Abstract
Development of fish eggs (Oryzias latipes) will be studied in a small unmanned space platform SFU (Space Flyer Unit) launched by Japan around 1993. In such experiments, to assess the microgravity effects justly, radiation effects on the fish embryos should be investigated beforehand. We irradiated the fish embryos (at the developmental stage 11 of this species) with proton beams (5.7 MeV) generated by a tandem-type Van der Graaff accelerator. The relationship between the dose delivered by protons and the percentage of hatching fry was established. The energy loss of protons after passing Mylar foil of different thickness was measured. More embryos survived when they were irradiated with protons after a thick Mylar foil. From consideration of the geometry of the fish eggs, it was supposed that embryos received proton energy at a plateau portion before the Bragg peak.
