English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Tools annual

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

Self-seeding is a promising approach to significantly narrow the SASEbandwidth of XFELs to produce nearly transform-limited pulses. Theimplementation of this method in the soft X-ray wavelength range necessarilyinvolves gratings as dispersive elements. We study a very compact self-seedingscheme with a grating monochromator originally designed at SLAC, which can bestraightforwardly installed in the SASE3 type undulator beamline at theEuropean XFEL. The monochromator design is based on a toroidal VLS gratingworking at a fixed incidence angle mounting without entrance slit. It coversthe spectral range from 300 eV to 1000 eV. The optical system was studied usingwave optics method (in comparison with ray tracing) to evaluate the performanceof the self-seeding scheme. Our wave optics analysis takes into account theactual beam wavefront of the radiation from the coherent FEL source, thirdorder aberrations, and errors from each optical element. Wave optics is theonly method available, in combination with FEL simulations, for the design of aself-seeding monochromator without exit slit. We show that, without exit slit,the self-seeding scheme is distinguished by the much needed experimentalsimplicity, and can practically give the same resolving power (about 7000) aswith an exit slit. Wave optics is also naturally applicable to calculations ofthe self-seeding scheme efficiency, which include the monochromatortransmittance and the effect of the mismatching between seed beam and electronbeam. Simulations show that the FEL power reaches 1 TW and that the spectraldensity for a TW pulse is about two orders of magnitude higher than that forthe SASE pulse at saturation.

Grating monochromator for soft X-ray self-seeding the European XFEL