Optimization of a simple X-ray diffraction instrument for portable and planetary applications

The constraints placed on the design of portable and planetary X-ray diffraction (XRD) instruments by the limited mass, power and volume budgets are very different, in general, to the constraints applicable to laboratory equipment. A relatively simple angle-dispersive, reflection-mode instrument design with no moving parts is used to illustrate some optimization methods using Monte Carlo ray-trace modeling and theoretical calculations. Utilization of parafocusing is an important aspect of the optimization. An Fe-55 radioisotope X-ray source is assumed, and it is shown that commercial, off-the-shelf sources are not optimal in their design for XRD applications. The geometrical parameters relating to the source and to a simple collimating aperture are subjected to an optimization process, which keeps both the flux incident on the sample and the size of the parafocusing circle constant. (C) 2010 Elsevier B.V. All rights reserved.