Reprocessing of 10B-contaminated 10Be AMS targets

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS

卷:294

Article; Proceedings Paper

Simon, K. J.¹  Pedro, J. B.^2,3  Smith, A. M.¹  Child, D. P.¹  Fink, D.¹ 

[1] Australian Nucl Sci & Technol Org, Kirrawee, NSW 2232, Australia

[2] Inst Marine & Antarctic Studies, Hobart, Tas 7001, Australia

[3] Antarctic Climate & Ecosyst Cooperat Res Ctr, Hobart, Tas 7001, Australia

关键词: Beryllium-10;    Be-10;    Be-10;    B-10;    B-10;    Boron-10;    Boron;    Sample preparation;    Reprocess;    Contamination;    Accelerator mass spectrometry;    AMS;   

DOI  :  10.1016/j.nimb.2012.07.013

来源: Elsevier

【 摘 要 】

Be-10 accelerator mass spectrometry (AMS) is an increasingly important tool in studies ranging from exposure age dating and palaeo-geomagnetism to the impact of solar variability on the Earth's climate. High levels of boron in BeO AMS targets can adversely impact the quality of Be-10 measurements through interference from the isobar B-10. Numerous methods in chemical sample preparation and AMS measurement have been employed in order to reduce the impact of excessive boron rates. We present details of a method developed to chemically reprocess a set of forty boron-contaminated BeO targets derived from modern Antarctic ice. Previously, the excessive boron levels in these samples, as measured in an argon-filled absorber cell preceding the ionisation detector, had precluded routine AMS measurement. The procedure involved removing the BeO + Nb mixture from the target holders and dissolving the BeO in hot concentrated H2SO4. The solution was then heated with HF to remove the boron as volatile BF3 before re-precipitating as Be(OH)(2) and calcining to BeO. This was again mixed with niobium and pressed into fresh target holders. Following reprocessing, the samples gave boron rates reduced by 10-100x, which were sufficiently low and similar to previous successful batches of ice core, snow and associated blank samples, thus allowing a successful Be-10 measurement in the absence of any boron correction. Overall recovery of the BeO for this process averaged 40%. Extensive testing of relevant processing equipment and reagents failed to determine the source of the boron. As a precautionary measure, a similar H2SO4 + HF step has been subsequently added to the standard ice processing method. Crown Copyright (c) 2012 Published by Elsevier B.V. All rights reserved.

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