University of Wisconsin-Madison

IceCube Explained

IceCube is a unique telescope at the South Pole. Most optical telescopes look at photons, but IceCube looks for evidence of a more mysterious particle called a neutrino. Because of this, it is referred to as a neutrino telescope or neutrino detector. Using an optical telescope to look at the Universe is like taking a photo, but looking at the Universe with a neutrino telescope is similar to taking an X-ray.

Neutrinos

Neutrinos are very small, nearly massless particles that come from a variety of sources. They come from the sun, radioactive decay, cosmic rays, and violent events in the galaxy such as exploding stars. Exploding stars, or supernovas, release very large amounts of neutrinos.


Animation of a neutrino passing through the detector.

IceCube is focused on seeing high energy neutrinos, which can help us understand where cosmic rays come from and learn more about gamma ray bursts and supernovae, the identity of dark matter, and the ability of neutrinos to oscillate, or change type. IceCube is a tool for exploration. Already it has changed the way we think of the Universe.

Since neutrinos have a very small mass, they are hard to detect. IceCube uses a large volume of ice at the South Pole in Antarctica to hold basketball sized detectors called digital optical modules, or DOMs. Altogether, there are over 5,160 DOMs in the ice and an additional 344 on IceTop, a complimentary detector on the surface of the ice.

South Pole Science

It may seem strange to use the ice at the South Pole, but there are several reasons why it is an excellent location. First, the ice is very clear. IceCube is buried very deep in the ice, about 1500 to 2000 meters, or from 1 to 1.5 miles, below the surface. At that depth, pressure has pushed all the bubbles out, which means it is easy for the DOMs to record neutrino interactions.

Second, it is very dark in the ice. This is important because when a neutrino interacts with an atom of ice, a particle called a muon is produced. The muon radiates blue light that is detected by the DOMs, and the DOMs can only detect this light in a very dark environment. The direction and intensity of the light allows us to determine where the neutrino was coming from in the Universe.

Finally, the last great thing about the ice at the South Pole is that there is a lot of it! The IceCube neutrino detector is enormous. It uses a cubic kilometer of ice and is the largest neutrino detector in the world.

IceCube in Scale: The dashed lines above represent the portion of the cables that have DOMs attached.
IceCube in Scale: The dashed lines above represent the portion of the cables that have DOMs attached.

IceCube Construction

The detector was completed in December of 2010, thanks to the hard work of the IceCube Collaboration and the drill teams. Building IceCube was a unique adventure and a singular engineering project.

To embed DOMs in the ice, we used a special hot water drill. The drill was designed specifically for the IceCube project by the UW Physical Sciences Lab with a high-pressure hose that melts through the ice at astonishing speeds. Once a hole was drilled, deployment specialists carefully connected DOMs to a cable and lowered them in the hole. Each hole has 60 DOMs in it, and there are 86 holes total.

IceCube has a surface component called IceTop that houses DOMs on top of the ice, too.

The total cost of IceCube was $279 million USD. The National Science Foundation provided around $242 million for construction, and our funding partners in Germany, Sweden, and Belgium provided the rest.

IceCube was based on a pilot project called the Antarctic Muon and Neutrino Detection Array, or AMANDA. Many people from the AMANDA project are now part of the IceCube Collaboration. The IceCube Collaboration is responsible for development, construction, and analysis of data from the detector. Currently, the collaboration includes people from 43 institutions in 12 countries.