XRF microCT study of space objects at SSRL - art. no. 631825

Study of the composition and 3D chemical distribution of the particles that come from space are of great interest since they can provide information about the early stages and evolution of the solar system. The size of these samples varies with the smallest ones in the micron and even sub-micron range. X-ray fluorescence microCT (computed tomography) with focused X-ray beam can be successfully used to study these kinds of samples. This is especially important when sectioning is not feasible, or it is undesirable either due to the risk of contamination, as is the case with comet particles recently collected by the NASA Stardust mission, or the requirement for further analysis by different characterization techniques. X-ray fluorescence microCT measurements on several space samples were performed at the beamline 6-2 using the existing microprobe setup. Two mirror optical system is used for beam focusing with an additional set of KB mirrors located in the hutch near the sample to focus the beam further down to 2x4 microns. Incident X-ray energy is selected with a monochromator in the range of 5 to 20 keV. Fluorescence data was collected with Si(Li) fluorescence detector and PIN diode was used to collect attenuation data that provides additional information for fluorescence tomography reconstruction. The results of the measurements of two micrometeorites with sizes of approximately 100 microns, are presented.