Focussing set up for a microdiffraction experiment in 7ID-C in late July
Focussing set up for a microdiffraction experiment in 7ID-C
in late July 2002
Below are some pictures from setting up the CARS style KB mirror in the
MHATT-CAT 7ID-C hutch. To reach a spot size below 10 microns, the mirrors had
to be mounted directly on the Kappa input bench. These pictures show the set up
and the achieved spot size. The vertical spot size is a factor 3 wider than the
demagnified source size, but we believe it could be easily improved by a more
careful alignment. The KB mirror was installed about 0.5 m from the center of
rotation, and it should be possible in the future to focus down to around 2
microns, depending on the constraint of the sample environment and reciprocal
Special thanks should be given to Tom Trainer from GSECARS for giving us
access to his table record which worked very well and made the Kappa alignment
easy considering that the doubly reflected beam changes the propagation
direction of the incident beam. The MHATT-CAT team was lead in this important
technical achievement by Don Walko and included Jesse Guzman, Yoosuf Picard,
Eric Dufresne, and Steve Yahlisove.
Looking at the Kappa from downstream, the microscope (X5) was focussed
on the pin.
The pin removed, a thin YAG crystal was inserted in the plane of the PIN
and the YAG
surface is imaged on the CCD.
The YAG is mounted on a hole in the Al plate.
The KB-mirror system mount designed and fabricated by Jesse Guzman and
In front of the Kappa bench, mounted on the SAXS optical table, a slit
to 0.39 mm by 0.39 mm limits the beam on the KB mirrors.
Focussing was done in real time by looking at the video camera output on a
Before removing the goniometer pin, the pin outline was marked on
The focussed beam is on the tip of the pin.
The horizontal profile of the beam taken with an edge scan using a GaAs (100)
cleaved wafer. The horizontal spot size is 6 um FWHM. The demagnified
source size for this geometry is 5.3 microns. Clearly, the focal spot
matches the demagnified source size very well. The calculated horizontal
is 0.76 mrad.
The vertical profile of the beam taken with the same edge wafer.
was about 15 um FWHM in the vertical. The horizontal alignment was
carefully than the vertical one which we believe caused the large
The calculated vertical divergence is 0.63 mrad.