Diffractometer Operating Procedure for CAD4 and CAD4-MACH
Make sure the shutter is closed before opening the radiation
protection enclosure!
- Open the radiation protection enclosure, screw the goniometer head
onto the instrument. Make sure the goniometer head is securely attached,
but don't screw the threads too tight.
- Enter the appropriate command into the instrument control computer
to bring the crystal to viewing position.
- Optically align the crystal.
- After the crystal is optically aligned, enter the appropriate
command to move the crystal into position for a preliminary rotation
photograph.
- Attach the photographic attachment to the goniometer and close
the radiation safety enclosure.
- Enter appropriate command to take preliminary rotation
photgraph.
- After the exposure is completed, open the radiation
safety enclosure and remove the photgraphic attachment.
- Close the radiation safety enclosure.
- Enter the command to begin search of reciprocal space for
diffraction maxima.
- After 20-25 peaks are found enter the command to index the
crystal.
- Decide on lattice symmetry for the sample. Transform and
re-index as necessary.
- Pick suitable reflections and test if Laue symmetry validates
your choice of cell.
- Select higher angle reflections and obtain higher precision
cell parameters. For best results, use reflections from all
eight quadrants.
- Examine peak shapes for several reflections at a variety
of sin(theta)/lambda values to choose best data collection
parameters.
- Choose data file names conforming to Facility conventions, and
open them.
- Enter data collection parameters.
- Start data collection.
- After data collection is completed collect psi scan data
and a final (high precision) set of cell parameters.
- Make sure shutter is closed, and open the radiation safety
enclosure. Remove your sample from the instrument.
- Close the radiation safety enclosure.
boyle@laue.chem.ncsu.edu
Last Updated 17 Sept. 1996