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Investigation of exposure rate discrepancies between energy compensated Geiger Mueller tubes and pressurized ionization chambers due to muon and anti-muon cosmic particles




Gift, Matthew, author
Johnson, Thomas E., advisor
Brandl, Alexander, committee member
Fisher, Gwenith, committee member

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Energy compensated Geiger Mueller (GM) tubes and pressurized ionization chambers are two types of gas filled detectors that measure radiation dose or exposure but operate on different physical principles. Energy compensated GMs are gaining popularity because they are less expensive and more durable than pressurized ionization chambers, however, an exposure rate discrepancy may exist between the two instruments. At an elevation of about 1524m (5,000 ft), energy compensated GM tubes were observed to have nearly a 2-fold over-response to background measurements when compared to measurements performed by pressurized ionization chambers. The goal of this research is to investigate the expected exposure rate discrepancy due to muon and anti-muon cosmic particles, since they are the largest background contributor to dose at low elevations. Theoretically calculated average chord length and stopping power, as well as, Monte Carlo N-Particle 6 were used to investigate and characterize the exposure rate from muons and anti-muons. The calculated exposure rate contribution of muons and anti-muons for the background measurement of the energy compensated GM tube was negligible and is not expected to be the primary cause for the over-response. More research is needed to characterize the discrepancy.


2017 Summer.
Includes bibliographical references.

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