Department of Physics and Astronomy: Publications and Other Research
Date of this Version
June 1995
Abstract
Low doses of radiation are frequently inferred to mean doses of the order of 10-100 mGy, regardless of the end point or the nature of the irradiation, as if the energy were deposited uniformly through all targets. Yet, the fluence in a charged particle beam at which there is an average of 1 charged particle transit per target leaves 37% of the targets untouched. At an average of 3 transits per target, 5% of the targets experience no particle transits. Only at an average of 5 transits per target do 99% of the targets achieve one or more transits. One might consider this to be the lowest meaningful fluence for 1-hit detectors. For 2-hit detectors an average of 7 transits per target are required to achieve 2 or more hits in 99% of the targets. These conclusions arise from the cumulative Poisson distribution. To translate these numbers into the lowest meaningful dose requires consideration of target size and particle LET.
Comments
Published in Health Physics 68:6 (June 1995), p. 859.