Relationship between Homogeneity of Irradiation Field and Ion Fluence at Irradiation Terminal of HIRFL

Using 55 MeV/u40Ar and 80 MeV/u20Ne ion beams delivered by the Heavy Ion Research Facility at Lanzhou (HIRFL), the relationships between the irradiation homogeneities in irradiation fields generated by the beam scanning device located at the irradiation terminal of the HIRFL and ion fluence were measured respectively with 100 μm polycarbonate films by means of nuclear track detection. The results show that the homogeneity increases when the ion fluence are lower than 1×106 and 2×107  ions/cm2, and the homogeneity has a gradual increase at the fluence of 1×106-1×107 and 2×107-1×108   ions/cm2 and then reached about 58% and 61% when the fluence are higher than 1×107 and 1×108 ions/cm2, respectively, for the40Ar and20Ne ion beams. It is evident that the homogeneity in the irradiation field made by the beam scanning device presently cannot satisfy the requirements of researches such as heavyion induced biological effects, etc. Therefore, the performance of the scanning device should be improved further.