DOSE DISTRIBUTION OF PROTON-BEAMS WITH NMR MEASUREMENTS OF FRICKE-AGAROSE GELS

Fricke-agarose gels have been irradiated with a proton beam, Then samp les have been extracted at different depths with respect to the beam p enetration distance, corresponding to different irradiation doses. Rel axation times T-1 and T-2, measured at 17 MHz, appear sensitive to thi s kind of radiation, In particular, T-2 exhibits three components T-2( a), T-2(p) and T-2(c), the first two being sensitive to proton irradia tion. At 1% agarose concentration, the relaxation rates R-1 = 1/T-1, R -2(a) = 1/T-2(a) and Rb-2(b) = 1/T-2(b) Of samples irradiated with bot h modulated and unmodulated beams, increase with the dose, irrespectiv e of the beam energy, The yield G of Fe3+ ions per 100 eV of absorbed energy is always higher than that obtained for gamma irradiated sample s. (C) 1997 Elsevier Science Inc.