So Much for So Little: Giant Experiments Seek Out Tiny Neutrinos [Slide Show]
It takes a massive detector to spot the remarkably elusive particle
![So Much for So Little: Giant Experiments Seek Out Tiny Neutrinos [Slide Show]](https://www.scientificamerican.com/sciam/cache/file/81977579-BFA8-4D20-9969E2578AE9F4CB.jpg?w=590&h=393)
So Much for So Little: Giant Experiments Seek Out Tiny Neutrinos [Slide Show]
- ICE FISHING: To build the IceCube array, workers had to drill deep into the ice, then lower strings of sensors called digital optical modules (DOMs) such as the one pictured above. Each of the 86 sensor strings holds 60 DOMs, which are now frozen into place up to 2.5 kilometers below the surface. IceCube Collaboration/NSF
- SPACED OUT: A truly giant neutrino detector recently began full operation in Antarctica. The IceCube Neutrino Observatory uses a cubic kilometer of ice as its detector material; a network of sensor chains has been embedded in the ice. The colored dots on the photo above mark the location of a vertical string of sensors. A neutrino interacting with the ice produces a charged particle called a muon that in turn gives off blue light as it traverses the detector. IceCube’s chains of sensors register that light and allow physicists to track the arrival direction of the neutrino. Haley Buffman/NSF & Jamie Yang/NSF
- EYES PEELED: Like Double Chooz, the Daya Bay Reactor Neutrino Experiment in China uses near and far detectors to measure the oscillations of neutrinos emanating from a nuclear power plant. The photo above shows the photomultiplier tubes within the Daya Bay detectors, which register the collision of a neutrino with the fluid filling the detector cylinder. Lawrence Berkeley National Lab/Roy Kaltschmidt, photographer
- POWER SOURCE: Particle accelerators are not the only place physicists can tap into a pure, steady stream of neutrinos. Nuclear reactors also emit large quantities of neutrinos, and a number of experiments have set up shop nearby to measure how they propagate. The Double Chooz experiment in France, above, comprises two detectors: a near detector 400 meters from the reactors and a far detector one kilometer from the power plant. Comparing the number of hits at each detector allows physicists to determine how many have changed flavor between the two distances. © CEA/DSM/IRFU-DCOM/L.Colombel
- FAR OUT: It doesn’t look like much, but this remote site in northern Minnesota will soon house a 15,000-metric-ton particle detector to register neutrinos from Fermilab, more than 800 kilometers away. The planned NOvA experiment seeks to explore the rare oscillation of muon neutrinos into electron neutrinos over large distances. Fermilab, NOνA collaboration
- DEEP DOWN: Buried underground in the inactive Soudan iron mine in Minnesota, the 5,400-metric-ton octagonal MINOS detector picks up neutrinos from Fermilab in Illinois, 735 kilometers away. The particles leave Fermilab as a nearly pure beam of muon neutrinos, but most have changed into tau neutrinos by the time they reach the MINOS detector. To the right of the detector is a neutrino-inspired mural by artist Joseph Giannetti. Haley Buffman/NSF and Jamie Yang/NSF
- TANKING IT: The Super-Kamiokande detector in Japan, an underground tank that holds 50 million liters of water, captures neutrinos that emanate from a particle accelerator nearly 300 kilometers away. When a neutrino hits the detector, it can produce charged particles, whose high speed through the water emits a flash of light, triggering phototubes mounted in the walls of the Super-K tank. The experiment, known as T2K (Tokai to Kamioka), investigates muon neutrinos transforming into electron neutrinos—one aspect of the so-called oscillation process by which neutrinos change particle “flavors.” Kamioka Observatory/ICRR (Institute for Cosmic Ray Research)/University of Tokyo
