INFLUENCE OF PHOTON-BEAM APERTURE ON COMPTON LINE-PROFILES

A procedure to correct Compton profiles for geometrical effects, relat ed to the solid angles subtended for an X-ray source and detector, has been obtained. The geometrical response function for a given experime ntal set up is found by a Monte Carlo simulation program and is meant to be used as a histogram for convolution purposes. The main features of this function show that it is not peaked at the angle between colli mator axes because the maximum is shifted towards greater values and a lso increasingly broadens as this angle decreases. This procedure corr ects the profile shape as a whole, not only its width as was done in p revious methods. We have tested this correction with data taken from a n experiment in which 60 keV photons from a Am-241 radioactive source were scattered in a triple-distilled water sample and detected with an intrinsic germanium detector. A Compton profile, measured at an angle of 135 degrees, was compared with a tabulated one convoluted with the distribution function, and thus the result of the correction is clear ly seen.