  Although microbunching-instability (MBI) based synchrotron-radiation
facilities do not exist yet, the prominent presence of this space-charge driven
instability in the high-brightness accelerator facilities promotes the ongoing
worldwide effort to mastering it. Thereby not only the possible countermeasures
but also the applications of MBI are in focus of the research. So far, the
observed microbunching wavelengths are in IR or optical regime. Shifting the
microbunching towards shorter wavelengths seems to require either very
high-bunch peak currents or extremely small emittances. These extreme
characteristics are difficult to generate and hard to preserve. This letter
proposes a novel magnetic device which allows to amplify the initial shot noise
at wavelengths in EUX and XUV range with moderate peak current and emittance.
It consists of permanent magnets. The specific combination of focusing
channels, dispersive chicanes and single focusing elements in this device
allows for optimal amplification of microbunching by the longitudinal-space
charge-impedance. Extensive simulation studies for different beam energies show
the performance of the proposed device, which fed for example with an energy
recovery linac can provide ultra-short coherent-high power-radiation pulses
with a high repetition rate.
