Microprobe x-ray fluorescence with the use of point-focusing diffractors

A toroidal point-focusing mica crystal diffractor was used to focus monochromatic x rays from a microfocus x-ray source operated at 0.1 mA and 30 kV, The Cu K-alpha x-ray focal spot of 50 mu m x 85 mu m had 1.6 x 10(4) photons/s/mu m(2). Microprobe x-ray fluorescence (MXRF) spectra were recorded with a Si(Li) energy dispersive detector for bulk specimens of GaAs. Si, and Muscovite. Low background due to monochromatic excitation resulted in predicted detection limits as low as 2 ppm for a measurement time of 500 s. Laboratory MXRF systems based on point-focusing diffractors were shown to provide lower detection limits. larger working distance, and higher theoretical intensity than systems using capillary optics. (C) 1997 American Institute of Physics.