The dependence of single event upset cross-section on incident angle

swift heavy ions delivered by Heavy Ion Research Facility at Lanzhou (HIRFL) were used to bombard the 32k SRAM IDT71256 at angles from 0degrees-85degrees. The multiple bit upset(MBU) ratio can reach as high as 70% when the device was tested with 15.14MeV/u Xe-136 ions or at large angles with Ar-36 ions. The angular effect of cross section is mainly due to occurrence of MBU especially at large angles. The MBU ratio is determined by the energy deposited in the whole sensitive layer and that of more than two bit upset is increased with incident angle.