Prompt-γ production of 220 MeV/u 12 C ions interacting with a PMMA target
Résumé
The radiation used in particle therapy treatments produces secondary particles, either neutral or charged, when interacting with the patient body. The particles that exit from the body can be used to provide a fast feedback on the treatment plans. Here we report the measurements of prompt-gamma ray fluxes produced by the interaction of a 220 MeV/u carbon ion beam at GSI, Darmstadt, with a polymethyl methacrylate (PMMA) target. The photons were detected by means of an array of LYSO crystals, allowing for a measurement of time of flight and released energy. Different angular configurations were explored, placing the prompt-gamma detector at 60 degrees, 90 degrees, and 120 degrees with respect to the primary beam direction. The prompt-gamma energy spectra have been obtained for the different angular configurations after having taken into account the detector resolution by means of an unfolding procedure tuned with a dedicated Monte Carlo simulation. The integrated fluxes (over the full 4 pi solid angle), in the 2-10 MeV prompt-gamma ray energy range, at 60 degrees, 0 degrees and 120 degrees, are measured as Phi(gamma) (60 degrees) = (6.7 +/- 1.7) x 10(-3) sr(-1), Phi(gamma) (90 degrees) = (6.3 +/- 2.1) x 10(-3) sr(-1) and Phi(gamma)(120 degrees) = (4.4 +/- 1.1) x 10(-3) sr(-1) respectively.