1994 User's Group Meeting -- A Look At The PGM
A highlight of the annual SRC Users Group meeting was the demonstration of a
working prototype of the new Plane Grating Monochromator (PGM) design, which
will be used with the 7-250 eV undulator, scheduled for delivery in January
The PGM has some unique design elements, that have not been used before in a
synchrotron beamline. The central concept behind the PGM is a mechanical
coupling of the relative translation and rotation between the mirror and the
grating. This means that the diffraction angle changes as the wavelength is
scanned. By making the grating translate and rotate, rather than the mirror as
in previous designs, the mirror mechanism becomes much simpler. This is
important, since the mirror intercepts a high power density from the undulator,
and must therefore be water cooled.
Attendees at the Users Group meeting were treated to a demonstration of the
unusual mechanical design of the PGM by Mike Fisher of the Engineering Group.
The bench tests of the prototype use a Zygo interferometer, which can
characterize the mechanical precision of the motions of grating and mirror. It
is also used to evaluate the interferometric feedback system that will be used
to maintain monochromator accuracy during scanning.
Aladdin -- Editor Brian Tonner firstname.lastname@example.org