Ion optic calculations and installation of a modified SIMS ion source

The NRL trace element accelerator mass spectrometer facility has recently added a modified Cameca IMS 6F SIMS instrument as a high-performance ion source. It includes the Cs primary column, the sample chamber, and the secondary ion column. The NRL accelerator facility supplants the normal mass spectrometer portion of the IMS 6F instrument. To enable uncompromised injection from both the IMS 6F SIMS at 10 keV and from the existing ion source at 70 keV, a new compound Einzel lens was added inside the pressure tank of the Pelletron accelerator. The high-energy beam line was completely reconfigured to form an angle-focusing and energy-focusing mass spectrometer. These modifications will provide improved mass spectrometry performance, both for surface analysis using the new SIMS source and for radiocarbon measurements with the older multi-cathode ion source.