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Tim Elam

Senior Principal Physicist





Research Interests

X-ray Spectroscopy


Dr. Tim Elam's main research interest is X-ray spectroscopy. He has worked in the areas of X-ray absorption, emission, fluorescence, and non-resonant inelastic scattering. His present efforts focus on using X-ray fluorescence in difficult environments. He has built several downhole X-ray fluorescence spectrometers to measure heavy metal contaminants in soils and sediments and to make in-situ measurements of diffusion of stable isotopes of nuclear waste elements through native rock without radioactivity. He is now the Chief Spectroscopist for the Planetary Instrument for X-ray Lithochemistry (PIXL) on the Perseverance rover and the hardware lead for the APL-UW Ice Diver.

He is past Chair of the Denver X-ray Conference and was the American Institute of Physics Congressional Science Fellow for 1991. He has more than 100 publications in refereed scientific journals and holds 5 patents.

Department Affiliation

Polar Science Center


B.S. Physics, Mississippi State University, 1973

M.S. Physics, University of Maryland, 1977

Ph.D. Physics, University of Maryland, 1979


2000-present and while at APL-UW

A statistical approach to removing diffraction from X-ray fluorescence spectra

Orenstein, B.J., D.T. Flannery, L.W. Casey, W.T. Elam, C.M. Heirwegh, M.W.M. Jones, "A statistical approach to removing diffraction from X-ray fluorescence spectra," Spectrochim. Acta, Part B, 200, doi:10.1016/j.sab.2022.106603, 2023.

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1 Feb 2023

Diffraction peaks can lead to inaccurate elemental abundances in X-ray fluorescence maps. However, manually removing diffraction peaks is laborious while existing automated methods unnecessarily remove significant volumes of fluorescence data. Here we propose a new automated method to remove diffraction from multiple-detector spectra based on a statistical threshold. This method eliminates only the diffraction peaks from the spectra, retaining more of the fluorescence data and increasing the information content available for diffraction-free elemental quantification and mapping. By retaining the majority of the fluorescence data, the proposed method does not require an increase in dwell times or additional data to be collected to compensate for the removed fluorescence data. This method is therefore particularly valuable in instances where measurement time and data volumes are highly restricted, such as for instruments on planetary exploration missions like the Planetary Instrument for X-ray Lithochemistry on NASA's Mars 2020 mission Perseverance Rover.

The focused beam X-ray fluorescence elemental quantification software package PIQUANT

Heirwegh, C.M., W.T. Elam, L.P. O'Neil, K.P. Sinclair, and A. Das, "The focused beam X-ray fluorescence elemental quantification software package PIQUANT," Spectrochim. Acta, Part B, 196, doi:10.1016/j.sab.2022.106520, 2022.

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1 Oct 2022

Adoption of a robust X-ray fluorescence spectroscopy quantification and spectrum fitting routine calls for careful consideration on the inner workings and databases incorporated in its architecture. For analysis of micro-XRF data returned from the Planetary Instrument for X-ray Lithochemistry (PIXL), integrated on the Mars 2020 Perseverance rover, the University of Washington and the National Aeronautics and Space Administration (NASA) have invested in the production of an in-house micro-XRF software package, PIQUANT, capable of supporting quantitative elemental analysis of whole rock and geological materials. The PIQUANT software uses an iterative fundamental parameters physics-based model to convert X-ray peak intensity into elemental concentration, and has minimal reliance on calibration using standards. It also incorporates polycapillary optic transmission correction to account for photon passage in the X-ray optic of micro-XRF systems. This work introduces the key features of PIQUANT's architecture, its databases, models, assumptions and summarizes features available as part of the analysis products it generates. A working example of a quantification process available with this software is presented within.

An olivine cumulate outcrop on the floor of Jezero crater, Mars

Liu, Y., and 71 others including W.T. Elam and K. Sinclair, "An olivine cumulate outcrop on the floor of Jezero crater, Mars," Science, 377, 1513-1519, doi:10.1126/science.abo2756, 2022.

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25 Aug 2022

The geological units on the floor of Jezero crater, Mars, are part of a wider regional stratigraphy of olivine-rich rocks, which extends well beyond the crater. We investigate the petrology of olivine and carbonate-bearing rocks of the Séítah formation in the floor of Jezero. Using multispectral images and x-ray fluorescence data, acquired by the Perseverance rover, we performed a petrographic analysis of the Bastide and Brac outcrops within this unit. We find that these outcrops are composed of igneous rock, moderately altered by aqueous fluid. The igneous rocks are mainly made of coarse-grained olivine, similar to some Martian meteorites. We interpret them as an olivine cumulate, formed by settling and enrichment of olivine through multi-stage cooling of a thick magma body.

More Publications

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center