Self-ion implantation using a 62Ni isotopic beam obtained with isotopic separation accomplished in a 3 MV NEC tandem accelerator

Abstract

Self-ion irradiation has been widely used to simulate neutron damage. One issue of self-ion irradiations is the accuracy of predicted implant profiles and the associated local displacement damage. Experimental validation of ion penetration depth requires ion implantation of isotopes that are significantly low in natural abundance. Such isotopic beams are often obtained using expensive isotope-pure sputtering cathode materials. A pure Ni-62 beam can be produced from natural nickel, but effective separation requires a 90-degree bending magnet. This study demonstrates that an isotopically pure beam can be obtained using natural cathode materials with traditional small angle bending magnets. The key is to use a beam collector after the acceleration tank for mass scanning, with additional separation resolution gained from the long distance between the low-energy magnet and the beam collector. We demonstrate the feasibility of obtaining distinct peaks of Ni-58, Ni-60, Ni-61, and Ni-62 from a natural Ni cathode. Depth profiles for 2 MeV and 3.5 MeV Ni-62 ions were obtained, and show dramatic differences compared to SRIM predictions, which overestimate the ion range by ∼100% for 2 MeV and ∼30% for 3.5 MeV ions.