The Poisson alignment reference system implementation at the Advanced Photon Source. Page: 7 of 11
This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to Digital Library by the UNT Libraries Government Documents Department.
The following text was automatically extracted from the image on this page using optical character recognition software:
Calibrating the detector: The detector was mounted in a V clamp on a translation stage so that it
moved in the plane perpendicular to the beam. A 3-mm spot was obtained by moving the
collimating lens and by adjusting an iris placed between the mirror and the lens. Although the
iris caused a circular diffraction pattern in the spot, it was still used. The amplification on both
301 DIVs was set at 300 k. In order to limit the effects of transient air currents and vibrations,
each micrometer was moved by 0.01 mm and then 1000 samples were taken from both X and Y
position outputs at a sample rate of 10 kS/s. The average of the samples was used for each
calibration data point. The direction of translation was then switched, resulting in two lines for
each axis. The Virtual Bench Oscilloscope module was used to acquire the data. The rotation of
the detector was visually adjusted so that its X and Y axes were coincident with the X and Y
axes of the translation stage. One overhead neon bulb remained on with the side toward the
detector covered by black masking tape. The collimator lens was about 5 m away from the
detector. In total, 70 separate data sets were taken; however, the first 13 were discarded because
of initial errors in the setting of the micrometers.
Much time was invested in securing the equipment necessary for this project in order to
3.1 Phase One results
The interference patterns generated by the
three spheres are shown in Figure 4. Note that
the largest sphere created the smallest spot
while the smallest sphere created the largest
spot. Qualitatively, the diffraction patterns are
readily visible and the Poisson spots are easy to
distinguish. However, the downward sloping
waves covering the whole photograph indicate
some spurious interference caused by the
optical components. The effects are negligible
as compared to overall intensity.
The largest spot was chosen and monitored
using the oscilloscope software. An iris Figure 4: Poisson spots at 5 m from 0.09375",
coinciding with the first dark ring was placed 0.15625", and 0.1875" diameter spheres.
immediately in front of the detector to prevent
the detector from 'seeing' anything but the spot. As expected, the signal strength was quite low
even with a maximum amplification of 1 M. After all, the beam was expanded to 7.5 cm from
only a 3-mW laser. Even so, vibrations and moving air were readily apparent. Even placing a
hand under the beam shifted the spot noticeably since the heat caused a rising air current with a
different refractive index than the surrounding air.
Here’s what’s next.
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
Feier, I. The Poisson alignment reference system implementation at the Advanced Photon Source., article, September 21, 1998; Illinois. (https://digital.library.unt.edu/ark:/67531/metadc622121/m1/7/: accessed June 16, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.