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OrientExpress

Test Laue neutron-diffractometer

The camera

Samples may be quickly and accurately aligned using the camera in the experimental zone.

Be sure that the lens cap is removed from the camera.

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Using NOMAD to view camera images

The camera is driven using NOMAD on the Linux machine.

To view the sample position with the camera:

  1. Choose the Settings tab in the left-hand panel of NOMAD.
  2. Select Instruments : Acquisition : Setting : LiveCamera
  3. A Delay of 100 ms is appropriate.
  4. Click the Play (►) icon in the bottom right of the NOMAD screen.

The green solid circle icon labelled Idle will change to a green open circle icon labelled Running.

Click on the View Image icon to open the camera window,

The beam axis and centre of rotation of the sample table are marked with a crosshair.

If the crosshair is not visible, click the Crosshair Icon on the top of the camera window.

The Linux machine has a monitor inside the experimental zone which mirrors the display outside the experimental zone.  Make sure that the camera window is visible in the Linux monitor and enter the zone.

 

IMPORTANT NOTE: 

The camera uses computer resources.  Once your sample is aligned, Stop (■) the camera by clicking on the appropriate button in the bottom right of the NOMAD screen.

The green open circle icon labelled Running will change back to a green solid circle icon labelled Idle.

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Manual adjustment

The sample stage has a number of stages for position and angle adjustment.

Use the Manual Position Adjustments for XY, and Z to centre the sample on the cross in the AMCap window.  

The sample support-to-beam axis distance is adjustable between 40 - 70 mm.   Any samples with mounts that are longer than 70 mm will not fit on the instrument!

Use the Coarse-adjust for omega to rotate the sample quickly by increments of 90°.  Again, use X and Y to align the sample on the cross in the AMCap window.

Your sample is now aligned.

If you wish, use the Fine-adjust for omega to orient your sample with respect to the incident beam.

IMPORTANT NOTES: 

The camera uses computer resources.  Once your sample is aligned, Stop (■) the camera by clicking on the appropriate button in the bottom right of the NOMAD screen.

The green open circle icon labelled Running will change back to a green solid circle icon labelled Idle.

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Trouble shooting

Camera not working?

The camera is the fastest and easiest way to align the sample.

If the camera does not work, call the instrument responsible.

In a pinch, it is also possible to use the pin and the 4 mm aperture from the useful drawer.

Be very careful with the procedure, as the detector is FRAGILE!

  1. Move the detector away from the sample to give yourself room.
  2. Carefully install the 4 mm aperture.
  3. Put the pin in the 4 mm aperture, with the point projecting 2 - 3 cm towards the sample.
  4. Carefully move the detector towards the sample.  
  5. The pin indicates the beam direction.  Align the sample relative to the pin.
  6. On completion, move the detector away from the sample, carefully remove the pin and install your appropriate aperture.
  7. Move the detector back to the desired sample-detector distance.

 

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