Imaging of fragment particles in water by nuclear spallation during carbon-ion irradiation.

Recently we found that the luminescence imaging of water during carbon-ion irradiation was possible using a cooled charge-coupled device (CCD) camera and the method could be used for range estimation of the beam. In the luminescence image, we found luminescence from the fragment particles produced by the nuclear spallation reaction of carbon ions. The luminescence may be used for the estimation of the distribution of the fragment particles by the nuclear spallation. For this purpose, we irradiated carbon ions of 241.5 MeV u-1 to a water phantom and measured the luminescence image of water using a CCD camera. Then, we carefully observed the luminescence distribution after the Bragg peak to find the luminescence from the nuclear spallation reaction. In the luminescence image, we could clearly observe the luminescence from the fragment particles produced by the nuclear spallation reaction during irradiation of carbon ions. The beam widths of the luminescence image of the nuclear spallation were compared with those measured by the ionization chamber. The relative difference of the beam width at FWHM between luminescence image and ionization chamber was 23%. With these results, we conclude that the luminescence image of water during carbon-ion irradiation has a potential to be a new and efficient method for the width estimation of the fragment particles by the nuclear spallation reaction.