Statistical assessment of long-term performance for AMS measurements at IUAC, New Delhi

Abstract

A 500 kV ion Accelerator based Accelerator Mass Spectrometer (AMS) system was established in 2015 at the Inter-University Accelerator Centre (IUAC), New Delhi, India (14C Lab Code: IUACD) and is being used routinely for 14C, 10Be and 26Al measurements. The AMS System is backed by three automated graphitization equipment (AGE), a carbonate handling system (CHS) in graphitization laboratory and an appropriate clean laboratory for the chemical processing of samples in case of 10Be and 26Al measurements. In view of the increasing demand for 14C based studies, a major portion of the machine time goes into 14C measurements as compared to other isotopes.It is imperative to assess, monitor and establish the consistency of the performance of the AMS measurements over time since its inception. We have evaluated the short- and long-term performance of 14C measurements with the AMS set-up at IUAC, New Delhi, in terms of the reproducibility, accuracy, precision and calculation of random machine error (RME) in a routine laboratory environment using the International Atomic Energy Agency (IAEA) secondary standards (C1-C9) and chemical blanks in each session. A comparison of the analytical figures of merit between the short- & long-term usages of the AMS facility is presented through a statistical approach highlighting the importance of the measurements and evaluation of primary standards, secondary standards, blanks, and replicates in each of the experiments. A comparison of the analytical performances between the initial set-up and later adoption of a modified analytical protocol has also been made.