VRML 3-axis spectrometer operation

snapshot

Following is a snapshot from the vrml browser with labels added to the control points.

vrml browser operation

Vrml browsers generally have 3 modes of mouse interaction with the scene which can be set from the keyboard: Examine mode (e key) uses button-1 to rotate the scene and button-3 to zoom; Walk mode (w key) uses button-1 or button-3 to translate the viewer across the scene; Fly mode (f key) uses button-1 to change the viewing angle and button-3 to zoom. These behaviours are not guaranteed and vary from browser to browser. Some browsers paste status information across the screen. This can obscure the scene so that you will typically want to remove it. In freewrl use the ``.'' (period-key). Typically browsers will supply help using the ``?'' (question-mark key).

control points and output

The incident and final neutron energies are adjusted by grabbing the red monochromator or analyzer crystals. Pressing mouse button-1 over the crystal should show a diamond shaped cursor, and then dragging the mouse will rotate the selected crystal. The scattering angle (twotheta adjustment) can be adjusted by grabbing the green sample table in the middle of the scene. The sample angle can be adjusted by grabbing the red box shape on top of the green sample table. The current values of the spectrometer settings are printed at the bottom of the scene. These values from left to right are the monochromator energy in meV, the components of the wave-vector transfer (Q) along the in scattering plane faces of the sample as Qx and Qy in inverse Angstroms, and finally the analyzer energy in meV. The bottom print out line contains the associated angles in degrees for the monochromator, sample, scattering angle twotheta and analyzer.

buttons

The following buttons are available for spectrometer control.

• Rx OFF/ON
  Pressing this button will turn ON/OFF the reactor which animates the flow of neutrons through the spectrometer. If the monochromator and analyzer energy settings are different you will see that the neutron velocity is different before and after the sample ( v K sqrt(E) ).
• prec
  Pressing this button will change the angle setting precision when dragging the control points.
• MODE inelast/elast
  The elastic MODE forces the monochromator and analyzer energies to be equal.
• monochromator d-spacing
  Selects a monochromator crystal reflection and associated d-spacing.
• analyzer d-spacing
  Selects an analyzer crystal reflection and associated d-spacing.

About this document ...

VRML 3-axis spectrometer operation

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