IceCube

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Drilling station for IceCube in December 2009

The IceCube Neutrino Observatory (or simply IceCube ) is a high-energy neutrino observatory that is part of the Amundsen-Scott South Pole Station in Antarctica.

Since 2010, in a volume of 1 km 3 High Energy - neutrinos registered when they react with components of the ice. This happens because the fast electrons , muons or tauons generated in the ice cause Cherenkov radiation , which is detected with highly sensitive optical sensors ( photomultipliers ). Scientists hope that IceCube will provide them with knowledge about the sources of the charged cosmic rays in which the neutrinos are also generated.

history

The principle used was already used in the AMANDA project (Antarctic Muon And Neutrino Detector Array) and has provided data there since 1997. On May 11, 2009, AMANDA was shut down as planned. Due to the success, the funds for the IceCube project were approved. IceCube was completed on December 18, 2010 after almost six years of construction and a decade of preparation. The first scientific results have already been achieved with the first expansion stages of IceCube in joint operation with AMANDA. The most important scientific result so far is the first observation of high-energy cosmic neutrino radiation in 2013.

The principal investigator is Francis Halzen .

On June 25, 2019, the National Science Foundation approved funding for an expansion. The existing 5160 sensors are to be supplemented by more than 700 optical modules on seven cable strands in the Antarctic summer of 2022/23. The Helmholtz Centers DESY and the Karlsruhe Institute of Technology (KIT) are supporting the construction of 430 new optical modules with a total of 5.7 million euros. This expansion should not only increase the sensitivity of the observatory, but also lower the energy threshold above which neutrinos can be detected.

technology

One of the more than 5000 light receiving probes ( Digital Optical Module , DOM for short) with 25 cm photomultiplier type R7081-02, the photocathode of which can be seen in the lower hemisphere

IceCube currently has 86 cable harnesses with a total of 5160 sensors that detect, amplify, and digitize the Tscherenkov traces of muons, electrons and tauons and then forward them to the Amundsen-Scott South Pole Station . The 677 modules from AMANDA were used in some IceCube analyzes. The photoelectron multipliers used have a reception range of 300… 650 nm wavelength with a maximum sensitivity at the blue end of the light spectrum, a quantum yield of 25% and a 10… 50 million-fold secondary electron gain. The large, roughly hemispherical cathode area of ​​550 cm 2 , which fills the lower part of the football-sized pressure-resistant glass sensor housing, is remarkable .

The cables and detectors are sunk into holes drilled with hot water, which then freeze over again; the sensors are placed at depths between 1450 and 2450 meters, where the enormous pressure compresses all the disruptive air bubbles to such an extent that they no longer play a role in the propagation of light.

functionality

The detection of muons is best suited for determining the direction of neutrinos. The extremely rare collision of a muon neutrino with a molecule causes the neutrino to be converted into a muon. The muon continues the neutrino's trail, releasing a cone of blue light, the Cherenkov radiation. This very weak light radiation is converted into measurable electrical impulses by photomultipliers . The arrival times of the light at the individual sensors can be used to calculate the direction from which the neutrino came.

Neutrin telescopes such as IceCube can also discover supernovae or contribute to the detection of dark matter . Directed radiation bursts (so-called gamma ray bursts ), which z. B. black holes in the center of a spiral galaxy play a role. In this respect, the facility and the "trappings" are an explicit example of the rapidly developing collaboration between high-energy physics and astrophysics . In contrast to charged cosmic rays, high-energy neutrinos are not deflected by cosmic magnetic fields and are hardly absorbed by matter, but they probably originate from events similar to these; they can therefore give clues to the sources of high-energy cosmic rays.

Scientific successes

In June 2013, the IceCube collaboration published the first results that indicated a non-terrestrial flux of neutrinos. Two neutrino events were found, too few to make a statistically significant statement. In November 2013, the collaboration published the follow-up measurement in the journal Science , which is considered to be evidence of non-terrestrial neutrinos. For this success, Physics World magazine awarded the “Breakthrough of the Year” prize for 2013. As reported in Science, 28 events were isolated from high-energy neutrinos between 30 TeV and 1200 TeV when the data were analyzed from May 2010 to May 2012 . Among these and the data collected in the following year were also the neutrinos with the highest energy up to then, with energies of 1000 (called Bert, as in the other events after the figures of Sesame Street), 1100 (called Ernie) and 2200 TeV (4th December 2012, called Big Bird). On June 11, 2014, a neutrino event with an even higher energy was found (2600 TeV). 2016 almost a year lasting from summer 2012 was Blazar outbreak in the galaxy PKS 1424-418 B as a likely source of Big Bird identified from comparison with the observations of the gamma-ray Space Telescope Fermi and the radio telescope project Tanami.

In cooperation with other telescopes, IceCube was able to prove the origin of a high-energy neutrino (290 TeV) for the first time in 2018. The Blazar TXS 0506 + 056, an active galaxy nucleus, 4.5 billion light years away has been identified as the probable source . It is also likely a source of cosmic rays (from high-energy protons).

Financing and cooperation

The total cost of the approximately 270 million US dollar neutrino detector comes mainly from the American science foundation NSF . The project was largely co-financed by universities and institutes in Sweden , Belgium , Germany , Great Britain , Japan and the Netherlands . The Federal Ministry of Education and Research and the DFG supported the construction of the observatory.

The IceCube team consists of approx. 300 scientists from 48 research institutions in twelve countries who continuously operate and develop the detector. In addition to researchers from the countries that have funded IceCube, scientists from Australia , Denmark , New Zealand , Canada , Japan , Switzerland and South Korea are also involved in the operation and data analysis. From Germany the German electron synchrotron DESY , the universities RWTH Aachen , HU Berlin , RU Bochum , TU Dortmund , FAU Erlangen-Nürnberg , JGU Mainz , TU Munich , WWU Münster and BU Wuppertal are involved.

See also

literature

  • Francis Halzen : Neutrino hunt at the end of the world . Spectrum of Science, May 2016, pp. 34–40.
  • Mark Bowen: The telescope in the ice - inventing a new astronomy at the South Pole. St. Martins Press, New York 2017, ISBN 9781137280084 .

Web links

Commons : IceCube  - collection of images, videos and audio files

Individual evidence

  1. ↑ DESY News: IceCube neutrino observatory at the South Pole is being expanded. Retrieved July 17, 2019 .
  2. ^ NSF mid-scale award sets off the first extension of IceCube. Retrieved July 18, 2019 .
  3. ↑ a b https://icecube.wisc.edu/~kitamura/NK/PMT/031112%20R7081-02%20data%20sheet.pdf data sheet of the R7081-02 PMT from Hamamatsu
  4. ↑ Rickard Ström: IceCube Explained. ( Memento of the original from January 17, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Department of Physics and Astronomy, Uppsala Universitet, December 13, 2011, accessed June 30, 2013. @1@ 2Template: Webachiv / IABot / www.physics.uu.se
  5. ↑ IceCube Collaboration First Observation of PeV-Energy Neutrinos with IceCube
  6. ↑ IceCube collaboration: Evidence for High-Energy Extraterrestrial Neutrinos at the IceCube Detector Science Publication of November 22, 2013
  7. ↑ IceCube collaboration "IceCube awarded the 2013 Breakthrough of the Year"
  8. ↑ IceCube Collaboration (MG Aartsen et al.): Evidence for High-Energy Extraterrestrial Neutrinos at the IceCube Detector, Science, Volume 342, 2013, Issue 6161, 1242856, abstract
  9. ↑ IceCube report on the science article
  10. ↑ IceCube sees highest-energy neutrino ever found , Symmetry Magazine, April 8, 2015
  11. ↑ Event view of highest energy neutrino detected by IceCube, Cern Courier, September 25, 2016
  12. ↑ M. Kadler et al. a., Coincidence of a high-fluence blazar outburst with a PeV-energy neutrino event, Nature Physics, Volume 12, 2016, pp. 807-814. Crime scene South Pole: suspicious blazar in the case of "neutrino" determined, University of Würzburg  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Toter Link / www.uni-wuerzburg.de  
  13. ↑ Martin Holland: Source of high-energy neutrinos localized for the first time , heise online, July 12, 2018

Coordinates: 89 ° 59 ′ 24 ″  S , 63 ° 27 ′ 11 ″  W.