Diffractometer Operating Procedure for CAD4 and CAD4-MACH

1. 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.

2. Enter the appropriate command into the instrument control computer to bring the crystal to viewing position.

3. Optically align the crystal.

4. After the crystal is optically aligned, enter the appropriate command to move the crystal into position for a preliminary rotation photograph.

5. Attach the photographic attachment to the goniometer and close the radiation safety enclosure.

6. Enter appropriate command to take preliminary rotation photgraph.

7. After the exposure is completed, open the radiation safety enclosure and remove the photgraphic attachment.

8. Close the radiation safety enclosure.

9. Enter the command to begin search of reciprocal space for diffraction maxima.

10. After 20-25 peaks are found enter the command to index the crystal.

11. Decide on lattice symmetry for the sample. Transform and re-index as necessary.

12. Pick suitable reflections and test if Laue symmetry validates your choice of cell.

13. Select higher angle reflections and obtain higher precision cell parameters. For best results, use reflections from all eight quadrants.

14. Examine peak shapes for several reflections at a variety of sin(theta)/lambda values to choose best data collection parameters.

15. Choose data file names conforming to Facility conventions, and open them.

16. Enter data collection parameters.

17. Start data collection.

18. After data collection is completed collect psi scan data and a final (high precision) set of cell parameters.

19. Make sure shutter is closed, and open the radiation safety enclosure. Remove your sample from the instrument.

20. Close the radiation safety enclosure.