Jun 14 – 18, 2021
Europe/Stockholm timezone

Reinventing time-of-flight reflectometry—return of a proven approach

Jun 14, 2021, 7:15 PM




Tim Charlton


T. Charlton, H. Ambaye and A. Huon (ORNL)
M.R. Fitzsimmons (ORNL/University of Tennessee, Knoxville)

In this self-hosted Zoom-chat, I will discuss data acquisition and analysis techniques for neutron reflectometry at continuous wave (CW) sources applied to a pulsed-neutron source. I show data collected using the BL4A reflectometer at the Spallation Neutron Source (ORNL) using the so-called “CW-approach” and their analysis. The approach produces the reflectivity versus wavevector transfer without knowledge of the neutron beam spectrum. The results are compared to measurements of the same sample using the same instrument but with the traditional approach that involves normalization to the neutron beam spectrum typical of time-of-flight reflectometry. We find data acquired and analyzed using the CW-approach is less prone to instrumental artifacts than those obtained with the traditional approach and yields information that is more consistent with that obtained from X-ray reflectometry (at least for the sample studied). I discuss the implications of this study on how reflectometry data are collected at existing and proposed pulsed-neutron sources. I conclude with two parting and provocative questions:
• Why did the time-of-flight reflectometry and SANS communities take such radically different approaches to data acquisition and analysis?
• Given the success of the CW-approach, is a high frequency pulsed-source better suited for reflectometry than a low frequency source?

Work funded by the U.S. Department of Energy under contract No. DE-AC05-00OR22725.

Weblink to software and dataset in support of the presentation:

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