Underground Neutrino Observatory

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The Underground Neutrino Observatory ( UNO , Underground Neutrino Observatory ) was a neutrino detector in the Mont Blanc Laboratory below Mont Blanc . It is also called "the Mont-Blanc experiment" or LSD (liquid scintillator detector, Flüssigszintillatordetektor called). It observed neutrinos of astronomical and atmospheric origin. The experiment was carried out by the Istituto di Cosmogeofisica of the CNR and the Istituto di Fisica Generale of the University of Turin with the collaboration of some scientists from the Nuclear Research Institute of the Russian Academy of Sciences in Moscow . The measurements began in October 1984. A known result is the observation of neutrinos on the day of the supernova 1987A , which however does not agree with the observations of other neutrino observatories. Operations ceased in March 1999.

construction

The detector consists of 90 tons of liquid scintillator material in 72 counters of 1 m × 1.5 m × 1 m each. Three photomultipliers are assigned to each counter . Incident neutrinos can interact with protons in the detector and thus release electrons in inverse beta decay or scatter them directly on electrons and thus accelerate them. The electrons then provide scintillation signals, which are evaluated as an event if the three photomultipliers coincide .

The shielding of the experiment against cosmic radiation is mainly done by the rock of the mountain, in addition 200 tons of iron plates protect against environmental radioactivity.

Results

On February 23, 1987, the LSD detected five neutrino events with energies from 7 to 11 MeV within just 7 seconds. This massive, short-term occurrence and the energy range suggest a reference to SN1987A, but the neutrinos from this supernova were not measured in the other detectors Kamiokande , IMB and Baksan until about four and a half hours later. The Mont Blanc neutrinos must therefore come from another process or from an earlier phase of the supernova, which theory and models have not yet been able to satisfactorily clarify.

Another experiment

A detector proposed for the first time in 1999 and then since 2003 by a collaboration around Jeffrey Wilkes is said to bear the same name, Underground Neutrino Observatory , see third web link.

Web links

Individual evidence

  1. ↑ Georg Raffelt, Max Planck Institute for Physics, Munich: Supernova Neutrino Observations: What Could We Learn? ( English , PDF; 5.5 MB) June 13, 2006. Retrieved on December 12, 2009.
  2. ↑ M. Aglietta et al: On the Event Observed in the Mont Blanc Underground Neutrino Observatory during the Occurrence of Supernova 1987a . In: Europhys. Lett. . 3, No. 12, April 9, 1987, pp. 1315-1320. doi : 10.1209 / 0295-5075 / 3/12/011 .