MuCalc

The following overview is excerpted from: Hanna, R.D., and Ketcham, R.A. (2017) X-ray computed tomography of planetary materials: a primer and review of recent studies. Chemie der Erde – Geochemistry, 77, 547-572.

MuCalc is a Microsoft Excel workbook that can be used to compare the X-ray attenuation of various minerals. A mineral’s X-ray attenuation is primarily determined by its chemical formula and density, and the key to distinguishing between different minerals in a rock using XCT is to image at an energy where each mineral has a different X-ray attenuation (if possible). This workbook allows a user to determine if the various minerals in their sample will be distinguishable in the XCT data, and if there is an optimal energy at which to image in order to maximize their relative differences in attenuation. Within the workbook, the user selects the constituent minerals from a drop-down list and their X-ray attenuation versus energy (up to 500keV) are plotted together on a graph (see Figure for an example). The mass X-ray attenuation coefficients for the minerals in the workbook were retrieved using the NIST XCOM database, and the coefficients are multiplied by the mineral’s common density to obtain the final X-ray attenuation values.

The workbook currently contains a list of ∼250 common terrestrial and extraterrestrial minerals and native elements but detailed instructions are included on how to add a new mineral or element. In addition, there is a solid solution tool that can be used to define a new solid solution mineral out of existing minerals in the work- book and to add this to the permanent mineral list.