Copyright (c) James King-Holmes, 2005
The Unit has much specialised equipment for the treatment of samples for radiocarbon dating and for the measurements on the isotopes themselves. Much of this equipment has been developed at or designed by members of the unit specifically for tasks undertaken.
The main instruments of the unit are the stable isotope mass spectrometers, gas collection systems, graphitisation lines and the accelerator mass spectrometer.
The calibration and maintenance of all equipment is documented and managed through our ISO-9000 quality management system.
The unit has four stable isotope mass spectrometers. Two Europa Scientific instruments are used in conjunction with automated gas collection systems for radiocarbon samples. Another two (one from Finingan and one from Europa Scientific) that are used for stable isotope research. All are usually operated in continuous flow mode (where the sample is transported in a stream of inert He gas). They are set up to measure the carbon and nitrogen compositions and stable isotope ratios. Precisions are usually better 0.1 to 0.2 per mil for d13C and 0.3 per mil for d15N.
We have two purpose-built gas-collection systems, designed at ORAU, which semi-automate the collection of samples from continuous-flow combustion, and mix the samples with the correct quantities of hydrogen for conversion to graphite.
The next stage in the process is graphitisation. For this we again have equipment designed at ORAU which allows us to graphitise up to 40 samples at any one time.
The AMS system is a very new one (commissioned September 2002) built specially for us for radiocarbon dating by High Voltage Engineering Europa BV. The instrument is designed to give very high precision measurements on a routine basis.
On aspect of the system, a gas ion source for direct measurement on carbon dioxide samples has been a joint development project between HVEE and the Oxford laboratory. The new system gives us routine measurements at about the 0.3% level (equivalent to about 25 to 30 14C years for recent samples). This is substantially better than we could achieve on our old instrument. Because of these facilities we are able to offer one of the highest levels of routine precision available at any radiocarbon lab.