Use of Gafchromic films to measure the transverse intensity distribution of a large-area ion beam

Yuri, Yosuke; Ishizaka, Tomohisa; Yuyama, Takahiro; Ishibori, Ikuo; Okumura, Susumu; Kitamura, Akane; Yamaki, Tetsuya; Sawada, Shinichi

In the TIARA cyclotron, it is required that transversely uniform ion beam formation by multipole magnets should be evaluated with the uniformity performance precisely. One of techniques developed for it is to measure the distribution of the beam intensity handily using Gafchromic radiochromic films. In order to obtain fluence ranges available, ion-beam irradiation experiments for the film calibration were performed for several ion species. The fluence range where the optical density increased linearly was overlapped with that required for irradiation in materials and biological research. Thus, the relative transverse intensity distribution could be measured with the films practically. Another technique using a polymer film with track-etched pores was tried to compare to the Gafchromic film measurement. The relative beam uniformity determined by the Gafchromic film method agreed with the relative standard deviation of the microscopic pore densities determined by the track-etching technique.