Processing actual multigrain diffraction data from a diamond anvil cell experiment

That's it, you have been trained in multigrain XRD data processing. You feel that you are ready for real data from a diamond anvil cell experiments!

Tough parts with diamond anvil cell data include

• shadows from the DAC itself,
• Compton background from the diamond anvils,
• single-crystal diffraction from the diamond anvils,
• typically, unknown phases and cell parameters,
• poor diffraction quality.

Obviously, unlike data from simulations, you do not know the answer! You do not know the grains you will be looking!

Here is a simple outline of what you should do:

1. Calibrate your experiment. This should be done with either Dioptas or Fit2D. Beam centers and detector distances you find in Dioptas or Fit2D will be used at a later stage of the processing.
2. Understand the concept of an O-Matrix and figure out your own.
3. We often also calibrate Maud as this point. We will use it later to figure out the cell parameters of our sample. As you start using MAUD keep a note of the parameters you use to convert your tiff images into ESG. You will need to use exactly the same ones on your sample images later.
4. Later, for each P/T point you wish to study
   • Remove bad images and replace them with either the average of the two surrounding images or create an empty image,
   • Calculate an average and a median image,
   • Use MAUD or Dioptas or anything else to identify your phases and their cell parameters. We often work on the average images to do so,
   • Clean up your data for diamond diffraction spots, DAC shadows, etc
   • Search for peaks,
   • Calculate your G-Vectors,
   • Index your grains with GrainSpotter!
   • Treat side phases first (e.g. pressure medium, pressure marker, other phases)
   • …