P470 – SGM SCS European XFEL
Application
Spherical grating monochromator (SGM) for soft X-ray synchrotron radiation
Year of delivery
2020
Installation site
SCS instrument of the European XFEL, Germany
This grating unit was developed and built to be integrated into the high energy resolution hRIXS system at SCS instrument of the European XFEL. The challenge was to accomodate all components for standard functionality and for compensation of spectrometer related spurious movements into a very limited space, without perfomance lost.
Design Features
- Grating unit for high resolution soft X-ray spectrometer.
- Spectral range: 250 – 1500 eV.
-
Very compact design for integration into the RIXS system.
- Optical elements: three spherical gratings.
- Temperature sensors at internal mechanics.
- Motorized and encoded entrance beam mask with different size apertures.
- Motorized and encoded vertical translation of the internal mechanics for compensation of spurious height and roll variation upon scattering angle change.
- Mechanically decoupled internal mechanics from the vacuum chamber.
- Internal mechanics directly connected to the adjustable support structure underneath.
- Permanently installed bakeout provisions.
Performance Features
- High positioning resolution (minimum incremental motion).
- High pitch rotation stability and repeatability.
- Minimized mounting induced deformations.
Outer Dimensions
Technical specifications and performance values
General
Vacuum chamber
Chamber type
rectangular footprint
Main flanges
at the top
Material
1.4404 (C < 0.02%)
Base pressure
10-10 mbar range
Optical design parameters
Beam height (entrance)
1410 mm
Number of gratings
3
Gratings dimensions
220 mm x 50 mm x 50 mm
Grating mechanics
Pitch rotation
Range
-7.30° to +2.53°
Resolution (design value)
0.0036 µrad /motor fine step
(1/64, recommended)
0.0097087 µrad /encoder count
Repeatability
0.13 µrad (pitch)
0.05 µrad (roll)
Long-term stability (1h)
0.06 µrad
Translation (grating exchange)
Range
-73 mm to +73 mm
Resolution (design value)
0.004 µm /motor fine step
(1/64, recommended)
0.05 µm /encoder count
Repeatability
0.32 µrad (pitch)
0.35 µrad (roll)
0.80 µm (position)
Long-term stability (5h)
0.008 µm
Translation (grating height)
Range
-2.24 mm to +2.07 mm
(wedge leveler 1)
-1.14 mm to +2.10 mm
(wedge leveler 2)
Resolution (design value)
0.40 µm /motor step (at actuator)
0.04 µm /motor step
(at wedge leveler)
0.05 µm /encoder count
Repeatability
0.22 µrad (pitch)
0.09 µrad (roll)
0.50 µm (position)
Long-term stability (3h)
< 0.10 µm
Performance Test Results
Pitch deviation after pitch change
Roll deviation after pitch change
Pitch deviation after grating lateral translation
Roll deviation after grating lateral translation
Pitch deviation after grating vertical translation
Roll deviation after grating vertical translation
Lateral position deviation after grating
lateral translation
Vertical position deviation after grating
vertical translation
Grating pitch stability
Grating pitch long-term stability
Grating vertical position long-term stability (left)
Grating vertical position long-term stability (right)
Grating lateral position long-term stability
