Earth and environmental sciences by accelerator mass spectrometry (AMS) with the large tandem accelerator

A multi-nuclide AMS system on the 12UD Pelletron tandem accelerator at the University of Tsukuba (Tsukuba AMS system) has been able to measure environmental levels of long lived radioisotopes of 14C, 26Al, 36Cl and 129I by employing a molecular pilot beam method. In addition, we have been developing 32Si and 41Ca AMS systems for future research programs. Recently, the performance of 36Cl AMS was improved in AMS technique. The standard deviation is within ±2%, and the background is better than 5 x 10-15 for the 36Cl/Cl ratio. At present, our Tsukuba AMS research group has focused its activities especially on the measurement of 36Cl. We have measured more than 500 samples in year including earth and environmental sciences with the Tsukuba AMS system. A detailed description of the Tsukuba AMS system is given and earth and environmental applications are also described briefly. (author)