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内容記述 |
Optical imaging is a cost-effective technique to characterize of physical properties of heavy ion beams. However, optical imaging has not been used for radioactive carbon ion beams. Since radioactive ion beams have larger momentum spreads (i.e. energy spreads) than those of conventional stable ion beams, the physical properties should be carefully measured during quality control. Here, we propose optical imaging for quality control of radioactive 11C ion beams with different momentum spreads (i.e. energy spreads). A polymethyl methacrylate (PMMA) phantom (10.0 × 10.0 × 9.9 cm3) was irradiated by 11C ion beams (200 MeV/u) with three different momentum acceptances (M.As) of 1%, 2% and 4% corresponding to the energy spreads of 1.8, 2.9, and 5.0 MeV/u, respectively (Fig. 1(a)). We obtained luminescence and Cerenkov images using an optical imaging system during and after irradiation, which were used for estimations of the Bragg peak position and energy spread, respectively (Fig. 1(b)). The Bragg peak position was estimated by using luminescence imaging with a maximum error of 0.5 mm (Fig. 2(a)). The full width at half maximum (FWHM) of the Cerenkov signals was linearly increased with the M.A (Fig. 2(b)). The positional difference between the Bragg peak and Cerenkov peak was also increased with the M.A. In conclusion, the optical imaging technique is a cost-effective solution to characterize the physical properties of 11C ion beams for beam quality control. |
