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Instrument: MUON COSMIC RAY DETECTORS
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Description
Muon Particle ? Myon

Electrically charged instable elementary particle with a rest
energy of 105.658 MeV corresponding to 206.786 times the rest
energy of an electron (0.511 MeV). The muon has an average
half-life of 2.2 ? 10-6 s. The muon belongs to the elementary
particle group of the leptons.

Most cosmic rays are protons, which are abundant in the
universe. Primary cosmic rays are particles (ionized atoms)
such as a single proton (nuclei of hydrogen; about 90% of all
cosmic rays) up to an iron nucleus and beyond, but being
typically protons and alpha particles (identical to helium
nuclei; majority of the remaining 10%) traveling through the
interstellar medium. Most of these originate outside of our
solar system (i.e. from Supernovae), but some of them come from
sun.

When these primary cosmic rays hit Earth's atmosphere at around
30,000m above the surface, the impacts cause nuclear reactions,
which produce pions. These pions decay into a muon and muon
neutrino (= antineutrino) at about 9000 m altitude, which rain
down upon the surface of the earth, traveling at about
0.998c. Many muons decay on the way down into Neutrinos and an
electron while others reach the surface, but there are still
enough to be detected fairly easy. Actually, about 200 rain down
on each square meter of Earth every second.

We detect the muons by utilizing a homebrew Geiger-M?ller
detector. The Geiger counters are supplied by high voltage,
which creates a very high electric field near the anode of the
detectors. When a cosmic particle enters one detector, it strips
off some electrons of some atoms. These electrons move towards
the positively charged wires, are accelerated by the huge
electric field and have enough energy to strip more electrons
from other gas molecules. These electrons are accelerated too in
order to strip more and more electrons. This electric avalanche
consisting of more than a billion negative charges rains down on
the positively charged wire, causing a current that flows into
the simple detection circuit.

Since other particles are stimulating the detector aswell, we
will use 2 detectors to avoid false detection. Other particles
originating from i.e. terrestrial radiation will also cause a
stimulation, but those particles have too less energy to
penetrate both detectors. They will end up either in the first
detector or shortly after it. So we simply have to look for
almost instant detections in both detectors and consider this as
successful detection.

Additional information available at
http://muon.captain.at/