Heavy-ion beam irradiation facility for biological samples in RIKEN

Biological samples are irradiated with heavy-ion beams at a heavy-ion beam irradiation facility in RIKEN to perform mutation breeding. The energies of the heavy-ion beams are sufficiently high to irradiate biological samples of macroscopic thickness in air. A uniform dose distribution is a key to a systematic study of the effect of the heavy-ion beams, and thus to the improvement of mutation efficiency. We selected a sufficiently high beam energy to avoid the Bragg peak to realize a uniform dose distribution along the beam path. The outline of the beam line is presented. The linear energy transfers (LETs) of the heavy-ion beams are selected using a range shifter and an energy adjuster to investigate the LET dependence of the irradiation effect. More than five hundred samples are automatically sent to the beam position using an automatic sample changer, which put the heavy-ion beam induced mutation breeding to practical use. The structure and function of the automatic irradiation system are also presented.