Upgrade of the Graphitization System for 14C AMS Analyses
Abstract: For decades, accelerator mass spectrometry (AMS) has been used for radiocarbon dating. The background of this technique is outlined along with an in-depth look at the graphitization process used to prepare samples for AMS analysis. The technology necessary to achieve the vacuum quality needed in graphitization and accelerator mass spectrometry is discussed as well. The graphitization system belonging to the division of nuclear physics at Lund University is modernized and tested, and four different kinds of standard samples are graphitized and analysed using the Lund Single-Stage Accelerator Mass Spectrometer. The results deviate to some extent from the expected values, and the most likely reason is that the cracker used to crack open sealed quartz tubes is faulty. Leaks of air into the system would explain the deviations, and while the rest of the graphitization system has undergone extensive leak detection, no tests have been performed to determine whether the cracker lets air into the system upon cracking a tube or begins to do so as a result of the cracking. The upgrade is deemed successful, however, as the reactors replacing the former ones have passed the extensive leak detection and the pressure transducers have proven themselves to function as expected. A calculation of the maximal conductance and throughput of the Fysicum graphitization system are performed as well, with the former being found to be 1.45∙10^-3 m^3/s and the latter being approximately 169 W.
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