About the detector...
This page gives a basic outline for how the Willamette Cosmic Ray Detector (CRD) works and some of the very basic principles behind cosmic radiation. For more depth check out the links section for the instruction manual.
Every day, high energy particles from outer space and the Sun collide with Earth's atmosphere. These collisions cause what are known as particle cascades, a sort of chain reaction of high energy particles decaying into lower energy particles which eventually reach us at the surface. A diagram of possible cosmic ray showers is shown at right.
What kind of particle is created depends on the energy of the primary particle and quantum mechanics. This detector deals mostly with muons, which are the most abundant portion of the spectrum.
The muon is very similar to the electron except it is about 200 times heavier. Historically it is important because it was the first particle to confirm Einstein's theory of Special Relativity. Since a muon has a very short lifetime (2.2μs), using classical physics it should not be possible to detect muons at sea level or near the Earth's surface. The presence of these particles at low elevation and even underground is explained by Lorentz contraction and time dilation, two results of special relativity.
How it works...
The CRD relies on plastic scintillation paddles to detect the presence of incoming radiation. When a muon or other particle passes through the material, the scintillator releases a corresponding photon. The paddle's covering helps reflect these photons inside the plastic until the arrive at the photomultiplier tube (PMT). The PMT then converts the photon into an electrical signal for processing by the electronics.
The onboard electronics then convert this analog pulse into a digital signal for a coincidence counter. Coincidences between the two paddles are then tallied on the LED display or an optional Texas Instruments CBL calculator interface.
For more detail on PMT's, the electronics, or other functions please check out my Senior Seminar Final Report in the downloads section. |
