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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

      We use the term coincidence when several events occur with a small temporal or spatial distance. The invention of the coincidence circuit, awarded the Nobel Prize for Physics, was the basis for many important discoveries.

      In particle and astroparticle experiments, the coincidence method helps to minimize errors or to filter for special events. For this purpose, a causal relationship between the simultaneous occurrence of signals and the physical phenomenon to be observed must be known.

      For example, for CosMO detectors connected in coincidence, an output signal is only generated if each individual detector registers an input signal within a previously defined, small time interval. The basic assumption is that the muons of cosmic rays to be observed have sufficient energy to penetrate several detectors and each produce a signal. Since these muons move almost at the speed of light, the input signals in the detectors occur at very short time intervals. There are also many low-energy phenomena that can trigger a signal in one detector but not in several. But such events occur randomly, without any time connection. Accordingly, it is much more likely that the output signal from detectors connected in coincidence comes from a muon than from any other phenomenon.

      A coincidence condition can be set for the student experiments on the DAQ card using muonic.

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