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CHANGING ABSORPTION EDGES AT BEAMLINE 9-3

  1. Switch the calibration foil to the one for the new absorption edge.  Switch the filter in the holder on the Soller slits (if using one) to the Z-1 filter for the new absorption edge.
  2. Determine the energy of the desired absorption edge – consult Table 1-1 in the X-ray Data Booklet (“little orange book”).
  3. There are several cutoff energies for the M0 mirror – 10 keV, 13 keV, 15 keV, 23 keV, 29 keV.  Select a cutoff such that cutoff energy > (desired edge energy + 1000 eV).
  4. Go to the XASUTILS window (Linux machine) and select the tab that says “User Restore"
  5. From the pull down menu in the bottom left of page, select the user restore configuration that matches selected cutoff energy.  The target values for beam line motors will show up on the right side of the display.
  6. Hit the “Restore” button at the bottom of the XASUTILS screen.  Each of the motors in the list will be moved to its destination position.
  7. When the restore is completed, wait 15-20 minutes for the beamline optics (m0 mirror) to thermally equilibrate with the X-ray heat load. 
  8. During this time you could load a new sample, and put the correct new calibration foil between the I1 and I2 ion chambers (or on the backscattering photodiode).
  9. Go through the M0 bend optimization procedure (Note: SHOULD DOCUMENT AND LINK HERE) listed in the document on Linux desktop.  This involves moving the M0BEND motor to three different absolute positions.
  10. Move the mono energy to the desired edge energy.
  11. If the desired edge energy is > 15 keV, you will need to do a coarse calibration of the edge energy, and energy could be off by tens or hundreds of eV.  If the desired edge energy is <15 keV, the calibration should already be close enough for coarse calibration, so skip ahead to step 11.
    1. Move the MONO to (desired edge energy – 200 eV).
    2. Watch I2 while increasing MONO energy in relative steps of 10-20 eV.  When a sharp decrease in I2 is observed after one of these moves, you have reached the absorption edge of the foil.
    3. Go to Calibrate -> Calibrate MONO in xasscan program.  Set the current energy (where you saw the I2 decrease) to the desired edge energy.
  12. Open S1VGAP to 10 mm and S1HGAP to 8 mm.
  13. Move MONO to (desired edge energy + 500 eV)
  14. Scan M1VERT motor while looking at I0 signal.  Scan +/- 2 mm, with 0.2 mm point spacing.  After scan, click on the maximum (centroid) of I0 and move M1VERT motor to this position.
  15. Move MONO to (desired edge energy + 1000 eV).
  16. In XASUTILS window on Linux machine, select the “Mono Tuning” tab.  Move the tuning in one direction or the other while monitoring I0 signal, until you reach a maximum in I0.  Leave the tuning at this maximum, so the monochromator is 100% tuned (“fully tuned”).
  17. Close S1VGAP to 1.0 mm and S1HGAP to 6.0 mm.
  18. Scan TABLEVERT motor while looking at I0 signal.  Scan +/- 2 mm, with 0.2 mm point spacing.  After scan, click on the maximum of I0 and move TABLEVERT motor to this position.
  19. Scan TABLEHORZ motor while looking at I0 signal.  Scan +/- 3 mm, with 0.3 mm point spacing.  After scan, click on the maximum of I0 and move TABLEHORZ motor to this position.
  20. Move MONO to desired edge energy.
  21. Select a calibration region file from the pull-down list, or create a new one in xasscan using Region -> New and indicating the desired absorption edge.  In the region that is created, click on the first line and edit it to match the second line, then hit Apply.  Next remove the second and third lines, so there is only a single line in the region.  Save this as a calibration region file for the edge.
  22. Run calibration region file.  Plot log(I1/I2) versus energy, or if using scattering photodiode, create a custom plot of log(I0/I2) versus energy with denominator 1.  After the scan, select the Math tab and plot the first derivative.  Find the position of the first maximum of the derivative (the inflection point of the regular absorption data).
  23. Move MONO to energy of first derivative maximum.
  24. Calibrate energy to desired edge energy in X-ray Data Booklet using Calibrate -> Calibrate MONO in xasscan.
  25. Select new SCA fluorescence windows in xmapgui program.  Remember to Apply to All and Save SCA file with name of new absorption edge.
  26. Begin collecting data!
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