The Antarctic Neutrino Camera Is About to Get Much, Much Bigger

The University of Wisconsin's IceCube neutrino detection system has been quietly operating amid Antarctica's barren tundra for more than four years now. In that time, the fledgling detector has captured more than 100 cosmic neutrinos, many of which originated far outside our Milky Way galaxy. And if project leaders get their way, its imaging quality is about to improve by an order of magnitude.

The IceCube neutrino detector has been in operation since 2010. It utilizes kilometer-long strings of sensitive optical sensors buried in regular 125 meter intervals across the ice sheet to catch a glimpse of rarely interacting cosmic particles known as neutrinos. The individual sensors operate much like a digital camera's pixels do, lighting up when exposed to incoming energy to create a composite view of the area's neutrino strikes. Well, technically, the incoming neutrino interacts with the surrounding ice to produce a muon. As the muon travels through the ice, it generates a tiny shockwave within the frozen lattice and emits Cherenkov radiation, which one of the 5,000 or so detectors actually senses.


"The more you have, the clearer the picture gets," University of Wisconsin physicist Francis Halzen said as he argued for an expansion of the program at a recent workshop. "To see several neutrinos come from the same source, you are likely to need well above one thousand."

Speaking of a clearer picture, the research team recently discovered that the ice sheet they're operating on is optically more clear than they originally believed. This means that the current 125 meter spacing between strings could be effectively doubled to 250 meters, allowing the team to capture a larger image without much added expenditure. And to compensate for the loss in sensor density, the team hopes to add as many as 120 new strings over the next six years, installing 20 of them annually with an updated version of their custom hot-water drill.

"We can do this for about the same amount of money we spent on the original array," Halzen says. They just need to get the National Science Foundation, which helps fund the program, on board. [Symmetry Magazine]


Top Image: S. Lidstrom, NSF

This Subterranean Telescope May Have Just Seen Humanity's First Cosmic Neutrino

Catching a glimpse of even regular neutrinos—low-energy particles generated in the atmosphere—is difficult enough, but spotting a "cosmic neutrino" left over from the Big Bang has been downright impossible. That is until this cubic kilometer buried under Antartica's frozen wastes started looking.

Known as the IceCube Neutrino Observatory, this $279 million telescope is located under the Amundsen-Scott South Pole Station in Antarctica. Since its completion in 2010, IceCube has been searching for evidence of the cosmic neutrino via an array of thousands of sensors hung in cascading lines under the ice.


Just as its predecessor, the Antarctic Muon And Neutrino Detector Array (AMANDA), did, IceCube consists of spherical optical sensors called Digital Optical Modules (DOMs), each with a photomultiplier tube (PMT). In all, 86 strings containing 60 DOMs apiece and a total of 5,160 PMTs have been hung a depths ranging from 1,450 to 2,450 meters. IceCube researchers leveraged a unique hot water drill to quickly bore through the ice when installing the array.

When a weakly-interacting neutrino does manage to strike the nucleus of an atom in the ice, the resulting energy release creates a brief flash that is picked up by the DOM and transmitted to a data collection station on the surface. The system detects roughly 100,000 neutrino strikes annually but, until last month, all of them were of the atmospheric variety. In April, IceCube detected a pair of strikes—nicknamed Bert and Ernie—with energy signatures in the TeV range, suggesting an extraterrestrial origin. Since then, the system has spotted an additional 26 potential cosmic neutrino strikes.


The data must still be analyzed and verified by the scientific community but if these really are what researchers think they are, we could soon gain new insight into conditions present mere seconds after the Big Bang. [University of Wisconsin-Madison - UPI - Wiki 1, 2 - Images: Nasa-verve DOM: Amble]