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Abstract: Isotopic ratios of 10Be/9Be with a background sensitivity of 2×10−14 can now be measured with the 0.6MV Tandem accelerator of PSI/ETH Zurich using BeF2 instead of BeO as sample material and injecting BeF− to suppress the boron detector count rate. A new, high-resolution gas ionization detector with a thin silicon nitride entrance window and special preamplifier design are essential in order to achieve this sensitivity. A particle transmission of 50% is possible for charge state 1+. Due to the maximum count rate that can be accepted by the detector the BeF− currents are limited to a few hundred nA. Measurements of 10Be in rainwater samples performed under these conditions at the low terminal voltage of 0.6MV with the new compact AMS system show good agreement with results using the conventional 10Be measurement setup on the 6MV facility. Thus, this type of small scale equipment can now also be applied for 10Be AMS as long as 10Be/9Be ratios are sufficiently high and measurement time is not a limiting factor. Instead, using BeO and the degrader foil technique with a silicon nitride membrane the boron count rate can also be suppressed sufficiently but the 10Be/9Be background level is limited to 10−13 by scattered 9Be and the overall transmission is less than 5%. [Copyright &y& Elsevier]

We have developed a chemical co-precipitation method for producing conductive Ag–BeO and Ag–Al2O3 aggregates for 10Be and 26Al analyses. Co-precipitation offers a rapid alternative to grinding and mixing Be and Al oxides with Ag or Cu powder, and ensures that Al and Be oxide grains produced by baking are uniformly dispersed in the conductive Ag matrix. Co-precipitated aggregates are bulkier than pure oxides and require little or no grinding, hence samples containing significantly less than 250 μg of 9Be can be manipulated and analysed, increasing the efficiency of 10Be measurements. Binding BeO with Ag reduces the chance of hazardous BeO dust escaping during sample preparation. Although ion currents from co-precipitated Ag–BeO cathodes are lower than from mixed Nb–BeO, savings in preparation time may offset longer analysis times. [Copyright &y& Elsevier]