[neutron-mc] Trouble with Single_Crystal

[Aaron M. Percival]

Hello all,
 
I'm having a little bit of trouble with the single_crystal component.  I've
created a .lau file in Crystallographica to simulate an Si analyzer crystal.
I simply want to reflect a neutron beam of wavelength 2.866 A using the 311
plane (d = 1.637) of Si.  So I've set up the crystal to satisfy the Bragg
condition, giving theta = 61.823, and thus 2theta = 123.646.  I put a banana
shaped detector around this 2theta, and I get no reflections.
 
Here is the crystal:
 
COMPONENT analyzer = Single_crystal(
    reflections = "Si.lau", xwidth = 0.1, yheight = 0.1,
    zthick = 0.01, delta_d_d = 0, mosaic = 18, order = 0,
    p_transmit = 0, absorption = 0, incoherent = 0, ax = 5.430530,
    by = 5.430530, cz = 5.430530, aa = 90, bb = 90, cc = 90)
  AT (0, 0, 0) RELATIVE a1
  ROTATED ( 0, theta311, 0) RELATIVE sample_arm
 
Where theta311 = 61.823 relative to the incident beam.
 
Can any one offer any suggestions as to why this might not be working?
I've also attached the Si.lau file.
 
Thanks, 
 
Aaron
 
 
*************************************************
Aaron M. Percival
M.Sc. Candidate
Dept. of Physics, Engineering Physics & Astronomy
Queen's University
Kingston, Ontario, Canada, K7L 3N6
Office: 613-533-6000 ext. 74789
Fax: 613-533-6463
*************************************************
 
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