[neutron-mc] NOP

[wokaoyan1981 at 126.com]

Hello Lucia,

Thank you very much for your reply! I understand the unexpected output 
when you shed light on it.
Now I take an angular scan as you suggest, here is part of the result:
( Si 311, 
  TDS=0, 
  Debye Waller factor=-288,
  Linear cell expasion=1, 
  Mosaic Crystal=No,
  Geo=BRAGG diffr beam, 
  Scan type=Theta(absolute),
  Energy/Wavelenghth unit=Wavelenggh(angstrom), 
  Angular Unit=Degrees, 
  Fixed value=1.2, 
  Min scan Value=20,
  Max scan Value=25, 
  Scan Points=1000, 
  Asymetry angle=0, 
  Crystal thickness=0.6999)
              ...
      21.4911 6.11795e-006
      21.4916 7.52919e-006
      21.4921  0.000120346
      21.4926  0.000303971
      21.4931 6.50051e-005
      21.4936  0.000526068
      21.4941 5.63596e-006
      21.4946  0.000368681
      21.4951   0.00645020
      21.4956    0.0147543
      21.4961  0.000430623
      21.4967  0.000171211
      21.4972   0.00121510
      21.4977  0.000588131
      21.4981  0.000492101
      21.4986  0.000255239
      21.4991 2.99586e-005
      21.4996 1.94318e-005
      21.5002 9.97257e-005
      21.5007  0.000119835
      21.5012 8.19391e-005
      21.5016 3.93121e-005
      21.5021 1.48155e-005

            ...
And I see the Bragg peak near 21.5 degree.
My question is: Then how should I get reflectivity file from the data above?Integral or something else? Actually, I don't clearly understand the reflectivity file required.

Yours sincerely,
Tom


在2008-04-25，"Alianelli L (Lucia)" <lucia.alianelli at diamond.ac.uk> 写道：

Hi Tom,
 
it seems that the energy scan type is not optimised in NOP. So I would suggest you look at angular scans, i.e. rocking curves.
 
I attach the rocking curve for lambda = 0.04 nm. The Bragg angle is about 7 degrees, not 21.5. At 21.5 deg you would find zero intensity.
 
Of course you are going to get an error when trying lambda = 0.7 nm or 7 Angstrom. The reason is that the Si 311 d-spacing is 1.64 Angstrom, so you cannot find any Si 311 Bragg reflection for such cold neutrons!!!!
 
Also are you interested in perfect crystal reflectivity? 
Or reflectivity from a mosaic or bent crystal? 
 
Regards,
 
Lucia
 
 
If you want to look at theory, measurements and simulations of neutron reflectivity from crystals, you can look at the bibliography in my thesis:
http://www.esrf.eu/computing/scientific/people/srio/publications/alianelli_thesis.pdf 
 



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