G2 Vertical Four-circle Line-up Procedure

part A: diffractometer
  1. line up pin hole in the center of rotations (COR) on the phi-circle
  2. level the optical table
  3. move tth to zero and mount line-up laser in the detector holder
  4. open detector arm slits wide to let laser beam pass
  5. adjust detector holder such that the laser beam hits the pin-hole in the COR
  6. close the detector arm slits symmetrically around the laser beam to 2mm x 2mm

part B: side-bounce monochromator
  1. take burns upstream and downstream of Laue crystal to verify that it is centered on the beam
  2. line-up Laue crystal using I0 ion chamber without the s0 slit
  3. mount s0 slit on the ttha arm in front of the ion chamber and set it to 2mmH x 1mmV
  4. check with the transit that slit s0, crystal and beam are at the correct heigths
  5. line up ttha arm with respect to s0 slit
  6. check manual tilt of the crystal by moving +/- 0.2 deg using the Nonius on the goniometer

part C: mono and diffractometer
  1. remove ion chamber and slit; set up two manual slits with 2mmH x 20mmV on the ttha arm so that they are centered on the dove tail
  2. wheel the optical table of the diffractometer around to roughly shoot the laser beam through both slits on the ttha arm; when you get through the first slit you are usually close enough
  3. fine align diffractomater translation (using the motorized xtable axis) and rotation (turning one of the ytable axes by hand) - this will take a couple of iterations
  4. move the diffractometer to the right height using the DC motors of the feet; make sure to level the table repeatedly when you get close to the right height
  5. try to shoot the laser beam through the s0 slit onto the crystal; you may have to do some more fine alignment of the table (xtable to translate, one of the ytable axes to rotate)
  6. set-up an ion chamber or diode monitor behind the pinhole and scan the x-ray beam from the side-bounce crystal using xtable and zsam; if xtable is off, move to the optimum position; if zsam is off; try to correct the table height a bit with the three DC motors
  7. set-up a NaI detector and scan the detector arm (tth) through the x-ray beam passing the pinhole; the maximum defines the absolute zero of tth
  8. remove the pinhole, set up a sample, and have fun!
laser lin-up