XRF spectrometer with a crystal monochromator improved by x-ray glass guides

FALCHINI, G.; MALEZAN, A.; POLETTI, M.; SÁNCHEZ, H.J.; PÉREZ R.D.

Brescia

Conferencia; 17th International Conference on Total Reflection X-Ray Fluorescence Analysis and Related Methods; 2017

Conventional x-ray fluorescence analysis (XRF) is a powerful instrumental technique for elemental quantification of samples with a wide range of matrices coming from industry, medicine, biology, environmental, archaeometry, etc.. The continuous part of the x-ray tube excitation beam is mainly responsible of the strong background in XRF spectra which restricts the detection limit to a few ppm (w/w). One possible strategy to reduce the detection limit is the monochromatization of the excitation beam with a crystal monochromator. In this case, the optimization of the system components is strongly required to obtain the highest excitation count rate over the sample, since the it is considerable reduced by the short energy band pass of the monochromator. In the present work a Si(100) crystal monochromator improved by x-ray glass guides has been developed. The x-ray guides are composed by several thin glass plate reflectors placed together and separated by spacers. Inside the gap, photons are transmitted by total reflection. One glass guide produces a low divergence parallel beam which impinges on the Si(100), and another one collect the monochromatic beam that emerges from the crystal. In this way the design of the monochromator is quite compact keeping a high photon flux at the output thanks to the wide acceptance section of the guides. The monochormator has been employed to select the Ka Mo line of a 3kW Mo x-ray diffraction tube. The spectrometer was used for trace analysis of biological tissues. The first results obtained in this field are shown in the present work where the performance of the spectrometer can be evaluated.