalactic objects.
|
