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Monochromator beamline for FLASH
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Image of FIG. 1.
FIG. 1.

(Color online) Layout of the monochromator beamline PG2 for the VUV FEL.

Image of FIG. 2.
FIG. 2.

(Color online) Accessible range as function of first order energy with the (red) and (blue) gratings. Solid lines indicate values for simultaneous use of the specular beam in the PG0 branch, i.e., equal inclination angles of premirror and grating.

Image of FIG. 3.
FIG. 3.

(Color online) Typical SASE spectrum of a single pulse at the position of the exit slit. Vertical bar imitates exit slit. The width of the bar corresponds to a exit slit width. Monochromator settings: and .

Image of FIG. 4.
FIG. 4.

(Color online) Divergence of the FLASH beam in the standard mode with a pulse length of . The dots are results from a simulation of FLASH (Ref. 4). The solid line represents the divergence expected for a Gaussian beam. The dashed and dotted lines are assuming a dependency of the divergence from the photon energy.

Image of FIG. 5.
FIG. 5.

(Color online) Power density of the FEL radiation in on the first optical elements of the monochromator beamline for 30 and photon energies calculated with SHADOW (Ref. 13). Top to bottom shows mirrors M0, M1, M2, and the grating.

Image of FIG. 6.
FIG. 6.

(Color online) Spot image of the monochromator at exit slit for three different photon energies around . The resolution of the beamline is calculated from the width of the spot image.

Image of FIG. 7.
FIG. 7.

(Color online) Ray tracing results for the resolving power for the (a) and (b) gratings (dotted and dashed curves). The solid curve shows the result of an analytical calculation of the resolving power using a exit slit width for the given energy range limitation of the monochromator (see Fig. 2).

Image of FIG. 8.
FIG. 8.

(Color online) Reflectivity of different optical coatings in the energy range from . The reflectivity has been calculated for an incidence angle of 2° and in polarization. The hatched area is the possible higher harmonic energy range of FLASH up to .

Image of FIG. 9.
FIG. 9.

(Color online) Calculated transmission of the monochromator beamline with the (a) and (b) gratings for a monochromatic beam. Note the difference in scales on both panels.


Generic image for table
Table I.

Parameters of the optical elements of the beamline according to Fig. 1.

Generic image for table
Table II.

Calculated spot size and beam divergence at the focal point of the monochromator beamline in first and zeroth orders of the grating. Bottom line shows parameters of the zeroth order beamline.

Generic image for table
Table III.

Design parameters of FLASH under different operation conditions. The current mode of operation is the short pulse mode with a pulse width of [Ref. 4].


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Monochromator beamline for FLASH