Changing the monochromator

Last modified by sjhuotar@helsinki_fi on 2024/02/07 06:21
  1. Write down to the logbook the date and time before starting, and write that: "Removing monochromator XXXX, replacing it with YYYY. X-ray kV and mA were: (check the kV and mA from the power source).
  2. Remove the old monochromator from the monochromator holder by gently loosening the top two plastic screws (1/2-1 turns are enough) and place it in its designated monochromator box.
  3. Choose the correct monochromator for your element and edge from the print-out list (todo: make an electronic list here to Wiki)
  4. Return the old monochromator to the monochromator storage and pick up the new one
  5. Insert the new monochromator to the holder and tighten the two top plastic screws gently by hand (gentle finger strenght is enough). Make sure it is firmly aligned with the back plate. Usually for the alignment there is a red arrow on the glass substrate of the monochromator, which designates the "top" position (align this with the small red arrow drawn on the support)
  6. Make a proper choice of x-ray power supply unit kV and mA. (Typically kV = 20 kV, mA = depending on the sample, minimum 2 mA). NOTE: For Ni, choose 10 kV / 2 mA; and for Mn, choose 9 kV / 2 mA.
  7. In spec, type "setmono", choose 0 to enter crystal type, and type when asked either Si or Ge, and enter the Miller indices in sequence separated by enter: h (enter) k (enter) l (enter).
  8. If conf.mac is not open, open it in Linux shell by typing "emacs /usr/local/lib/spec.d/spec6/conf.mac &" or in spec prompt by typing "u emacs /usr/local/lib/spec.d/spec6/conf.mac &" (remember the last  & - symbol: it is important)
  9. Find from conf.mac the old calibration of TH - Y - X  (dety and detx as a function of theta) for the desired edge; comment the old one out and uncomment the correct one.
  10. Quit spec (pressing CTRL-D or typing "quit" in spec prompt)
  11. Restart spec (keyboard arrow up button to recall the old command "spec6" from the command history, and press enter
  12. Move to somewhere in the spectral range (e.g. for Ni, "umv energy 8.333" and check the detx calibration:
    1. In spec: type the command "dscan detx -10 10 20 0.1"
    2. If the detx scan does not show a peak in the center of the scan, the calibration is wrong. Do the calibration as follows:
      1. umv th TH0 (check the value of TH0 from the conf.mac line)
      2. dscan detx -15 15 20 0.1; note down the FWHM center position and enter it to the conf.mac line for X0= value
      3. umv th TH1 (check the value of TH1 from the conf.mac line)
      4. repeat the above; also repeat it for th value TH2
      5. quit spec (CTRL-D or the command "quit") and restart spec (see above)
      6. umv energy 8.333 (or some other energy relevant for your edge)
      7. dscan detx -10 10 20 0.1
      8. Now the scan should be centered and have a flat top (fwhm about 5 mm).
  13. In principle one should check the vertical tilt alignment with the micrometer screw. This is an expert procedure and if not sure how to do it, just leave it.
  14. In principle you are ready to start your measurement. Check the Checklist before starting with a new sample or I0 measurement first.
  15. Write down to the logbook the date and time before starting, and write that: "Now monochromator YYYY in;  X-ray kV and mA are: (check the kV and mA from the power source)."
  16. The first measurement you do, should be a metal foil or other standard sample for checking the calibration. (instructions to change the calibration to be written here)