Glossary

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M

Multi-Pixel Photon Counter

    The Multi-Pixel Photon Counter (MPPC) is a solid-state photomultiplier which has several advantages compared to normal PMTs as small size, robustness and much lower input power (70-100 V). A disadvantage is the temperature dependence of the output signal. Therefore, long-term measurements with MPPCs should be performed at stable temperature.
    Details on MPPCs are given in the Wikipedia article. The MPPC used in the CosMO detectors has a sensitive surface of 3 mm x 3 mm and produced by Hamamatsu (product type S10362-33-50C). Details on MPPCs can be found in the technical note.

    Muon

      Muons are elementary particles, “big brothers” of electrons. They have a 208 times larger mass, are however not stable. Muons are one of the main components of the cosmic particle flux reaching the Earth’s surface. They are decay products of short living pions and kaons which are produced in cosmic particle interactions in the upper atmosphere. The average life time of muons is about 2.2 microseconds. With our students and Cosmic@Web experiments different aspects can be investigated. Of special interest is the measurement of the muon life time. The life time allows to explain and to understand the phenomena of Einstein’s special theory of relativity.
      More details about muons can be found in the Wikipedia article.