Detecting Neutrinos at McMurdo Station
23.04.2010 - Atmosphere & Space, Antarctic
During this past Antarctic season, the first prototype for the proposed Antarctic Ross Ice Shelf Antenna Neutrino Array (ARIANNA) of neutrino detectors was successfully installed in Antarctica. A team from Berkley Lab’s Nuclear Science and Engineering Divisions spent nearly two weeks at McMurdo Station installing what they hope will be the first of up to 10,000 other arrays within a 30 km radius of the station.
The purpose is to detect neutrinos in the hope of determining where the cosmic rays (which are actually energetic particles, mostly protons and helium nuclei) bombarding the Earth originate in space. Some of these particles come from our sun. However the majority come from unknown sources within a “nearby” 225 light year range of Earth.
Being electrically charged, the most energetic cosmic rays are forced to bend as they travel through interstellar magnetic fields, making it difficult to trace their origin. Yet by looking at neutrinos – nearly massless subatomic particles which are created as cosmic rays pass through the cosmic microwave background of the universe – scientists hope to be able to pinpoint sources capable of producing cosmic rays in the local universe. Since they can pass through all matter – even stars – and have no electrical charge for magnetic fields to affect, they travel in a straight line, it’s possible to determine where they originate.
Neutrinos are very difficult to detect, however. Yet the Ross Ice Shelf provides a perfect environment for detecting neutrinos. The interface between ice and liquid water below acts as an excellent surface for reflecting radio waves (the detectors monitor for Cherenkov radiation, which has wavelengths within the radio wavelengths). Using radio antennas buried in the snow on top of the ice, ARIANNA will observe the shower of electrons, positions and other particles produced when a neutrino interacts with the ice below a detector. This will help them trace the source of the neutrinos.
So far the team has not managed to detect a single neutrino, but with just one detector installed so far this is understandable. They hope to add a group of up to seven more in the next stage.
