ProNova Solutions LLC

230 MeV proton beam out of a cyclotron was delivered into a Zebra multilayered IC detector (IBA) calibrated in terms of penetration range in water.The analysis of the measured Bragg peak determines penetration range in waterwhich can be subsequently converted into proton beam energy using Range-Energytables. We extended this analysis to obtain an estimate of the beam energyspread out of the cyclotron. Using Monte Carlo simulations we established thecorrelation between Bragg peak shape parameters (width at 50% and 80% doselevels, distal falloff) and penetration range for a monoenergetic proton beam.Then we studied how this correlation changes when the shape of Bragg peak isdistorted by the beam focusing conditions. We found that small field size ordiverging beam cause Bragg peak deformation predominantly in the proximalregion. The distal shape of the renormalized Bragg peaks stays nearly constant.This excludes usage of Bragg peak width parameters for energy spread estimates.The measured Bragg peaks had an average distal falloff of 4.86mm, whichcorresponds to an effective range of 35.5cm for a monoenergetic beam. The32.7cm measured penetration range is 2.8cm less. Passage of a 230 MeV protonbeam through a 2.8cm thick slab of water results in a 0.56 MeV energy spread.As a final check, we confirmed agreement between shapes of the measured Braggpeak and one generated by Monte-Carlo code for proton beam with 0.56 MeV energyspread.