  The LEUTL FEL at the APS has achieved gain at 530 nm with peak beam current
\~100 A. In an effort to push to 120 nm and beyond, we have designed and are
commissioning a bunch compressor to increase the peak current to 600 A or more.
The bunch compressor uses a four-dipole chicane at an energy of 100 to 210 MeV.
To provide options for control of emittance growth due to coherent synchrotron
radiation (CSR), the chicane has variable R56. The central pair of dipoles is
movable, accommodating variable R56 with less concern about emittance dilution
from nonuniformity of the dipole field. The symmetry of the chicane is also
variable via longitudinal motion of the final dipole, which is predicted to
have an effect on emittance growth. Following the chicane, a three-screen
emittance measurement system should permit resolution of the difference in
emittance growth between various chicane configurations. A vertical bending
magnet analysis line is present to permit imaging of correlations between
transverse and energy coordinates. This paper reviews the features and expected
performance of the chicane. A companion paper discusses the physics design in
detail.
  Work supported by the U.S. Department of Energy, Office of Basic Energy
Sciences, under Contract No. W-31-109-ENG-38.
