An upgrade of the Argonne-Minnesota beamline was recently completed, one year after its
starting date. The addition of a Seya monochromator to the existing ERG (Extended Range
Grasshopper) monochromator has expanded the spectral range of the beamline to lower energies
(5 - 40 eV).
The combination of an ERG and a Seya signifies a unique capability - two types of electron
spectroscopy, core and valence, may be performed at once. This is possible because the
focus of both monochromators is at the same spot. The low energy photons provided by the
Seya monochromator are used for the valence electronic structure studies, and are valuable
for high-resolution angle-resolved photoemission experiments.
The performance of the upgraded beamline has been tested with angle-resolved photoemission
measurements on platinum foil, and the high-Tc superconductor YBa2Cu3O7. The flux and
resolution results are within the range of expectation.
The somewhat unusual ERG/Seya combination was originally designed and implemented by Cliff
Olson on the Ames-Montana beamline at Aladdin. Rong Liu from Argonne National Laboratory
was chiefly respon-sible for construction of the duplicate project, while Olson played an
important consulting role. The optics, engineering and accelerator operations groups of
SRC provided valuable advice and technical assistance. SRC benefits from the second
ERG/Seya beamline by its ability to accommodate more experimental projects which require a
wider spectral range.
Rong Liu commented on the project by saying, "Most of the difficulties stemmed from the
unique task of combining two monochromators into one beamline. In addition to making them
fit physically, we had to align the common refocusing mirror in such a position that two
beams could be focused at the same spot."