An experimental study of the range values of monoenergetic electrons in the region 0.25 - 0.75 MeV in metallic absorbers.
thesisposted on 19.11.2015, 09:18 by Terrence Anthony. Burdett
Extrapolated range values for homogeneous electron beams derived from an electrostatic generator, over the energy range 0.25 - 0.75 MeV, have been measured in aluminium, and four other metals, covering the range of atomic number 4-79, by two methods. Current collection range values in aluminium appear significantly lower than values obtained with other detectors, such as geiger counters and ionisation chambers with good geometry, but the extrapolation of ionisation-in-depth curves in aluminium yields range values in good agreement with accepted figures. Universal transmission curves and extrapolated range-energy curves for Be, Al, Cu, Ag and Au by current collection, and universal curves for Al and Ag from ionisation-in-depth curves are presented. The former curves are taken in carefully standardised geometrical conditions, the effect of suppressing low energy secondary emission and of varying collector geometry on range values having been assessed. The previous work on extrapolated range values in metals is reviewed, and the region of applicability of the extrapolation procedure appears to be greater with current collection methods than had been assumed in previous work with other detectors. Comparison of ionisation-in-depth curves with theoretical energy dissipation distributions for equivalent plane geometries has been made, and good agreement found. By comparing the data obtained with other results in equivalent geometrical conditions, an attempt has been made to assess an inferred slight dependence of range values upon the nature of the detector.