Effective graphitization system is the key to provide good performance of an AMS laboratory for radiocarbon measurements. We have set up a graphitization system consisted with metal vacuum line together with rubber cap test tubes for preparation of sample CO2 gas. Our graphitization system works stably and graphite yields from CO2 gases mark more than 90 percent. However systematic variations were observed in terms of the length of the graphitization at the online heating systems. The problem exists when we place a sample in a tube over night, graphitization reaction slowdown as we monitor the pressure inside of the reaction apparatus. Completion of the reaction took longer than 24 hours but the graphitization was finalized completely (ie. >90% yield from CO2 gas). Combined with Quadra pole mass spectrometric (QMS) analyses, we have found the step that potentially creating the problem. Typical threshold was observed at about 5 hours when the sample placed in the test tube to produce CO2 gas, and hence if the CO2 production step is less than 2 hours graphitization can be completed within 3 hours. In our presentation we show various experiments that we conducted to solve the problems including the results from the QMS analysis.
See more of Poster Session II
See more of The 10th International Conference on Accelerator Mass Spectrometry (September 5-10, 2005)