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Int'l team begins project to find neutrinos in Antarctic.

TOKYO, Feb. 15 Kyodo

A team of scientists from eight countries has begun a project to find the subatomic particles named neutrinos in the Antarctic, digging holes extending up to 2,500 meters in depth to observe neutrinos that interact in ice near the South Pole.

The team, comprising scientists from Belgium, Britain, Germany, Japan, the Netherlands, New Zealand, Sweden and the United States, has named the observatory ''Ice Cube.''

The only participant from Japan, Shigeru Yoshida, an assistant professor of cosmic-ray physics at Chiba University, said the team is trying to capture weak light generated by neutrinos when they crash into ice using about 4,800 detectors.

The team has installed 540 detectors so far to begin the observation.

The team expects to complete an observatory measuring about 1 cubic kilometer by 2009-2010 that is about 20,000 times the capacity of the gigantic underground neutrino detector named Super Kamiokande in Hida, Gifu Prefecture.

The observatory, Ice Cube, is already the world's largest neutrino detector at this point, according to the team.

Neutrinos are produced in vast numbers by the sun and other astrophysical objects by nuclear fusion before flying to the Earth.

It is hard to observe neutrinos because they pass through matter mostly without any interactions.

The observatory Super Kamiokande detects light generated by neutrinos when they interact with water molecules in an underwater tank measuring 40 meters in diameter and 40 meters in height that contains 50,000 tons of purified water.

Scientists believe there are very few numbers of high-energy neutrinos, some of which are believed to come from black holes, and believe that the observation requires a large-scale device, prompting the team to turn to the vast and transparent Antarctic ice.

So far, the team has dug a hole vertically extending from the surface of the ice, and sent down a cable equipped with 60 detectors, each placed 17 meters apart, to the depth of 1,400-2,500 meters.

The team will plant 80 holes with an interval of 125 meters in a vast hexagonal area to observe neutrinos that primarily come through the Earth from the direction of the Arctic.

Eighty percent of the 30 billion yen cost (about $255 million) is covered by the United States, while Japan and seven others cover the rest. The team uses Hamamatsu Photonics KK's photoelectron multipliers as neutrino detectors.

The team aims to detect neutrinos that have higher energy, possibly coming from black holes or big bangs outside the galaxy, than the ones found by Nobel Prize-winning Japanese physicist Masatoshi Koshiba.
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Publication:Japan Energy Scan
Date:Feb 20, 2006
Words:425
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