Double-grating monochromatic beamline with ultrafast response for FLASH2 at DESY

Abstract

Edited by M. Zangrando, IOM-CNR and Elettra-Sincrotrone, ItalyKeywords: time-delay-compensated monochromator; diffraction; variable-line-spaced grating; free-electron laser. The preliminary design of a monochromatic beamline for FLASH2 at DESY is presented. The monochromator is tunable in the 50-1000 eV energy range with resolving power higher than 1000 and temporal response below 50 fs over the whole energy range. A time-delay-compensated configuration using the variable-line-spacing monochromator design with two gratings is adopted: the first grating disperses the radiation on its output plane, where the intermediate slit performs the spectral selection; the second grating compensates for the pulse-front tilt and for the spectral dispersion due to diffraction from the first grating.

FLASH and the FLASH2020+ project—current status and upgrades for the free-electron laser in Hamburg at DESY

“…FL26 hosts the fixed installation of a reaction microscope (ReMi) provided and supported by the Max-Planck-Institute for nuclear physics in Heidelberg [14]. FL23 is currently under commissioning and features a pulse-elongation-compensating double monochromator [15]. An SDU installation upstream in the FLASH2 hall can serve both beamlines FL24 and FL23 and provides delays up to twenty picoseconds between the split FEL pulses.…”

Spectrally tunable ultrashort monochromatized extreme ultraviolet pulses at 100 kHz

“…2). Existing TDC monochromators have two equally constructed stages with two identical gratings and correspondingly equal input (exit) arm lengths [53]. The use of the aforementioned annular geometry specifically designed for the high average power GHHG beamline, and the limited available laboratory space have motivated the construction of a novel, asymmetric monochromator.…”

Wavefront-propagation simulations supporting the design of a time-delay compensating monochromator beamline at FLASH2

“…For many research areas that require a narrower bandwidth of the photon pulse than the natural bandwidth of FLASH, ultrashort pulse lengths (<50 fs) and a high peak brightness are still prerequisites. An ultrashort pulse length can be preserved using a two-grating monochromator design (Poletto et al, 2018). To maximize the beamline throughput and transmission efficiency, the number of optical elements is minimized in the TDCM beamline.…”

“…The horizontal demagnification, given by a factor of $23, is however obtained by the product of the demagnification of the EM and the ratio of the distances from the slit to the first KB mirror and the focus distance given by the first KB mirror. The total length of the TDCM beamline including all elements (start-to-end) is 20.05 m. A first design was presented by Poletto et al (2018) and by .…”

“…high photon energy and ultrashort pulses. The present work aims to model and optimize the design concept described by Poletto et al (2018). By using wavefront simulations instead of ray tracing, further insights into the mechanical stability are provided and the optical quality required for each element can be defined.…”