Journal
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS
Volume 329, Issue -, Pages 22-29Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.nimb.2014.02.130
Keywords
Accelerator mass spectrometry (AMS); Volatile elements; Chlorine; Negative ion sputter sources; Long-term memory effect; Interlaboratory comparison
Categories
Funding
- DAAD/EGIDE [500 888 61, 22077QC]
- DFG [RU 1832/1-1]
- INSU/CNRS
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Understanding and minimization of contaminations in the ion source due to cross-contamination and long-term memory effect is one of the key issues for accurate accelerator mass spectrometry CAMS) measurements of volatile elements. The focus of this work is on the investigation of the long-term memory effect for the volatile element chlorine, and the minimization of this effect in the ion source of the Dresden accelerator mass spectrometry facility (DREAMS). For this purpose, one of the two original HVE ion sources at the DREAMS facility was modified, allowing the use of larger sample holders having individual target apertures. Additionally, a more open geometry was used to improve the vacuum level. To evaluate this improvement in comparison to other up-to-date ion sources, an interlaboratory comparison had been initiated. The long-term memory effect of the four Cs sputter ion sources at DREAMS (two sources: original and modified), ASTER (Accelerateur pour les Sciences de la Terre, Environnement, Risques) and VERA (Vienna Environmental Research Accelerator) had been investigated by measuring samples of natural Cl-35/Cl-37-ratio and samples highly-enriched in Cl-35 (Cl-35/Cl-37 similar to 999). Besides investigating and comparing the individual levels of long-term memory, recovery time constants could be calculated. The tests show that all four sources suffer from long-term memory, but the modified DREAMS ion source showed the lowest level of contamination. The recovery times of the four ion sources were widely spread between 61 and 1390 s, where the modified DREAMS ion source with values between 156 and 262 s showed the fastest recovery in 80% of the measurements. (C) 2014 Elsevier B.V. All rights reserved.
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