System of cell irradiation with a precise number of heavy ions (II)

A single cell irradiation system has been developed at JAERI-Takasaki to elucidate biological effects of low dose and low dose-rate space radiation. The system has been installed at high-energy collimated heavy-ion microbeam apparatus under a vertical beam line of AVF-cyclotron accelerator. Individual mammalian cultured cells are irradiated in the atmosphere on the cell dish, the bottom of which is made of ion-track-detector TNF-1 (modified CR-39), with a single or precise numbers of 11.5 MeV/u 40Ar13+, 13.0 MeV/u 20Ne7+, and 18.3 MeV/u 12C5+ ions. Positional data of the target cells are obtained at the off-line microscope before irradiation. Targeting and irradiation of the cells are performed automatically at the on-line microscope of the microbeam apparatus according to the obtained data. About 50-100 cells are irradiated in several minutes. The number of ions traversed the cells attached on the ion track detector were counted with a plastic scintillator-photomultiplier tube assembly and a constant fraction discriminator. Immediately after the irradiation, the bottom of the cell dish was etched at 37 degrees C to check the spatial distribution of irradiated ions. The one batch of cell sample is treated in about 1 hr including the phases of cell finding, irradiation, and etching/observing of the ion tracks.