High Energy Cosmic Rays
...and the Sun
There are two categories of cosmic rays: primary and secondary cosmic rays. Real (or "primary") cosmic rays can generally be defined as all particles that come to earth from outer space. These primary cosmic rays generally do not make it through the earth's atmosphere, and constitute only a small fraction of what we can measure using a suitable set of particle detectors at the earth's surface.
...and Supernovae
The cosmic rays we are interested in at this web site have a much higher energy than those from the sun. They typically have energies of several billion electron volts (GeV), but they can have many trillion electron volts (TeV). For the most part, they are protons, and they really do come from the "cosmos", perhaps even from outside our own galaxy. It is not precisely known how these protons get their high energy, but one possibility is that they are accelerated in very high and extensive magnetic fields surrounding, for example, the remnants of supernova explosions.
...and the Atmosphere
Cosmic rays are (mostly) protons from outer space. When a high-energy proton hits the earth's atmosphere, it will collide and interact with one of the nuclei of the atmospheric gas molecules.
SLAC's Cosmic Ray Detector
The Cosmic Ray Detector consists of three pairs of scintillator panels for muon detection. Sets A, B, and C (see below) are oriented with the flat surface of the panels horizontally, at 45°, and vertically, respectively. In each pair, the panels measure 4.875 inches (12.4 cm) wide by 8 inches (20.3 cm) long, and the distance between them is 18.5 inches (47.0 cm). The panels are shielded from light with aluminum foil, black plastic sheets, and black tape. When muons penetrate through these panels, chemicals within will scintillate (emit flashes of light).
