The underground hunt for neutrinos
If you want to detect neutrinos, you must go to places that other cosmic particles cant reach - far beneath the earth. Here is an overview of the world's biggest neutrino experiments.
Fast and hard to catch
Neutrinos are tiny electrically neutral particles. They cannot be deflected by magnetic fields and react only very weakly to gravity. This enables them to travel through space, the atmosphere and the earth without much difficulty. They actually travel through our entire planet Earth as if there was nothing stopping them.
Huge detectors deep in the mountain
Some neutrinos are affected by the journey, though. That's what this year's Nobel Prize winners in physics have shown: Takaaki Kajita and Arthur McDonald found out that the particles change their character - they oscillate. Kajita did his research here, at the Super-Kamiokande detector in Japan: a water tank more than 120 feet deep and filled with detectors 3000 feet deep in the mountain.
Perfect research conditions in permafrost
The largest neutrino-telescope of the world is the Ice-Cube, finished in Antarctica under the U.S. Research Station Amundsen-Scott in 2010. Its detectors are able to find neutrinos that come from outer space. The detectors are hidden deep below the ice-shield to prevent interferences from other celestial particles.
Optical sensors on long cables
Unlike in the Super-Kamiokande experiment, the detectors of Ice-Cube are not located next to each other. Each individual glass-encapsuled sensor hangs on a wire that's between one and more than two miles long. The holes have been melted into the ice with hot water. The data from the sensors is being fed into a central control station.
From the particle accelerator to the detector - all the way through Europe
The European Organisation for Nuclear Research (CERN) counts neutrinos it sends out itself. From its particle accelerators at the Swiss-French border near Geneva it shoots neutrinos right into the center of the Italian Apennines. There, in the Gran-Sasso mountain range, detectors record the impact.
Almost as fast as light
Neutrinos travel through space and rock nearly at the speed of light - but not quite. That's the reason there was much excitement at CERN's Neutrinos to Gran Sasso (CNGS) experiment: researchers measured neutrinos that were faster than light. In the end, however, the theory of relativity stood the test of time. There was a small but important fault in the measuring.
A wall of detectors
The detectors at the Gran-Sasso are packed tight, because the neutrino ray from Geneva is well focused. At its source, the physicists shoot protons at a graphite target. A lot of different elementary particles are being generated by the collisions. Most don't get very far. Only the neutrinos stay on course and make it to Italy.
Neutrino research is an international task
Besides Europe, the U.S. and Japan, China, Canada, South Korea and India are also running their own neutrino experiments. The Indian Neutrino Observatory is currently being built in the middle of this mountain. A huge magnet weighing in at 50,000 metric tons is at the heart of the project. The particle physicists want to go to the physical limit of what has so far been possible with neutrinos.
A game of neutrino pool
The Indian researchers want to find out how other particles react when being hit by neutrinos. They compare the experiment to a game of pool - with the exception that they do not see the white ball (the neutrino). When being hit, the other particles will move in various directions, providing the researchers with information about the the mysterious neutrinos.