Non-destructive geological core scanning using external beam ion beam analysis

Some issues relevant to the use of external beam ion beam analysis (IBA) at GNS for screening of geological cores were studied. These included the use of Ar X-rays produced in air to normalise the measurements and to gauge the window-sample distance, and an assessment of the sensitivity of the technique. Scans with a real core indicated that variations in the angle presented to the beam by the sample surface could significantly affect the results so further work was undertaken using two detectors viewing the sample from different angles. The new setup improved the reliability of the measurements by means of averaging the results from the two detectors. Typically in a scan of a 1 m long core over a period of about three hours elements from Ti to As can be measured at the level of from one to several hundred parts per million by weight and elements of greater atomic number in the parts per thousand range. The beam was focussed to a spot of approximately 3 mm diameter. (author). 4 refs., 16 figs., 2 tabs