Checking Orbit on 9-ID
“Checking the orbit” is synonymous with checking the position of the x-ray beam incident on the 9-ID beamline with respect to its entrance mask FM103.
The procedure of determining the beam position consists of viewing the outline of FM103 on Flag1 with x-rays while tuning and detuning the undulator energy with respect to the monochromator energy. When the undulator is detuned its 4 lobes of radiation should be visible symetrically in the 4 corners of FM103, on approaching the monochromator energy the 4 lobes should converge in the center of FM103.
In case of a substantial deviation of the actual beam position from its intended position, the APS control room needs to be contacted through the floor coordinator with a request for an appropriate orbit correction.
The entrance mask FM103 is located at 26297 mm (nom.) from the undulator source, in the upstream section of 9-ID A (FOE), immediately downstream of the differential pump. Although it is mounted on a x-y motion stage, its position is kept fixed and centered on the fixed mask FM102, located in the middle of the differential pump.
FM103 provides a square aperture of size 2.1 x 2.1 mm2 with truly sharp corners.
With 9-ID A searched and secured:
- Open the undulator (gap ~ 45 mm)
- Open the Front-End Shutter
- Lower Flag1 into the beam (~ -26 mm or lower) and observe it on the “Flag1” monitor
[Flags] > [Flag #1] or [Motors FOE] > [17-24] > [Flag 1]
- Open the White Beam Slit to 2.1 x 2.1 mm2 (Yu/s = 0.9 mm, Yd/s = -1.0 mm, Xu/s = -2.1 mm, Xd/s = 0.9 mm)
[FM-WBS] > [WBS]
- Close undulator in small increments (5 mm) and observe convergence of beam within outline of fixed mask
- If center of intensity distribution is not in the center of the mask request orbit correction: call 2-0101, request correction in increments >= 5 urad