Hundreds of astrophysicists were in Madison, Wisconsin, Wednesday through Saturday of last week to celebrate the completion of the IceCube neutrino detector — on time and on budget. (This is a pretty awesome achievement in astronomy experiments.) While talks on Wednesday and Thursday were geared toward general science in Antarctica, the presentations on Friday and Saturday related to more-general particle astrophysics and cosmology.
Members of the IceCube team pose in front of the deployment tower after they complete the huge neutrino detector in Antarctica. They placed the last string December 18, 2010. // Photo by NSF/C. Carpenter
Friday had a few sessions about the history of neutrino detectors and what processes create these “ghostly” particles. (Scientists refer to neutrinos as “ghosts” because they interact extremely weakly with matter and have tiny masses.) The first proposal to utilize water or ice for a neutrino detector was published in 1960. Nearly 2 decades later, the first underwater neutrino experiment began construction; however, it was never completed due to electronic problems. This project, DUMAND (Deep Underwater Muon And Neutrino Detector Project), was supposed to be located in the Pacific Ocean. While DUMAND didn’t work as planned, researchers did gain knowledge about how the detectors operate in water, or ice.
Scientists proposed the Antarctic Muon And Neutrino Detector Array (AMANDA) in 1988. This project, the precursor to IceCube, began construction in 1991, and was completed in 2000. AMANDA then became part of the next-generation neutrino ice detector: IceCube.
The National Science Foundation gave this 0.23-cubic-mile (1 cubic kilometer) neutrino experiment the go ahead in 2004. Scientists installed the first detector string of 60 digital optical modules (DOMs) in January 2005. They installed the 86th string — the last one — December 18, 2010. Scientists say 98 percent of the 5,160 optical detectors are working properly, which is a good thing, as all DOMs are now frozen within the Antarctic ice.
IceCube is looking for high-energy neutrinos. These particles are created in the same astrophysical processes that produce cosmic rays. Scientists, however, are unsure of what sources can create high-energy cosmic rays and neutrinos. Antarctic polar ice is an ideal medium for detecting neutrinos: It is pure, transparent, and has no radioactivity. So, the goal is to collect high-energy neutrinos and trace their paths back to their sources.
The talks both Friday and Saturday were filled with congratulatory remarks to the IceCube team. It took a lot of new technology and hard work to get this project up and running on time. Here’s hoping the huge experiment will do equally huge science in the next few years.
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