EXPERIMENTAL STUDIES AND NUCLEAR-MODEL CALCULATIONS ON THE FORMATION OF RADIOACTIVE PRODUCTS IN INTERACTIONS OF MEDIUM-ENERGY PROTONS WITH COPPER, ZINC AND BRASS - ESTIMATION OF COLLIMATOR ACTIVATION IN PROTONTHERAPY FACILITIES

Excitation functions of (p,x) processes on collimator materials for ra diation therapy (Cu, Zn and brass), leading to the formation of long-l ived activation products, were measured over the proton energy range 7 0 to 350 MeV using the stacked-foil technique. In most of the cases th e product activity could be measured non-destructively via gamma-ray s pectrometry; for studies on low-yield products, however, radiochemical separations were essential. A comparison of the data obtained via an integration of the differential data for Cu and Zn with integral cross -section measurements on brass showed an agreement within +/- 17%. The experimental data for Cu-nat, Zn-nat and brass were also compared wit h theoretical data obtained using the modified hybrid nuclear model co de ALICE-IPPE (1996) for intermediate energies. The agreement was foun d to be good up to about 120 MeV. For products rather away from the ta rget elements, large deviations were observed. Using the measured data , an estimation of collimator activation in proton therapy facilities was done. (C) 1997 Elsevier Science Ltd. All rights reserved.