Simulation of Ion Irradiation Uniformity for Large-scale Ion Track Membrane

Heavy ion irradiation has a wide range of applications in many fields such as semiconductor, medical, materials and biological, etc., and the uniformity of irradiation is the key index for many related applications, such as ion track membranes, whose uniformity of microporous distribution is directly determined by the uniformity of irradiation. Ion track membranes have excellent characteristics such as uniform pore size, controllable pore density and straight pore channels, which have good application prospects. At present, equipment for rapid production of large-area ion track membranes, such as the High Flux Irradiation Terminal of the Heavy Ion Research Facility in Lanzhou (HIRFL-TR3), has already been constructed, which realizes high-efficiency continuous production through continuous transmission of wide-area films and simultaneous heavy-ion irradiation. With the limit of magnetic scanning capability, guaranteeing the uniformity of ion irradiation for wide, continuously moving films has become an urgent research issue. In this paper, a simulation program based on path integral is developed to simulate the ion fluence distribution in ion track membrane. The results show that the higher the scanning frequency, the smaller the scanning amplitude and the better the beam spot symmetry, the more uniform the irradiation results. For irradiation on membrane whose transmission is at constat velocity, such as using two-dimensional magnetic scanning perpendicular to the direction of the beam current, there will exist a series of discrete coupling velocities to make the irradiation results uniform, and deviation from the coupling velocities may lead to periodic ups and downs in the ion fluence distribution. For the case where the beam spot shape is not ideal and the beam intensity is unstable, selecting a lower coupling speed and a specific scan frequency combination can effectively improve the uniformity; when the ion fluence deviation tolerance and the beam intensity are determined, the formula provided in this paper can be used to calculate the transmission speed required for the irradiation and to determine whether one-dimensional scanning or two-dimensional scanning is more applicable. In this study, the problem of uniformity of heavy ion irradiation has been investigated theoretically, and the results can provide a reference for related research and for ion track membrane production.