AixMICADAS, the accelerator mass spectrometer dedicated to 14C recently installed in Aix-en-Provence, France
AixMICADAS, the accelerator mass spectrometer dedicated to 14C recently installed in Aix-en-Provence, France
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DOI：
10.1016/j.nimb.2015.01.075
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发表时间：
2015-10-15
影响因子：
1.3
通讯作者：
Synal, Hans-Arno
中科院分区：
文献类型：
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作者：
Bard, Edouard;Tuna, Thibaut;Synal, Hans-Arno
2014年3月底，在普罗旺斯艾克斯的CEREGE安装了专门用于测量超小样品中的C-14的紧凑型AMS系统，并安装了自动石墨化系统。AixMICADAS在200千伏左右运行，氦中的碳离子剥离导致大约47%的传输。混合离子源使用石墨靶和二氧化碳气体。它与一个多功能的气体接口系统相结合，确保了来自不同来源的稳定的气体测量：玻璃瓶中二氧化碳的裂解装置，用于燃烧有机物的元素分析仪，以及通过湿化学处理碳酸盐的自动化系统。在运行的前半年进行的分析表明，对约1毫克碳的现代样品的精度约为2%。对原子能机构不同年龄的C-14标准物质的测量表明，与共识值符合得很好。对地质石墨岩的直接测量表明，其机器背景相当于68000年前的时代。因此，AixMICADAS仅受野外和实验室样品的C-14污染的限制。气体离子源及其气体界面系统的性能通过两个二氧化碳生产装置进行测试：元素分析仪和自动碳酸盐水解装置。这些测试表明，在10到100微克C的范围内，根据样品质量的不同，在3到30分钟的时间跨度内可以产生10-15IAA量级的C-12(-)离子束。将自动水解系统耦合到AixMICADAS的气体离子源，使我们能够开发一种通过直接测量碳酸盐样品的浸出物和残留物的C-14来顺序浸取碳酸盐样品的方法。主要优点是，对于特定的样品，所有步骤的浸出和水解都在同一个小瓶中进行。对一个年轻的碳酸盐样品(约6600年前)进行了顺序淋洗，其C-14年龄与以前的测定结果一致，没有显示出明显表面污染的迹象。相比之下，测试还表明，从非常古老的碳酸盐中浸出的二氧化碳比残留的样本要年轻得多。这项研究虽然是初步的，但已经证实，如果我们要准确地测量这些样品的真实年龄，通过酸浸对旧碳酸盐进行预处理是必不可少的。(C)2015爱思唯尔B.V.保留所有权利。
A compact AMS system dedicated to measuring C-14 in ultra-small samples was installed at the CEREGE in Aix-en-Provence at the end of March 2014, together with an automated graphitization system. AixMICADAS operates at around 200 kV with carbon ion stripping in helium leading to a transmission of about 47%. The hybrid ion source works with graphite targets and CO2 gas. It is coupled to a versatile gas interface system that ensures stable gas measurements from different sources: a cracker for CO2 in glass ampoules, an elemental analyzer for combusting organic matter and an automated system to handle carbonate by wet chemistry.The analyses performed during the first half-year of operation show that a precision of about 2% is reached on modern samples of about 1 mg of carbon. Measurements of IAEA reference materials of various C-14 ages show a good agreement with consensus values. Direct measurements of geological graphites indicate a machine background equivalent to an age of 68,000 years BP. AixMICADAS is thus limited solely by the C-14 contamination of samples in the field and in the laboratory.The performances of the gas ion source and its gas interface system were tested with two CO2 production units: the elemental analyzer and the automated carbonate hydrolysis unit. These tests show that samples ranging between 10 and 100 mu g C can produce a C-12(-) ion beam of the order of 10-15 IAA during time spans ranging from 3 to 30 min depending on the sample mass.Coupling the automated hydrolysis system to the gas ion source of AixMICADAS, enables us to develop a method involving sequential leaching of carbonate samples with direct C-14 measurements of the leached fractions and the residual sample. The main advantage is that all of steps leaching and hydrolysis are performed in the same vial for a particular sample.A sequential leaching was applied to a young carbonate sample (ca. 6600 years BP) whose C-14 age agrees with previous determination and which shows no sign of significant surface contamination. By contrast, the tests also show that the leached CO2 from very old carbonates is significantly "younger" than the residual sample. This study, though preliminary, already confirms that pretreatment by acid leaching of old carbonates is essential if we are to accurately measure the true age of such samples. (C) 2015 Elsevier B.V. All rights reserved.