Measurement of 10Be in air filters using BeF− ions from BaBeF4

Abstract AMS 10 Be measurements in air filter samples have been carried out using targets of BaBeF 4 and by injecting BeF − ions. As there is little interference from 10 B due to the instability of BF − , it was possible to directly count 10 Be 2+ ions at 2 MV tandem voltage for the measurements. Due to the undesirable hydroscopic nature of BeF 2 targets, we describe the preparation procedure for BaBeF 4 as an alternate final compound, which was found to have 100% efficiency for precipitating beryllium. The low (⩽10 nA) BeF − current from the IsoTrace 834 SIMS type source was adequate for measuring 10 Be in these air filters, which were exposed to 18,000 m 3 air during the sampling process. The direct measurement of 7 Be and possibly 10 Be from the same sample preparation, appears to be quite feasible using BeF 3 - ions. The production efficiency for BeF 3 - from BaBeF 4 is 5–10 times that of BeF − and is closer to that of BeO − from BeO targets. A potential beryllium carrier-free sample preparation method of producing BeF 2 by co-precipitation with a fixed quantity of CaF 2 , is also discussed.