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Flat sample alignment procedure

Below is the procedure to align a flat sample on the MCX beamline. The parts in bold refer to plugins in the MCX control software. You can find the plugins in the lower left part of the main program window. 

  1. Close the shutter
  2. Move theta and 2-theta to zero degrees using Diffractometer->four-circle controller
  3. Open Beam/Station status->filter/shutter controller and put down filters 3,4,5 and 6 (3.7mm Al)
  4. If the X-ray energy is higher than 12 keV, you need to put additional Al filters in front of the detector. Ask the beamline personel how much.
  5. Close ther hutch 
  6. Start the Measurement->Intensity monitor if you are using the scintillator detector, or the Measurement->XGLab monitor if you are using the MCA
  7. Open the shutter and look at the count-rate. If you see  more than 100,000 counts, close immediatley the shutter. You have to add more Al filters!
  8. Move the sample down (usually 5mm is enough) using the Diffractometer->Sample stage controller. (Check carefully which axis you need to move!)
  9. Check the count rate (Itot) in the detector. If possible, raise filters in the Beam/Station status->filter/shutter controller until a reasonable count rate is observed 10,000-50,000.
  10. Now move the sample up until only half of the count rate is left.
  11. Open the script window Other->Run script. Click "Load" go to the folder Alignment and select theta-scan.py (or theta_scan_XGL.py, when using the MCA detector).
  12. Click 'Run'. The script will now perform a scan of theta. At the angle theta where count rate is the highest the sample is parallel to the beam.
  13. Put theta on the value where the maximum count rate was observed. Now set theta to zero. (Both using  Diffractometer->four-circle controller). If there was non maximum, but a plateau at one end of the scan, move theta to this end-angle and set zero there
  14. Repeat step 10 to 13 until the maxuimum is at theta zero, and the count-rate at theta zero is half of the total count rate (Itot)
  15. MOVE 2-THETA TO 2 DEGREES
  16. You now have aligned the sample. Don't forget to remove the Al filters!
Last Updated on Wednesday, 29 May 2013 16:24