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. Fully tune the beam if you have detuned.
  3. Determine the energy of the desired absorption edge – consult Table 1-1 in the X-ray Data Booklet (“little orange book”).
  4. 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).
  5. Go to the XASUTILS window and select the tab that says “User Restore"


  6. 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.
    (example from 7-3, but the panel looks similar)
  7. 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.(example from 7-3 lists blocked out)
  8. When the restore is completed, wait 15-20 minutes for the beamline optics (m0 mirror) to thermally equilibrate with the X-ray heat load.
  9. 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).
  10. Go through the Restoring optimum M0 bend procedure listed in the document on Linux desktop.  This involves moving the M0BEND motor to three different absolute positions.
  11. Move the mono energy to the desired edge energy.
  12. 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 12.

-Move the MONO to (desired edge energy – 200 eV).

-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.

-Go to Calibrate -> Calibrate MONO in XAS Data Collector → MONO.  Set the current energy (where you saw the I2 decrease) to the desired edge energy.

13. Open S1VGAP to 10 mm and S1HGAP to 8 mm.\

14. Move MONO to (desired edge energy + 500 eV)

15. Scan M1VERT motor while looking at I0 signal.  Scan +/- 2 mm, with 0.2 mm point spacing (You can use rel2.argn in pre-set regions).  After scan, click on the maximum (centroid) of I0 and move M1VERT motor to this position.

16. Move MONO to (desired edge energy + 1000 eV).

17. In XASUTILS window, 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”).

18. Close S1VGAP to 1.0 mm and S1HGAP to 6.0 mm.

19. Scan TABLEVERT motor while looking at I0 signal.  Scan +/- 2.5 mm, with 0.2 mm point spacing.  After scan, click on the maximum of I0 and move TABLEVERT motor to this position. (Use rel2_5.argn in pre-set regions)

20. 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.

21. Move MONO above and below the edge energy and make sure that your signal is within a range of 0.3 and 4 V. If not, adjust the gains in xasutils → ion chambers.

22. If you adjust gains, remember to close beam and check offsets.

23. To run a calibration scan, in the XAS Data Collector → Regions panel, select a calibration region file from the pull-down list, or create a new one in using Region →  "Region Wizard" (this will open up a new tab) indicating the desired absorption edge, and "Foil" for an abbreviated edge region. Save and return to the main Data Collector window.

24. Create a single lined queue in the Queue Manager panel. Change the experiment line to use the detector file, region file, and number of sweeps (1) that you want to run.

25. Run calibration region file. Open the plotter and plot current.

26. 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).

27. Move MONO to energy of first derivative maximum.

28. Calibrate energy to desired edge energy in X-ray Data Booklet using Calibrate -> Calibrate MONO in XAS Data Collector → MONO

29. Select new SCA fluorescence windows in WebGe window.  Remember to "Update DXPs" when you're done, and Save SCA file with name of new absorption edge.

30. Begin collecting data!

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