At the present time, for a 1 milligram sample of graphite, this limiting age is about ten half-lives, or 60,000 years, if set only by the sample size.
However, limiting ages or "backgrounds" are also determined by process blanks which correspond to the method used to extract the carbon from the sample.
The surface of the graphite is sputtered with heated, ionized cesium and the ions produced are extracted and accelerated in the AMS system.
After acceleration and removal of electrons, the emerging positive ions are magnetically separated by mass and the C counts per second are collected.
His research interests revolve around archaeological dating using AMS, including colonisation and settlement in the Pacific Islands, the application of Bayesian calibration methods to archaeological dating, sample pre-treatment chemistry and dating novel sample types.