The neutrino telescope AMANDA at the South Pole
The AMANDA detector for high energy cosmic neutrinos has been built (1995 – 2000) deep in the glacier at the Amundsen-Scott base at the South Pole, Antarctica. The scientific goals are among others to use the neutrino particles to investigate the question about the ”dark matter” of the Universe and to search for the sources of the highest energy cosmic rays. The neutrino particles are extremely penetrating and interacts only very rarely with matter. They are expected to be produced at different processes in the Universe and the possibility to detect high energy neutrino sources will open a new window in the study of Cosmos. In order to compensate for the extremely low probability for the neutrino to interact with matter one needs very large detectors.
The AMANDA detector is sensitive to the emitted Cherenkov light from muons created by neutrino interactions deep in the ice. In detectors of this type it is necessary to have a very transparent material like clear ice in order to efficiently propagate the light. The glacier at the South Pole is 2900 metres deep and extremely transparent at large depth. The detector consists of 677 optical modules deployed in 19 holes in the glacier, made by a hot water drilling technique. The optical modules are photo multipliers contained in pressure vessels made by spherical glass. The photo multipliers are sensitive to single photons in the wavelength range from 330 nanometers (nm) to 600 nm and have a diameter of 20 cm. The signal from each photo multiplier is transmitted via a cable up to the surface and read by the on-line computers.
The hot water drilling has been performed by the American Polar Ice Core Office (PICO) with help of Swedish drillers from Swedish Polar Research Secretariat.
The AMANDA-A detector consisting of four detector strings with 80 optical modules was deployed during the season 1993/94 at the depth of 800-1000 metres. Due to remaining air bubbles in the ice it was necessary to go deeper. Ten detector strings with optical modules were deployed between 1500 and 2200 metres during the seasons 1995/96 (four strings) and 1996/97 (six strings). The quality of the ice at these depths was found to be sufficient for a neutrino detector. The deeper detector is named AMANDA-B10 and has been taking data since January 1997. During the season 1997/98 three additional strings were deployed at depth between 1200 and 2350 meters depth in order to investigate the quality of the ice above and below the B-10 detector. The final six strings were deployed 1998/99 at a radius of 100 meters around the centre of the detector. The detector with 19 strings is now called AMANDA-II.
The AMANDA project is a collaboration between Brussels Free University, Belgium; University of California, Berkeley, USA; Lawrence Berkeley National Laboratory, Berkeley, USA; Lawrence Berkeley National Laboratory, Berkeley, USA; University of California, Irvine, USA; University of Pennsylvania, USA; Kalmar University, Sweden; University of Mainz, Germany; Stockholm University, Sweden; Uppsala University, Sweden; DESY-Zeuthen, Germany; University of Wisconsin, Madison, USA and University of Wuppertal, Germany.
The work
People and scientific equipment are transported by air from Christchurch, New Zealand to the American base McMurdo and then to the Amundsen Scott station at the geographical South Pole. For the 2000/01 season (starting at the beginning of November and ending in the middle of February) only service work and same upgrades were done with the detector. A modified version of the pre amplifier produced in Stockholm was tested and was found to significantly improve the noise reduction. The electronic noise level in the control room has increased during the years as new electronics has been added. Calibration of the time constants for the optical modules was done. The trigger electronics built by the Uppsala group was serviced by the members of the Uppsala team.
The whole detector was turned on again in the middle of February 2001.
Preliminary results
The AMANDA detector has been taking data continuously during the ”winter season” March to the end of October since 1996. During the summer months November-February we have either been adding new strings or calibrating and upgrading the electronics for the detector. In the future we expect to be able to run continuously through the whole year with only a few interruptions. A first observation of neutrinos by the AMANDA detector has been published.
About 200 neutrino candidates have now been selected from the data taken during 1997 using the 10 string AMANDA-B10 detector. These are compatible with the expected rate of neutrinos coming from cosmic ray interactions in the atmosphere. A general paper about the principles and
first results was published in Nature 2001. A paper about searching for Supernova neutrinos has been accepted for publication. In addition several analyses using the 1997 data are now almost finished and will be sent for publication soon. The analyses of the data taken during 1998,1999 and 2000 are now in progress and the different subjects are reflected in the contributions (10) to the ICRC conference in August 2001. The completed 19 string AMANDA-II detector is a much more efficient detector and easier to work with than the very narrow AMANDA-B10. We are now observing about 5 very good neutrino candidates per day.
The AMANDA detector is the leading detector in the world for high energy neutrinos. Due to the success of AMANDA the collaboration has submitted a proposal for a new larger neutrino telescope, ICECUBE, to be built close to the AMANDA site. The detector will have 80 strings and cover a volume of about l km3. The decision will be taken during 2002 and if approved the first strings will be deployed in 2004/05.
Dates
5 November 2000–31 January 2001
Participants
Principal investigator
Per Olof Hulth
Department of Physics, SCFAB, Stockholm University
Sweden
Jan Condrad
Department of Radiation Sciences, Uppsala University
Sweden
Patrik Ekström
Department of Physics, SCFAB, Stockholm University
Sweden
Pawel Marciniewski
Department of Radiation Sciences, Uppsala University
Sweden
Yulia Minaeva
Department of Physics, SCFAB, Stockholm University
Sweden
References
Ahrens, J., et al. (submitted) Search for Supernova Neutrino-Bursts with the Amanda Detector. Astroparticle Physics.
Ahrens, J., et al. 2001. Observation of High Energy Atmospheric Neutrinos with AMANDA, Ref.: C. H. Wiehusch for the AMANDA Collaboration. Proceedings of the 27th International Cosmic Ray Conference. Germany: Hamburg, 7-15 August 2001.
Ahrens, J., et al. 2001. Search for Cascade-like Events in the AMANDA-B10 Detector, Ref.: I. Taboada and M. Kowalski for the AMANDA Collaboration. Proceedings of the 27th International Cosmic Ray Conference. Germany: Hamburg, 7-15 August 2001.
Ahrens, J., et al. 2001. Supernova Neutrino-Burst Search with the AMANDA Detector, Ref.: T. Neunhöffer for the AMANDA Collaboration. Proceedings of the 27th International Cosmic Ray Conference. Germany: Hamburg, 7-15 August 2001.
Ahrens, J., et al. 2001. The AMANDA Search for High Energy Neutrinos from Gamma-Ray Bursts. Ref.: R. Hardtke and G. Barouch for the AMANDA Collaboration. Proceedings of the 27th International Cosmic Ray Conference. Germany: Hamburg, 7-15 August 2001.
Ahrens, J., et al. 2001. The Performance of the Amanda-II 19 String Array. Ref.: R. Wischnewski for the AMANDA Collaboration. Proceedings of the 27th International Cosmic Ray Conference. Germany: Hamburg, 7-15 August 2001.
Ahrens, J., et al. 2001. Search for UHE Neutrinos in AMANDA. Ref.: S. Hundertmark for the AMANDA Collaboration. Proceedings of the 27th International Cosmic Ray Conference. Germany: Hamburg, 7-15 August 2001.
Ahrens, J., et al. 2001. Time Calibration of the AMANDA Neutrino Telescope with Cosmic Ray Muons. Ref.: D. Cowen and K Hanson for the AMANDA Collaboration. Proceedings of the 27th International Cosmic Ray Conference. Germany: Hamburg, 7-15 August 2001.
Ahrens, J., et al. 2001. Scientific Potential of the AMANDA-II High Energy Neutrino Detector. Ref.: S. W. Barwick for the AMANDA Collaboration. Proceedings of the 27th International Cosmic Ray Conference. Germany: Hamburg, 7-15 August 2001.
Ahrens, J., et al. 2001. Search for Relativistic Magnetic Monopoles with the Amanda Neutrino Telescope. Ref.: P. Niessen for the AMANDA Collaboration. Proceedings of the 27th international Cosmic Ray Conference. Germany: Hamburg, 7-15 August 2001.
Ahrens, J., et al. 2001. Search for Diffuse Flux from Sources of High Energy Neutrinos with AMANDA-B10. Ref.: G. Hill for the AMANDA Collaboration. Proceedings of the 27th International Cosmic Ray Conference. Germany: Hamburg, 7-15 August 2001.
Andrés, E., et al. 2000. The AMANDA Neutrino Telescope: Principle of Operation and First Results. Astroparticle Physics 13.
Andrés, E., et al. 2001. Observation of High-Energy Neutrinos Using Cerenkov Detectors Embedded Deep in Antarctic Ice. Nature 410, 441-443.
Askebjer, P., et al. 1995. Optical Properties of the South Pole Ice at Depths Between 0.8 and l km, AMANDA Collaboration. Science 267, 1147.
Askebjer, P., et al. 1997. Optical Properties of Deep Ice at the South Pole: Absorption, AMANDA collaboration. Applied Optics 36, 4181.