Study on ion irradiation response of Gafchromic films for the intensity distribution measurement of a large-area beam

Yuri, Yosuke; Ishizaka, Tomohisa; Yuyama, Takahiro; Ishibori, Ikuo; Okumura, Susumu

Precise evaluation of the transverse intensity distribution of a large-area ion beam with various ion species at the AVF cyclotron is required for materials and biological researches at JAEA/Takasaki. The response characteristics of radiochromic films, Gafchromic HD-810 and EBT2, were, therefore, investigated using proton and several heavy-ion beams for developing a measurement technique of the transverse beam intensity distribution. The optical density of the films, read by general-purpose flat-bed scanners, increased linearly with the particle fluence of the beam in a low-fluence region. The linear-response range of the fluence was strongly dependent on ion species. The sensitivity of the film in terms of absorbed-dose response decreased for heavy-ion beams. The practical fluence range of the Gafchromic film for an ion beam of arbitrary energy was determined from the measurement result. Using the two types of Gafchromic films, we measured the relative intensity distribution and evaluated the size and uniformity of a large-area ion beam focused with multipole magnets. It was demonstrated that the present technique was useful for the measurement and evaluation of the ion-beam intensity distribution.