Capabilities of the SNAP Instrument

As general note, we have now moved to the MANTID software package for most of our data reduction. 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.
  • Powder crystallographic studies: higher resolution with detectors at 90o. First frame covers 0.5 < d< 3.0 Å. Higher frames can give data up 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. We can reach pressures up to 25 GPa between 85 and 320 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 (DAC) techniques for neutrons and have recently collected powder data on a simple system at room temperature up to 94 GPa. DAC pressure is applied using an external press with an inflatable membrane. This allows for the application of pressure in situ even when the press is connected to a CCR for low temperature studies (7-120 K). Additionally, we have done some high temperature studies (<700 K) in a DAC using external heating.

Please keep in mind that the systems available for study with a DAC are very limited. We need good scatters, simple crystal structures and sample packing. If you have an idea for a DAC experiment, please discuss it with an instrument team member before submitting a proposal.