A cold finger cooling system for the efficient graphitisation of microgram-sized carbon samples

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dc.contributor.authorYang, Ben_AU
dc.contributor.authorSmith, AMen_AU
dc.contributor.authorHua, Qen_AU
dc.date.accessioned2012-06-27T05:48:08Zen_AU
dc.date.available2012-06-27T05:48:08Zen_AU
dc.date.issued2011-03-24en_AU
dc.date.statistics2012-06-27en_AU
dc.description.abstractAt ANSTO we use the Bosch reaction to convert sample CO2 to graphite for production of our radiocarbon AMS targets. Key to the efficient graphitisation of ultra-small samples is the type of iron catalyst and the effective trapping of water vapour in a ‘cold finger’ during the reaction. We have developed a simple liquid nitrogen cooling system that enables us to rapidly adjust the cold finger temperature in our laser-heated ‘microfurnace’, optimised for the graphitisation of microgram-sized carbon samples. This system is used to firstly transfer the CO2 into the microfurnace, to maintain the cold finger at -80°C for ~ 5 minutes while the CO2 is converted to CO and then at -160°C for ~ 25 minutes for the remainder of the reaction as the CO is converted to graphite. It comprises a machined aluminium cylinder mounted in the insulated cap of a 600 ml Dewar. The lower end is submerged in liquid nitrogen (LN2). The upper end has a smaller diameter which is wound with an electric heating element and is provided with a thermocouple and a central hole into which the cold finger is inserted. Electrical power to the heater is adjusted by PID control, permitting the cold finger temperature to be adjusted over the range -50°C to -160°C at rates of up to 40°C/min. This simple system uses modest amounts of LN2 (typically < 0.2 L/hr during graphitisation) and is compact and reliable. We have used it to produce over 120 AMS targets containing between 5 and 20 μg of carbon, with conversion efficiencies for 5 μg targets of typically 90-100%. We are currently modifying this cooling system for use with our conventional graphitisation reactors. Copyright (c) 2011 AMS12en_AU
dc.identifier.citationYang, B., Smith, A., Hua, Q. (2011). A cold finger cooling system for the efficient graphitisation of microgramsized. Presentation to the 12th International Conference on Accelerator Mass Spectrometry (AMS 12), 20th - 25th March 2011. Museum of New Zealand: Te Papa Tongarewa, Wellington, New Zealand, (pp. 214).en_AU
dc.identifier.conferenceenddate25 March 2011en_AU
dc.identifier.conferencename12th International Conference on Accelerator Mass Spectrometry (AMS 12)en_AU
dc.identifier.conferenceplaceWellington, New Zealanden_AU
dc.identifier.conferencestartdate20 March 2011en_AU
dc.identifier.govdoc4442en_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/4374en_AU
dc.language.isoenen_AU
dc.publisher12th International Conference on Accelerator Mass Spectrometry (AMS-12)en_AU
dc.subjectCooling systemsen_AU
dc.subjectCarbonen_AU
dc.subjectGraphitizationen_AU
dc.subjectANSTOen_AU
dc.subjectAluminiumen_AU
dc.subjectReactorsen_AU
dc.subjectAcceleratorsen_AU
dc.subjectSpectroscopyen_AU
dc.subjectCoolingen_AU
dc.titleA cold finger cooling system for the efficient graphitisation of microgram-sized carbon samplesen_AU
dc.typeConference Presentationen_AU
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