The Keck Carbon Cycle AMS laboratory, University of California, Irvine: Initial operation and a background surprise

A new radiocarbon accelerator mass spectrometry (AMS) laboratory for carbon cycle studies has been established at the University of California, Irvine. The 0.5MV AMS system was installed in mid-2002 and has operated routinely since October of that year. This paper briefly describes the spectrometer and summarizes lessons learned during the first year of operation. In the process of setting up the system, we identified and largely suppressed a previously unreported C-14 AMS background: charge exchange tails from N-14 beams derived from nitrogen-containing molecular ions produced near the entrance of the accelerator.