Ion Induced X-Rays for X-Ray Fluorescence Analysis

Abstract

Energetic ions bombarding pure element targets induce the characteristic x-rays with high probability and with negligible bremsstrahlung background. The cross sections for x-ray production by protons reach 103 b and heavy ions attain cross sections Z2 times higher. Small accelerators can produce monoenergetic X-rays from 1 to 20 kev with fluxes in excess of 1010/sr/μA of protons; heavy ion accelerators can achieve one to two orders of magnitude more. These Ion induced X-rays can be quite effective for X-ray induced X-ray fluorescence. For bulk samples, the method of IXX is as sensitive as PIXE itself; for many elemental analysis problems IXX may be the preferred technique. IXX enjoys the advantages of the widely used conventional x-ray induced x-ray fluorescence techniques: lighter constituents in heavy matrices can be effectively studied; liquid, even living targets can be used; heating and radiation damage are minimal; absolute quantitative analysis is straightforward even for oddly shaped samples. Focussed x-ray beams can be produced with considerably less background than can be obtained with EXX. IXX should be a valuable addition to the arsenal of analytic techniques available with present ion accelerators. We also remark that IXX facilities using stored beams of 20-30 MeV protons could produce monochromatic photon intensities of 1014 photons/sr/kW of power dissipated in the target. Such beams could be developed into x-ray probes competitive with any other technique for elemental analysis of small samples.