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C

Cherenkov Radiation

    Cherenkov radiation is produced if an ionizing particle moves through a transparent medium with a velocity which is larger than the velocity of light in this medium. The atoms along the path of the particle will be polarized and emit light. The blue light in the water basin of a nuclear reactor is Cherenkov light produced by electrons of the neutron decay. More details are in the corresponding Wikipedia article.

    In astroparticle physics experiments the Cherenkov effect is used in the media:
    air: the gamma telescopes H.E.S.S, MAGIC, Veritas, CTA,
    water: the neutrino experiments Super-Kamiokande, Baikal, ANTARES, KM3NeT and the water tanks of the cosmic particle experiments AUGER and HAWK
    ice: the muon detectors of IceTop and the neutrino observatory IceCube at the South Pole.

    The Kamiokannen experiment uses water as medium to detect cosmic particles with help of the Cherenkov effect. Thermos cans are used which have inside a reflecting surface to minimize the loss of Cherenkov light.

    Coincidence

      Coincidence means that two or more electronics signals have to appear at the same time.
      The invention of the coincidence circuit, honored by the Noble Prize for physics, was the basis of many important discoveries. For particle and astroparticle experiments the coincidence method is the essential element to reduce data and to select special events.
      The DAQ card used in the students experiments allows to define different coincidence conditions.
      A detailed description of the coincidence circuit gives the Wikipedia article.