Neutron scattering is a powerful analytical technique for studying the structure and behavior of matter and is used in a range of applications including the study of quantum materials. Even at state-of-the-art neutron facilities, such as the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL), a small amount of distortion in measurements is often inevitable. However, ORNL researchers have now developed a new computational technique that can correct this distortion and improve revolution by up to 500% using open source software.
The “no cost” technique, which requires no additional hardware, was performed using ORNL’s MCViNE open source software, which can be used to emulate neutron experiments for spin waves measured by neutron instruments like the SEQUOIA at SNS. The team attempted to determine the amount of distortion inherent in SEQUOIA’s data collection and correct for this distortion in order to improve the effective resolution, said Jiao Lin, lead instrument development scientist for the CUPI2D neutron imaging source as SNS’s Second Target Station (STS). This task involved the challenge of determining the distortion across all four dimensions of the SEQUOIA measurements.
“To simplify the 4D measurements, we used MCViNE software to make 2D measurements along two axes at a time. We did that for both the distorted experimental image and the high-resolution idealized model we developed,” said Matt Stone, lead SEQUOIA instrument scientist at SNS. “We then repeated the 2D measurements along many other axes and interpolated the results to the approximate a 4D model. In this way we were able to measure the disparities between the actual image and our model.”
The team adapted a computational stereo vision technology to visualize the distortion along the different axes and compensate for the distortions in the original measurements one “slice” at a time. This process resulted in a resolution five times better than previous methods. A paper describing the super-resolution technique was published in Review of Scientific Instruments.
“Once we identified the amount and position of distortion in the data versus the idealized model, we were able to apply corrections to the data. We then used the corrected data set to generate a much more accurate spin wave dispersion that matched one of the known possible models,” said Gabriele Sala, lead instrument scientist of the STS CHESS beamline.
The researchers are confident the same approach can be applied to other neutron instruments and experiments. They also believe greater resolution and accuracy can be achieved by updating the 2D resolution technique to directly resolve 4D measurements.
Photo: The detector tank of the SEQUOIA neutron scattering instrument at ORNL's Spallation Neutron Source. Researchers used computational techniques and open source software to improve the resolution of SEQUOIA's spin wave dispersion measurements. Credit: ORNL