attached below is a MPEG movie I made today FYI.
It shows the main beam in 7ID-D at the end of the
two theta arm in 7ID-D, so about 59 m from the source
apertured by a 2mm x 2mm slit in 7ID-D.
There are 547 files,
no feedback on the first 200 files
then feedback on the next 250 so file ~200-450,
and finally no feedback for the last ~100 file from 450-547.
These CCD full frames were taken at 2.5 Hz with the DP-HQ camera with a X2
objective and thick YAG:Ce. The MPEG movie does not show the timing
appropriately unfortunately. It displays frames at 30 Hz whereas I took them
at 2.5 Hz. So its duration is only 18 s while the movie lasted 219 s in real
time. I'll try to figure out ways to improve this. Suggestions are welcome.
N.B. the main beam at the bottom has structure due to Kapton windows.
The beam typically after some time burns Kapton and one can see
spatial structure on the main beam. Note that much of the beam profile
stays in place while the illumination moves around so some structure is
associated with the windows while some by the monochromator beam motion.
I made this movie using a program on hydra called "ppmtompeg".
If you are interested to know more, let me know. If you use other tools
for moviemaking, please let me know asap. This is pretty crude as a tool.
Attachment #2 shows the Horizontal beam position derived from the
center of mass of the CCD image in microns. We see a 1.26 micron rms motion
in 219 s sampled at 2.5 Hz.
Attachment #3 shows the Vertical beam position derived from the
center of mass of the CCD image in microns. We see a 2.48 micron rms motion.
Whether the feedback is on or not is not observable here, likely because
the feedback is not sensitive enough to correct for such small motion.
It works of course for large beam motion following an energy change!