Simple, immediate and calibration-free cyclotron proton beam energy determination using commercial targets
Sergio J.C. do Carmo a), P.M. de Oliveira a) and Francisco Alves b,c)
a) ICNAS — Produção, University of Coimbra, Pólo das Ciências da Saúde, Azinhaga de Santa Comba; 3000-548 Coimbra; Portugal b) ICNAS – Institute for Nuclear Sciences Applied to Health; University of Coimbra; Pólo das Ciências da Saúde, Azinhaga de Santa Comba; 3000-548 Coimbra; Portugal c) IPC – Instituto Politécnico de Coimbra – Coimbra Health School; 3046-854 Coimbra; Portugal
Poster
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Although an accurate knowledge of the incident beam energy is fundamental for the production of medical radioisotopes, either to optimize production yields or to prevent the co-production of undesired radioimpurities, biomedical cyclotrons are not properly equipped for beam energy measurements. This work presents an indirect method for determining the energy of the proton beam in cyclotrons, using only materials from routine productions, therefore immediately available on-site, and also requiring no additional experimental set up. The developed method based on the stack–foil technique requires no absolute efficiency calibration nor beam current measurements, avoiding thus two major sources of uncertainties, and make use of the fact that each monitor excitation function presents a unique shape so that the activity profile vs. depth, i.e. vs. foil, is specific of the monitor reaction but also dependent on the incident energy. The natTi(p,x)48V monitor reaction was chosen as it presents more pronounced variations in the energy range of interest and foils of titanium are available on site from routine productions. An energy degrader of adequate thickness, also made form available material from routine productions, was appropriately placed in the stack so that it matches the energy range for which there is almost no variation in the excitation function; concentrating thus the foils results in the preferable energy ranges. Two stacks of natural Titanium thin foils spaced by an energy degrader mounted in a commercial IBA Nirta liquid target arrangement were irradiated and the resulting activities of 48V were assessed by either HPGe spectrometer. The beam energy was determined at distinct exit ports and also using different high voltages in the radio-frequency amplifier.