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Source of wonder

The next installment from Gerard and the lab staff at 14CHRONO, Queen's University Belfast

Radiocarbon measurements are carried out in the ‘source’ region of our AMS (top). There, graphite targets are bombarded with Cesium ions (charged particles that can be accelerated using voltages and electric fields). This causes sputtering (emission) of carbon ions from the graphite target. These carbon ions get sped up or accelerated by electric fields down into the beamline for measurement. With all the cesium and graphite bombardment going on, over time the source itself becomes dirty and will start introducing contamination into our measurements. So we periodically need to open up the source and clean inside. We also have to remove the source assembly, take it apart, clean all the components and reassemble it before it can go back into the source. Here’s one we have just cleaned up (bottom). We normally carry this out every one or two months.

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