  The aim of the FLASH linac is to create electron bunches of small transverse
emittance and high current for the free electron laser facility FLASH at DESY.
Available operational experience indicates that in order to optimize SASE
signal at different wavelengths or to fine-tune the FEL wavelength, empirical
adjustment of the machine parameters is required and, therefore, the
sensitivity of the beamline to small changes in the beam energy and in the
magnet settings becomes one of the important issues which affects both, the
final performance and the reproducibility of the results after breaks in
operation. In this article the transverse optics of the FLASH beamline with low
sensitivity to changes in beam energy and quadrupole settings is presented.
This optics is in operation since spring 2006 and has shown a superior
performance with respect to the previous setup of the transverse focusing.
