Benchmarking 10Be2+ ion detection against 10Be3+ method at ANSTO
Dr Klaus Wilcken1, Krista Simon1, Sam Micallef1
1ANSTO, Lucas Heights, Australia
It has been demonstrated that low background high efficiency measurement of 10Be can be achieved with 2+ charge state using 3 MV accelerator . The method is advantageous because transmission to 2+ charge state at 3.0 MV is roughly 60% and nearly double what is achieved with 3+ ions using 5-6 MV accelerators and Ar stripper gas. Increased measurement efficiency translates into improved precision and sensitivity.
Typically, AMS facilities measure samples from a range of satellite sample preparation laboratories. Different procedures and laboratory settings often lead into varying 10B rates from the prepared BeO targets. Therefore it is desirable that the employed AMS method can accommodate samples with varying 10B rates without negatively impacting the 10Be measurement.
To benchmark the 10Be2+ methodology against our routine 10Be3+ method, based on 6.0 MV acceleration voltage and standard passive Ar absorber cell , we evaluated the impact of increasing B concentration to the measurement background with both methods. Ion detection for 10Be2+ ions was done with standard gas ionisation detector preceded by SiN-foil stack to stop the 10B ions. To optimise the achievable background and its sensitivity to varying B-rates different accelerator voltages between 3 and 5 MV were evaluated.
 P. Steier et al. / International Journal of Mass Spectrometry 444 (2019) 116175
 K. Wilcken et al./ Nuclear Inst. and Methods in Physics Research B 455 (2019) 300–304
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