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This week, workers and researchers from UW-Madison completed what may have been the most challenging construction job in the university's history, 8,000 feet deep in the ice under the South Pole.

They buried the last of 86 strings of detectors that are the heart of a massive scientific instrument called IceCube.

It is the world's largest neutrino detector, under construction since 2004 and designed to capture data on the high-energy particles from deep space as they zip through the crystalline Antarctic ice and collide with the atomic nuclei of frozen water.

Studying those particles may give us a new understanding of everything from black holes, exploding stars and dark matter, to the origin of the universe in the Big Bang.

Francis Halzen, the principal scientific investigator of the $272 million project, can talk forever about the potential mysteries that IceCube is likely to help solve. But last Monday he was more like a teenager on Facebook, sitting in IceCube's Madison office and intently watching a live video feed from the South Pole as workers guided the 83rd string of basketball-size detectors into the ice. 

That left three strings to deploy, and the last of those was lowered into its frigid, 8,000-foot-deep resting place Saturday, Halzen said.

He said the milestone is deeply satisfying but also "a huge relief."

"If you would have told me in January 2005 when we deployed the first string that in 2010 we would be installing the last, all without mishap, I would have said that's impossible," Halzen said.

Considering the conditions, mishaps seemed almost a certainty. 

The construction season at the South Pole is just three months long during the Southern Hemisphere's summer, which is opposite of ours. 

The average summer temperature? Minus 18.

Plus, the workers toil at 10,000 feet above sea level, which makes walking more difficult, let alone wrestling around heavy cables, pipes and other equipment.

Another challenge is the bone-dry air, which causes the ends of fingers to split and bleed. 

One of the staples in work crew pockets is Super Glue, used to seal and treat those painful wounds.

Karl A. Erb, the director of the National Science Foundation's Office of Polar Programs, praised the researchers and workers who built the unique detector under such difficult conditions. 

Most of the money for the project came from the National Science Foundation. 

In addition to Wisconsin, workers from Germany, Belgium and Sweden helped build the detector, and the study of data from the instrument will involve more than 250 scientists from 36 institutions in the U.S. and around the world.

Halzen said IceCube already has been generating data. High-energy neutrinos are much sought after by scientists because they have almost no mass and pass through objects, whether a planet or a person, almost unchanged from what they were like when they originated in, say, a black hole. 

But in the massive and icy trap of IceCube, some neutrinos will collide with atoms of ice and eject another particle called a muon traveling in the same direction as the neutrino. 

>The muon, however, will leave a trail of blue light, which IceCube's strings of sensors will be able to detect from almost a football field away.

By tracing the path of that flash of light backward, scientists will be able to determine the origin of the neutrino and unlock a wealth of information about the particle.

Halzen said the instrument must be calibrated before it can work at full capacity. That involves studying the passage of other particles through the ice to understand better the flaws and quirks of the ice, what Halzen calls the "optics" of the ice. 

Such detail will help the scientists more accurately understand and interpret the neutrino data when it starts flowing more regularly. 

The detector was built at the South Pole because of the clarity of the ice there.

Already, Halzen said, the study of the ice has revealed new scientific knowledge unrelated to the neutrino research.

The ice at the bottom of the 8,000-foot holes holding the sensors is 100,000 years old.

From material trapped in the ice, researchers have been able to document the eruption of Antarctic volcanoes that exploded 10,000 years ago.

Such intriguing finds, Halzen said, only hint at what secrets will be revealed when study turns from terrestrial science to the exploration of deep space. 

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