Experiment 10 - Absorption of Beta and Gamma Rays

# Experiment 10 - Absorption of Beta and Gamma Rays - Eric...

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Eric Chong PHYS C1493 Partner: Albert Lee Lab Date: December 7, 2006 Experiment 10: Absorption of Beta and Gamma Rays Introduction In this experiment, we will be observing the behavior of beta and gamma rays going through the specific metals aluminum and lead arranged in sheets to observe their behavior as a function of the amount of metal inhibiting its travel. . We use a Geiger counter apparatus measure the range of beta particles, which basically means the distance these particles can pass through a certain thickness of aluminum metal. After gauging the value for the range, we will be calculating the absorption coefficient in metallic lead using gamma radiation from a given source. The range of beta particles is based on its source, which are the neutron in radioactive nuclei. A free neutron will last for about 15 minutes before decaying into a proton, electron, or neutrino. Because of these varying properties, there is a wide range of possible energy levels that emerge from the particle after charged particles travel through the aluminum. Electrostatic impulses are from these particles will ionize atoms from nearby electrons, and this ionization causes an incident particle to consequently lose kinetic energy to eventually come to rest. The path the particle takes from initiation to this rest point is what is considered its range . The absorption of gamma rays is different in the sense that gamma rays are composed of high-energy electromagnetic radiation. Since gamma rays are inherently neutral, they do not ionize like electrons do, which is why they behave in the following three ways: Compton scattering, the photoelectric effect, or pair production. The probability that a gamma particle will react with the material is the summation of the probabilities of each individual process. Using a linearization of count rates vs. thickness of lead, we will be able to calculate the absorption coefficient. Procedure We are first required to set up the counter. The Geiger counter is developed and works in a way such that it uses high-energy particles that ionize as they move through matter. Ionization in the Geiger cathode tubing causes a violent electrical discharge, accelerating another ion, causing a chain reaction often called an avalanche charge. This process is named the Townsend avalanche, which is kept running when there is a sufficient voltage sustained. We can estimate the beta particle range by finding the point of

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## This note was uploaded on 12/16/2010 for the course PHYS 1493 taught by Professor Lab during the Spring '08 term at Columbia.

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Experiment 10 - Absorption of Beta and Gamma Rays - Eric...

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