A new capability for ANTARES: 7Be by AMS for ice samples

Abstract ANSTO, in collaboration with the Australian Antarctic Division (AAD) and the Antarctic Climate and Ecosystems Cooperative Research Centre (ACE CRC), has an on-going program of 10 Be ( t ½  = 1.39 × 10 6  a) concentration measurement in firn and ice at Law Dome, Antarctica. In recent years snow pit samples have also been measured for 7 Be ( t ½  = 53.28 d) concentration as this isotope has the potential to give further insight into the transport and deposition of cosmogenic beryllium to Law Dome and so improve the use of 10 Be as a proxy for solar activity. Early 7 Be measurements were made by gamma-ray spectrometry (GRS) with typical counting times of 3 days. In 2010, we developed the capability for 7 Be/ 9 Be measurement on the 10 MV ANTARES (Australian National Tandem Accelerator for Applied Research) accelerator using carbon foil post-stripping of 7 Be 3+ to 7 Be 4+ to eliminate the 7 Li isobar. We describe the method and explain the advantages of using accelerator mass spectrometry (AMS) over GRS for 7 Be analysis.