1. Cosmic Ray Showers Cosmic ray activity Figure 3:
Simulation of a proton hitting the atmosphere about 20km above the ground. The cosmic shower is superimposed on a scale map of Chicago's lakefront. Electrons & positrons are green, muons are red, and gamma rays are yellow.
Figure 2:
Cosmic ray air shower with telescope
ground detection
Since the 20th century, scientists have been fascinated by the phenomena of excess radiation in the environment, other than by the known sources of natural background radioactivity. Scientists have found that cosmic rays bombard the Earth, at different rates, dependent upon their energy. Cosmic rays surround us. They make up about half of the natural background radiation of our planet. These rays are ionized atoms that originate from space. Traveling very close to the speed of light, they are produced by a number of different sources such as the sun, other stars, black holes, neutron stars, supernovas and their remnants. Our focus is to design and construct a scintillator detector. This device will count the particles passing by, by showing light and emitting sound. It will be made from a type of plastic called, scintillator. When fast moving, charged particles, such as cosmic rays pass through the scintillator, they excite the atoms in the plastic by giving them some energy. The cosmic ray slows down, and the excited atoms then lose this energy by emitting some photons of light. This light is detected by a piece of equipment called a photomultiplier. The photomultiplier multiplies the small flash of light into a large electrical signal that can be measured. The size of the electrical signal determines how many particles passed through the scintillator. Both the scintillator and photomultiplier are housed in a dark box so that the only light detected is caused by cosmic rays. This spark chamber device will be portable and will be used to demonstrate to visitors to Jefferson Lab, as well as students, teachers, etc., how cosmic rays are everywhere, and how they pass through our atmosphere where they collide with molecules, and rain down millions of highly-charged particles on the Earth's surface every second.
Valerie Bicouvaris
Berkeley Middle School
Williamsburg, VA
Douglas W. Higinbotham, Ph.D.
Thomas Jefferson
National Accelerator Facility
Special Thanks to:
Douglas W. Higinbotham
Jack Segal
Lisa Surles
Dave Abbott
Jefferson Lab
Figure 4:
Cosmic ray detector
(construction in progress)
Components include: fan in fan out/ discriminator, logic unit, counter, PMT (2), and scintillator paddles,
which together, detect and count the photons
being ‘knocked off’ the scintillator
and pass through the photomultiplier tube.