Neutrons Sciences Directorate at ORNL

Capabilities of the SNAP Instrument

As general note, we have now moved to the MANTID software package for most of our data reduction processing. This makes the reduction of raw data a much easier and automated process for most applications.

Current General Capabilities

  • Disordered materials studies (glasses/liquids/sloppy crystals at HP): low-resolution wide Q-range mode, 0.6<Q<23 Å-1, at temperatures between 90–300 K and pressures up to 10 GPa (higher if we use the larger PE press at room temperature, low temperature capabilities are still being developed for this press).
  • Powder crystallographic studies: higher resolution with detectors at 90 degrees. First frame covers 0.5<d<3.0 Å, higher frames can give data to d=8 Å; though note that the neutron beam intensity falls off rapidly at these wavelengths, i.e., you will need strong peaks in this range (0-25 GPa at room temperature, and 0-10 GPa between 85 and 300 K). Using a pure Zr gasket will allow measurement of weaker, long-wavelength reflections. However, pure Zr will pollute the spectrum with Bragg peaks up to d=2.8 Å. If a clean low-d spectrum is necessary, another sample in a TiZr gasket will have to be run. Keep this in mind when calculating the number of days needed for an experiment.
  • A modified piston for the PE cell allows resonance absorption line width measurements of samples held in a graphite furnace. This allows us to accurately determine the temperature of samples, while measuring in the high-resolution configuration up to 1500 K and ~6 GPa. This technique is currently restricted to powder samples.

Under Development

We are constantly developing diamond anvil cell techniques for neutrons and have recently collected powder data on simple systems at room temperature up to 78 GPa. We’ve successfully tested a gas-driven membrane clamp that allows us to make in situ pressure changes inside a CCR. While the membrane clamp behaves well, the CCR will have to be optimized. Recent tests baselined at 50 K and showed decreased performance as pressure increased. We have many ideas to improve the prototype and are confident that 20-30 K is not out of reach.

Please keep in mind that this is development work and is not yet widely available to general users. You can keep up with this work by visiting the Instrument Development Team blog.