On Dec. 4, 2012, the IceCube Observatory in Antarctica at the Amundsen-Scott South Pole Station, detected an event now known as Big Bird, a neutrino with an energy exceeding 2 quadrillion electron volts (PeV). To put that in perspective, it’s more than a million million times greater than the energy of a dental X-ray packed into a single particle thought to possess less than a millionth the mass of an electron. Big Bird was the highest-energy neutrino ever detected at the time.
Where did Big Bird come from? The best IceCube position only narrowed the source to a patch of the southern sky about 32 degrees across, equivalent to the apparent size of 64 full moons.
“It’s like a crime scene investigation”, says Matthias Kadler, a professor of astrophysics at the University of Würzburg in Germany, “The case involves an explosion, a suspect, and various pieces of circumstantial evidence.”
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This CSI is the specialty of IceCube Neutrino Observatory, which is being upgraded to better understand the properties of neutrinos: “Together with measurements of other signals from the depth of the universe, such as cosmic rays, high-energy gamma quanta, or gravitation waves, the IceCube upgrade experiment will contribute decisively to solving the mysteries of physics of highest-energy processes in our universe,” says Haungs.
In 2017, the IceCube Neutrino Observatory that is part of the US-American Amundsen-Scott South Pole Station found convincing proof of a first source of high-energy cosmic neutrinos. Now, the observatory is being upgraded. New state-of-the-art instrumentation will dramatically boost IceCube’s performance at the lowest energies, increasing the samples of atmospheric neutrinos by a factor of ten, and will enhance the pointing resolution of astrophysical neutrinos.
As a result of this upgrade, IceCube will yield the world’s best measurements in neutrino oscillations as well as critical measurements that could provide evidence for new physics in the neutrino sector.
The IceCube detector is being extended to also measure lower energies and, hence, the properties of neutrinos with so far unreached accuracy. In this way, understanding of basic processes in the universe, such as physics in galactic nuclei, will be enhanced.
IceCube serves to measure high-energy neutrinos in an ice volume of one cubic kilometer. As neutrinos proper do not emit any signals, the tracks of myons are measured precisely. Myons are elementary particles sometimes produced by the interaction of neutrinos with ice. Contrary to neutrinos, myons carry an electric charge. On their way through the ice, they produce a characteristic light cone, the so-called Cherenkov radiation. Highly sensitive detectors measure this blue radiation. Currently, 5160 detectors on 86 cables are installed 1500 to 2500 m deep in the ice.
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“Within the framework of the IceCube upgrade project, seven additional cables will be installed deep in the ice in the middle of the existing lines. They are equipped with 700 upgraded detectors,” says Dr. Andreas Haungs, Head of the IceCube group of KIT. “The ice in and around the detector is highly transparent, which is ideal to study the properties of very quick, i.e. relativistic, particles.”
The planned IceCube upgrade detector will consist of two different types of optical modules to test two technologies for the future tenfold enlargement of IceCube, IceCube-Gen2. Compared to previous modules, the multi-Pixel Digital Optical Module (mDOM)mDOM has a much larger and segmented detection area, as a result of which a much higher sensitivity is reached.
The IceCube Neutrino Observatory is located directly at the geographic South Pole. The science program is executed by the international IceCube collaboration of more than 300 scientists from 52 institutes in twelve countries.
The Daily Galaxy, Sam Cabot, via Karlsruhe Institute of Technology (KIT)
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