X-ray Fluorescence Particle Size and Scattering Angle Considerations Preparatory Experiments for the Calibration and Interpretation of C1XS Data

摘要

ISRO’s Chandrayaan-1 mission to the Moon is due to be launched in April 2008. Part of its payload is C1XS, a compact X-ray fluorescence (XRF) spectrometer which will provide high quality elemental mapping of the lunar surface [1]. In flight, the input source (solar X-ray spectrum) will be measured by the accompanying XSM payload [2]. An ‘in-house’ IDL XRF modelling code (referred to as the ‘C1XS XRF code’ [3]), which is based on the methods of [4], will be used to convert the C1XS data from X-ray fluxes into elemental ratios and abundances. This study outlines a plan of testing the accuracy and robustness of the code, using XRF spectral data from well characterised geological samples. We aim to quantify how XRF intensity varies with changing particle size and phase angle (θ in Fig. 1) geometry, in order to simulate changes in the solar aspect angle (angle between the Sun, the lunar surface and the detectors), as well as surface topography. These issues have previously been studied within a materials science context e.g. [5 – 9], but rarely but rarely for heterogeneous, geological samples [10 – 12].