[en] Sample-use efficiency is an important accelerator mass spectrometry (AMS) parameter. Improvements promote increased counting statistics and the potential to reduce sample size or carrier added. Casting of the pit in Cs-sputtered targets has been done to measure primary-beam focus and to asses the effects of varying this through ion source geometry modifications on sample longevity, secondary-beam current and overall efficiency. Also demonstrated is the modification of the cathode to include a sacrificial layer of material around the sample. This allowed for improved sample consumption without loss of beam current. The techniques demonstrated here can aid in the optimisation of an ion source for maximum performance AMS.