engleski

A new graphite preparation line for AMS 14C dating in the Zagreb Radiocarbon Laboratory

In the Zagreb Radiocarbon Laboratory radiocarbon dating has been performed by a gas proportional counting and a liquid scintillation counting techniques. Recently, we implemented a graphite target production for 14C measurement by accelerator mass spectrometry (AMS). The graphite preparation rig was constructed with the help of Scottish Universities Environmental Research Centre (SUERC) Radiocarbon Laboratory within the EU FP6 project AMS-14C and the IAEA project CRO/8/006. Pre-treated organic samples (AAA method) are combusted to CO2 at 850°C over night in pre-combusted, evacuated and sealed quartz tubes in presence of CuO and Ag. The amount of CO2 corresponding to 1.5 mg of carbon is transferred from the cracked tube to the reduction line. Graphite is obtained by the reduction of CO2 with zink and iron as catalyst at 450°C. During the reduction reaction, pressure is monitored on PC and the reduction yield is calculated. The graphitization line consists of 4 units for simultaneous preparation of 4 samples. The graphite targets were measured at the SUERC Accelerator Facilities. The operation of the rig was tested by preparation of graphite from samples of known 14C activities. The graphitization yield was high (>95%) for all 4 graphitisation units. The borehole gas (CO2) activities were within the background range normally measured at SUERC, showing that our graphitization rig can satisfactory produce background samples. Here we present the first results of about 100 graphite samples prepared on a new graphitization line (and measured at SUERC): various background samples (anthracite, marble, borehole CO2), standard activity samples, and samples from the VIRI intercomparison. Use of several radiocarbon measurement techniques in our Laboratory initiated a need for development of a new relational database ZAGRADA (Zagreb Radiocarbon Database) since the existing software package could not support parallel processing of several techniques. Some characteristics of the new database will be presented.

14C dating; AMS; database

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