View Beamstop

• The beamstop obscures a part of an image.
• Reflections will not be generated (datcol) and peaks (peak2. peak3) will not be found behind the beamstop.
• The beamstop in view is build by a circle and a beamstopholder.
• Both circle and mount are defined in the laboratory system, positioned beamstopdistance mm behind the crystal.
• The beamstop can also consist of two beamstops connected with a small bar.

Single beamstop

Set beamstop dimensions

• Direct
  • Set the distance of the beamstop with beamstopdistance.
    A negative value value sets the distance relative to the detector distance.
  • Set the diameter of the circle with beamstopdiameter. Specify a negative value to disable the beamstop.
  • Set the width of the beamstopholder with beamstopwidth
• With the mouse
  • Use beamstopclick to mark several edgepoints of the beamstopcircle. The values of beamstopdiameter and the position(beamstop) will be calculated.

Set beamstop position

• Direct
  • Set the position of the beamstop with beamstop
  • Set the angle of the beamstopholder with beamstopangle.
    
  • You may position the circle independent from the beamstopholder with the command beamstopshift.
• With the mouse
  • Use beamstopclick to mark several edgepoints of the beamstopcircle. The values of beamstopdiameter and the position(beamstop) will be calculated.
  • Use beamstopset to mark the position of the beamstopcircle.

Double beamstop

• A second beamstop can be defined. Use the beamstop commands, as before, with a 2 appended to the command: beamstop2, beamstopangle2, beamstopdiameter2, beamstopshift2 and beamstopwidth2.
• Specify a negative value for beamstopwidth or beamstopwidth2 to disable one of the the beamstopholders.
• The relative position of the two beamstops can be changed with beamstoprot and beamstoprot2.
• The area between the two beamstops will also obscure the image if beamstopconnect is on. The width of this area is determined by abs(beamstopwidth) and abs(beamstopwidth2).

Tips and tricks

• Use drawbeamstop to plot the beamstop.
• Use save beamstop to write the beamstopinformation to a file beamstop.vic. On a next invocation of view, this file is automatically executed. You can copy the file to the calibration directory.
• You can play around with
  • beamstop =+0.1 = (move 0.1 mm to the right)
  • beamstop =-0.1 = (move 0.1 mm to the left)
  • beamstop = =+0.1 (move 0.1 mm up)
  • beamstop = =-0.1 (move 0.1 mm down)
  • beamstopdiameter =+1 (increase diameter)
  • beamstopdiameter =-1 (decrease diameter)
• Different beamstops for different scans.
  • Method 1
    • create different beamstop.vic files, f.e. beamstop1.vic and beamstop2.vic
    • Create a file datcols01fsetup.vic containing the command @beamstop1.
    • Create a file datcols02fsetup.vic containing the command @beamstop2.
    • The scan-specific setup files are automatically executed during the datcol process.
  • Method 2
    • Create beamstop.vic files for every scan: beamstops01f.vic, beamstops02f.vic....
    • The scan-specific beamstop files are automatically executed during the datcol process by datcolsetup.vic.