Source-to-sample distance independent efficiency technique for XRF analysis

A technique to make the detection efficiency in XRF systems less dependent on source-to-sample distance is presented. It is shown that this dependence can be made more constant within a large range of distances if a properly calculated annular mask is used. Experimental results (for Ca, Ti, V and Zr), in good agreement with the calculated ones, are presented and show that constant efficiency values within ±5% can be obtained when the sample distance varies from 3 to 12 mm. However, peak absolute efficiencies are then reduced by a factor of about five.