Development of a Monochromator System for the APS X-Ray BESSRC Beamlines Page: 2 of 8
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DEVELOPMENT OF A MONOCHROMATOR SYSTEM FOR THE APS X-RAY BESSRC
BEAMLINES
Mark. A. Beno, Gordon. S. Knapp
Materials Science Division, Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL
60439
Mohan Ramanathan
Experimental Facilities Division, Advanced Photon Source, Argonne National Laboratory,
9700 S. Cass Avenue, Argonne, IL 60439
ABSTRACT
We have designed a double crystal, fixed exit monochromator which allows
windowless operation of the APS beamlines. The crystals are mounted on a turntable
with the first crystal at the center of rotation. A mechanical linkage is used to correctly
position the second crystal and maintain a constant offset. The monochromator is
designed with two adjacent vacuum chambers, one containing the drive mechanism, a
vacuum compatible Huber goniometer, and another chamber containing a turntable on
which the monochromator linkage and crystals are mounted. The small annular
opening around a hollow stainless steel shaft which connects the Huber goniometer to
the turntable is the only passage between the two adjacent chambers. The design of the
monochromator is such that it can accommodate water, liquid nitrogen or galium
cooling for the crystal optics. The basic design for the monochromator linkage
mechanism is presented along with details of the monochromator chamber. The results
of initial optical tests of the monochromator system using tilt sensors and a precision
autocollimator will also be given.
I. INTRODUCTION
We have designed a double crystal, fixed exit monochromator with a constant
offset for UHV operations, thereby allowing windowless operation of the beamlines. A
mechanical linkage is used to correctly position the second crystal and maintain a
constant offset. The crystals are mounted on a turntable with the first crystal at the
center of rotation. The main drive for the rotary motion is provided by a vacuum
compatible Huber goniometer isolated from the main vacuum chamber. Rotary motion
of the primary monochromator stage is accomplished by using two adjacent vacuum
chambers linked only by the small annular opening around a hollow stainless steel shaft
which connects the Huber goniometer to the turntable on which the crystals are
mounted. This design allows high vacuum operation of the monochromator since it is
possible to maintain 10-9 Torr on the monochromator side while maintaining only 10-6
Torr in the goniometer vacuum chamber. The central shaft also allows for passage of
crystal cooling and electrical lines from UHV chamber to the low vacuum side and then
into the atmosphere. The design of the monochromator is such that it can accommodate
both water and liquid nitrogen cooling for the crystal optics.
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Beno, Mark A.; Knapp, Gordon S. & Ramanathan, Mohan. Development of a Monochromator System for the APS X-Ray BESSRC Beamlines, article, March 1, 1997; Illinois. (https://digital.library.unt.edu/ark:/67531/metadc689528/m1/2/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.