IceCube | Attempting to catch the rare neutrino that crashes into an atom of ice.

What is a Neutrino? The common definition talks about elementary particles that often travel close to the speed of light. Neutrinos are electrically neutral, and are able to pass through ordinary matter almost undisturbed and are thus extremely difficult to detect. Neutrinos have a minuscule, but nonzero mass.

As pointed at Seeds Magazine:

For decades physicists have suspected that neutrinos hold some of the universe’s darkest secrets. Determining their behavior and where they came from could tell rich stories of the early universe and potentially illuminate the curious nature of dark matter.

The interesting about these particles are that they are extremely difficult to detect. As they are so evasive there has been many attempts to a deeper understanding of their behaviour. Because neutrinos are only weakly interactive with other particles of matter, neutrino detectors must be very large in order to detect a significant number of neutrinos and most of them are often built underground to isolate the detector from cosmic rays and other background radiation; e.g. the Sudbury Neutrino Observatory, located 6,800 feet [about 2 km] underground in Vale Inco’s Creighton Mine in Sudbury, Ontario, Canada. The detector was designed to detect solar neutrinos through their interactions with a large tank of heavy water. The detector turned on in May 1999, and was turned off on 28 November 2006:


Construction of the geodesic sphere that surrounds the acrylic cavity at the Sudbury Neutrino Observatory [Lawrence Berkeley Nat’l Lab – Roy Kaltschmidt, photographer]

But now, we’re going to focus on the IceCube Neutrino Observatory, because now it becomes the largest neutrino telescope in the world and there, a team of pioneering researchers has buried thousands of sensors miles deep into the ice at the bottom of the Earth, all in an attempt to catch the rare neutrino that crashes into an atom of ice. The IceCube is currently under construction at the Amundsen-Scott South Pole Station, where “The ultra-transparent Antarctic ice itself is the detector.” in words of Francis Halzen, Principal Investigator of IceCube.

The team uses a massive drill that is constantly fed scalding-hot water to bore more than 2.5 kilometers into the huge block of ice that makes up the South Pole. The amount of ice melted per hole is approximately 200,000 gallons. The firn drill, drill head and weight stack are stored and used at the drill tower. The whole structure is moved after each hole is drilled and deployed.


IceCube: Drill going down the hole. NSF


IceCube: The drill tower. NSF

They explain why the South Pole at the Antartic has been choosen for its construction:

Although trillions of neutrinos stream through your body every second, none may leave a trace in your lifetime. We actually use large volumes of ice below the South Pole to watch for the rare neutrino that crashes into an atom of ice. This collision produces a particle—dubbed a “muon”—that emerges from the wreckage. In the ultra-transparent ice, the muon radiates blue light that is detected by IceCube’s optical sensors.

Architects and urbanist are mostly interested in how cities develop on the planet surface, but now we’re also interested in what is happening down there at the Earth’s entrails. It’s well known that under our feet there is a huge network of underground infrastructures that are connected, as tunnels, underground dwellings, oil pipelines and even catacombs. But is also interesting to see how science and architecture meets down under. A good example is the CERN particle physics laboratory, situated in the northwest suburbs of Geneva on the Franco–Swiss border, with the Large Hadron Collider tunnel located 100 metres underground in the region between the Geneva airport and the nearby Jura mountains or there is also the Lake Baikal Neutrino Telescope, now being constructed for deep underwater neutrino research.


IceCube: Drill site and seasonal equipment site. NSF


IceCube: Tower site and SES. NSF

The history of underground detectors for natural neutrino fluxes started with the pioneering detectors in India [1965], South Africa [1965] and in the Northern Caucasus [1978] and led to armed giants with effective areas of 1000 square meters [MACRO, Italy], and sensitive volume of more than 20000 tons [SUPERKAMIOKANDE, Japan]. Now, talking about the IceCube, professor Halzen answers to the question:

In the past six months, what has been the most exciting advance or breakthrough you’ve had in the lab?

[Almost] completing the detector. This is about proof-of-concept technology. We found a way to build a kilometer-scale particle detector. The ultra-transparent Antarctic ice itself is the detector. We’ve surrounded a large volume of it, one kilometer on each side, with more than 5,000 light sensors. It may not be a very good one, but it is by far the biggest ever built and that is the goal.

Just to have an idea of the real dimensions of each hole, they pointed that the travel time from Los Angeles to the South Pole is approximately 48 hours… Well, the average time to drill a hole for IceCube is approximately 48 hours, and the average depth of an IceCube hole that is 2.452 m.


IceCube: DOM Descending down hole. NSF


IceCube: Trenching through snow and placing cable on surface. NSF

The south pole is basically an enormous glacier and consists almost entirely of ice and the weight of these glaciers in Antarctica are compressing the land under them, if the glaciers were removed the land of Antarctica would slowly rise over the period of hundreds of years. These is the landscape in which the IceCube is being constructed. Is simply striking to read that once the detectors are frozen in the ice, they will stay there for 25,000 years or so. That is approximately the amount of time it will take for that portion of the ice to migrate to the coast of Antarctica.

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IceCube Neutrino Observatory web-site and BLOG. On twitter, the IceCube is @uw_icecube.
Highly recommended article with slideshow at Seed Magazine: Butterfly Nets for Ghosts
About the images: “This material is based upon work supported by the National Science Foundation under Grant Nos. OPP-9980474 [AMANDA] and OPP-0236449 [IceCube], University of Wisconsin-Madison”

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