The resolution function in direct geometry neutron chopper spectrometers are fascinating. They exist up to 4 dimension in powder and single crystal experiments.
Super resolution phonon Density of States from the ARCS instrument, a neutron Direct Geometry Chopper SpectrometerRead More
published in Science on Oct 9, 2015. https://science.sciencemag.org/content/350/6257/193.
From Wikipedia: “A glacier is a persistent body of dense ice that is constantly moving under its own weight; it forms where the accumulation of snow exceeds its ablation (melting and sublimation) over many years, often centuries”
- Glacier erosion has obvious effects on the landscape of the Earth
- Glacial erosion rates span several orders of magnitude from polar and dry regions to temperate alpine glaciers, and from hill-slope landscapes to steep, tectonically active mountain ranges
Glacier erosion power law was proposed by Jonathan Harbor, Bernard Hallet, and Charles Raymond, Nature, 1988.
But what is value of b, the power factor?
Sub-pixel image correlation techniques for satellite imagery were developed and used in this study to obtain accurate 3D model of the glacier surface, and then its moving speed, u, and helped constrain the value of b.
- ~50k lines of python/C++ code for Satellite Image Correlation
- Include the full DEM workflow of ancillary data correction (bundle correction), tie-points generation, orthorectification, correlation, triangulation, and gridding
Flux and elastic resolution for a wide range of instrument conditions were measured and modeled for the ARCS chopper spectrometer.
This work provides a key reference for users of the ARCS instrument, making it easier for users to plan for their experiments. The online interactive resolution/flux plots make it much easier for ARCS users to take educated tradeoff between resolution and flux, while taking their experiment requirements into account.
- A series of vanadium calibration measurements for a wide range of incident energies were performed for the ARCS direct geometry chopper spectrometer
- Analytical models were able to reproduce most of the general trends observed in the measurements.
- MCViNE simulations were used to confirm modeling results when experimental results are not reliable for direct measurement of resolution
This work was published at https://doi.org/10.1016/j.physb.2018.11.027.
A snapshot of a neutron CT reconstruction.
Neutron has greater penetration depths and has different cross section dependency on elements than X-ray. Neutron tomography can be used to study a variety of larger samples and is finding applications in engineering, material science, biology, and archeology. This package is in use by ORNL neutron imaging beamlines for neutron CT reconstructions.
- Detector geometry calibration was performed using powder Si and C60 calibration datasets to better determine the positions and orientation of detector packs in the SEQUOIA instrument.
- Positioning of some detector packs were significantly improved
A website for this calibration work is at https://sns-chops.github.io/SEQ-IDF-12292017/