An XRD/XRF instrument for the microanalysis of rocks and minerals

A breadboard setup constructed at MOXTEK, Inc., is capable of capturing both x-ray diffraction (XRD) and x-ray fluorescence (XRF) information simultaneously using a charge-coupled device (CCD) as the x-ray detector. This preliminary setup will lead to a prototype simultaneous XRD/XRF instrument. NASA is funding the instrument's construction because of its capabilities and small size; it could be used for future Mars missions for analysis of rocks. The instrument uses a CCD to capture both the energy and the spatial information of an incoming x-ray. This is possible because each pixel acts as a spatially addressable energy-dispersive detector. A powdered sample of material is placed in front of the CCD, which in turn is bombarded by a collimated x-ray beam. The instrument's critical features-namely the x-ray source, collimation optics and x-ray transparent windows-allow for the first time, to the best of our knowledge, mounting the sample outside the CCD camera. In this paper the instrument's design parameters as well as the properties of both a front-side-illuminated (FSI) CCD and back-side-illuminated (BSI) CCD as x-ray detectors are investigated.