Results of Interlaboratory Comparison Studies Conducted as Part of the Cronus-Earth Program

As part of the CRONUS-Earth study of cosmogenic nuclide production rates, we undertook an independent study of repeatability and reproducibility between different laboratories participating in the CRONUS-Earth program. In addition, laboratories participating in the CRONUS-EU program also took part. We distributed materials with high and low exposure ages for 10Be and 26Al measurements. In addition, we distributed two different 36Cl materials, one a carbonate and the other a K-feldspar to participating 36Cl laboratories. Our results to date indicate that we can constrain the interlaboratory 10Be errors below 5% for materials with high 10Be concentrations. The scatter in 26Al measurements is somewhat larger. We will discuss these and other observations, including the need for a longer-term intercomparison program. Preliminary field results have shown the existence of significant variability in results, some of which may be attributable to inhomogeneity in samples, laboratory procedures and measurement uncertainty. Therefore the role of the inter-comparisons to provide an empirical estimate of measurement uncertainty (inter and intra- laboratory) is crucial. Laboratories have been asked to make at minimum duplicate measurements. A substantial archive of material has also been created at the University of Arizona, which is an important outcome of the project, since this will be invaluable in further work.