Development and application of the Los Alamos nuclear microprobe: hardware, software, and calibration

There is a great demand for spatially resolved quantitative trace element analyses of geologic samples. This class of samples is characteristically heterogeneous, fine grained, and compositionally complex. The Los Alamos nuclear microprobe has been developed for, and applied to, non-destructive in-situ geochemical analysis, primarily using the proton induced x-ray emission technique (PIXE). Characteristic x-ray spectra are acquired by bombardment with 1 to 200 nA beams of protons from the Los Alamos vertical Van de Graaff accelerator. Beam spot diameters of 10 μm are routine. After spectrum deconvolution, detection limits of approximately 5 ppM are obtained for an integrated charge on the order of 10 μC. Applications, concomitant with development have included analyses of meteorites, including one potential sample of Mars, terrestrial oil shales, archaeological artifacts, and ore mineral samples