  In present work we investigate the potential of a longitudinally focusing
device to compress bunches passing an undulator for a synchrotron storage ring.
If integrated into a storage ring similar to PETRAIII such device could
potentially produce continuous $\sim$1ps pulses of photons in the $nm$ range
with peak pulse powers of tens of GW. Even without operating in FEL saturation
mode the longitudinal focusing can provide means to increase the brightness and
shorten the photon pulse length.
