Further development of accelerator mass spectrometry for the measurement of 90Sr at Lawrence Livermore National Laboratory

Based on the encouraging results of our initial efforts to develop a 90Sr accelerator mass spectrometry capability, we have undertaken efforts to enhance our system. By changing some key operating parameters and constructing an optimized detector we were able to improve the discrimination of 90Sr from the isobaric interference 90Zr and reduce our instrumental background by nearly two orders of magnitude. Our current background (4 × 106 atoms, 3 mBq) is comparable to that achievable by decay counting, but is still a factor of ten higher than what is theoretically predicted based on the efficiency of our system. Therefore, future plans include implementation of a time-of-flight system to improve the rejection of 90Zr.