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Tim Elam Senior Principal Physicist wtelam@apl.washington.edu Phone 206-685-3092 |
Research Interests
X-ray Spectroscopy
Biosketch
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.
Education
B.S. Physics, Mississippi State University, 1973
M.S. Physics, University of Maryland, 1977
Ph.D. Physics, University of Maryland, 1979
Projects
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Borehole X-Ray Fluorescence Spectrometer (XRFS) The XRFS was built by APL-UW under a NASA contract from the Langley Research Center; it is designed to be deployed down a pre-drilled hole for exploration and elemental analysis of subsurface planetary regolith. |
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Videos
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PIXL Blasts Off for Mars PIXL is an X-ray spectrometer integrated into the Perseverance rover that began its journey on July 30th. After landing in early 2021, PIXL will measure the microstructure of rocks in search of fossils and evidence of ancient Martian microbial life. |
15 Sep 2020
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PIXL on Mars 2020 Mission PIXL is the Planetary Instrument for X-Ray Lithochemistry. APL-UW's Tim Elam, the mission's 'chief spectroscopist', is collaborating with a NASA team that integrated a micro X-ray fluorescence instrument on the rover Perseverance that landed on Mars in February 2020. |
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24 Feb 2016
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PIXL's purpose is to measure the microstructure of rocks in search of fossils -- biosignatures of life forms preserved in the rocks. PIXL will tell scientists the composition of materials and their structure -- that is, how the elements are arranged. It's this map of elemental spatial distribution that's critical for finding biosignatures. |
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Ice Diver: A Thermal Ice Penetrator Ice Diver is a thermal melt probe system for extensive, low-cost sensor deployment to the bed of the Greenland Ice Sheet, where it will measure water pressure in subglacial hydrological networks. |
23 May 2013
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Publications |
2000-present and while at APL-UW |
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Microbial transport by a descending ice melting probe: Implications for subglacial and ocean world exploration Schuler, C.G., D.P. Winebrenner, W.T. Elam, J. Burnett, B.W. Boles, and J.A. Mikucki, "Microbial transport by a descending ice melting probe: Implications for subglacial and ocean world exploration," Astrobiology, EOR, doi:10.1089/ast.2021.0106, 2023. |
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6 Jun 2023 ![]() |
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Ocean Worlds beneath thick ice covers in our solar system, as well as subglacial lakes on Earth, may harbor biological systems. In both cases, thick ice covers (>100 s of meters) present significant barriers to access. Melt probes are emerging as tools for reaching and sampling these realms due to their small logistical footprint, ability to transport payloads, and ease of cleaning in the field. On Earth, glaciers are immured with various abundances of microorganisms and debris. The potential for bioloads to accumulate around and be dragged by a probe during descent has not previously been investigated. Due to the pristine nature of these environments, minimizing and understanding the risk of forward contamination and considering the potential of melt probes to act as instrument-induced special regions are essential. In this study, we examined the effect that two engineering descent strategies for melt probes have on the dragging of bioloads. We also tested the ability of a field cleaning protocol to rid a common contaminant, Bacillus. These tests were conducted in a synthetic ice block immured with bioloads using the Ice Diver melt probe. Our data suggest minimal dragging of bioloads by melt probes, but conclude that modifications for further minimization and use in special regions should be made. |
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Experimental validation of cryobot thermal models for the exploration of ocean worlds Pereira, P.D., and 19 others including D.P. Winebrenner and W.T. Elam, "Experimental validation of cryobot thermal models for the exploration of ocean worlds," Planet. Sci. J., 4, doi:10.3847/PSJ/acc2b7, 2023. |
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5 May 2023 ![]() |
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Accessing the potentially habitable subsurface waters of Ocean Worlds requires a robotic ice probe (or "cryobot") to traverse tens of kilometers of ice with temperatures ranging from ~100 to 273 K. Designing and planning such a mission requires understanding ice probe behavior as a function of the local environment and design parameters. We present experimental results of two laboratory melt probes in cryogenic (79 K) and warm (253 K) ice. The melt probe tested in warm ice had multiple adjustable heaters, enabling optimization of the system's efficiency. The melt probes tested in cryogenic ice operated in vacuum and had internal tether spools, allowing for experimental confirmation of hole closure and the creation of a pressurized pocket with liquid water around the probe. These melt probes were tested at power levels ranging from 120 to 1135 W, achieving descent speeds between 5.3 and 59 cm hr-1. By analyzing the relationship between power and speed using analytical and high-fidelity numerical models, we demonstrate progress in understanding melt probe performance. We distinguish between the previously confounding terms of probe operational inefficiency and analytical model inaccuracy, allowing us to understand the range of applicability of the analytical models and demonstrate the importance of controlling heat distribution in cryobot design. The validated models show that while numerical models may be required to describe the behavior of short probes descending in limited-size laboratory test beds, the performance of efficient cryobots designed for operation on Ocean Worlds can be predicted by analytical models within 5% error. |
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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 ![]() |
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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. |
In The News
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UW physics professor helps design instrument on Mars Perseverance rover KIRO Radio, MyNorthwest Staff University of Washington professor and physicist Tim Elam explained on KIRO Nights that he is part of a team that designed an instrument to create chemical images of rocks on Mars. Elam says he’s been working on his portion of this project for more than eight years, from the original proposal for the instrument to now having hardware on the way to Mars. |
18 Feb 2021
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How the pandemic is changing the protocol for NASA's Mars landing and how to watch it happen GeekWire, Alan Boyle Because of the yearlong COVID-19 pandemic, the hundreds of scientists and engineers behind the Perseverance rover mission have had to work almost exclusively from home. On the big day, only a minimal crew of ground controllers will be on duty at NASA’s Jet Propulsion Laboratory in Pasadena, CA. APL-UW Physicist Tim Elam, too, will be watching from home on February 18th. |
17 Feb 2021
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NASA's Mars Perseverance rover mission serves as ultimate test for working from home (planet) GeekWire, Alan Boyle Tim Elam is an expert on X-ray fluorescence at UW’s Applied Physics Laboratory. So when scientists and engineers were brought onto the team for Perseverance’s Planetary Instrument for X-ray Lithochemistry, or PIXL, Elam was a natural addition. |
29 Jul 2020
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