P495 – SGM FURKA SwissFEL PSI
Application
Spherical grating monochromator (SGM) for soft X-ray radiation
Year of delivery
2022
Installation site
ATHOS beamline at Swiss FEL, Paul Scherrer Institut, Switzerland
This grating unit was developed and built to be integrated into the RIXS system for ATHOS beamline at SwissFEL of Paul Scherrer Institut. 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: 200 – 2000 eV.
-
Very compact design for integration into the RIXS system.
- Optical elements: three spherical gratings.
- Temperature sensors at internal mechanics.
- 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)
1320 mm
Number of gratings
3
Gratings dimensions
290 mm x 50 mm x 50 mm
320 mm x 50 mm x 50 mm
350 mm x 50 mm x 50 mm
Grating mechanics
Pitch rotation
Range
+0.5° to -3.0°
Resolution (design value)
0.001 µrad /motor fine step
(1/128, recommended)
0.0097087 µrad /encoder count
Resolution (measured value)
0.025 µrad
Repeatability
0.07 µrad (pitch)
Long-term stability (> 4h)
0.012 µrad
Translation (grating exchange)
Range
-59.3 mm to 119.6 mm
Resolution (design value)
0.078 µm /motor fine step
(1/128, recommended)
0.005 µm /encoder count
Resolution (measured value)
10 µm
Repeatability
0.14 µrad (pitch)
0.06 µrad (roll)
0.52 µm (lateral position)
Absolute accuracy
< 110 µm
Long-term stability (> 3h)
0.004 µm
Translation (grating height)
Range
-20.82 mm to +6.80 mm
(wedge leveler 1)
-20.96 mm to +7.11 mm
(wedge leveler 2)
Resolution (design value)
0.20 µm /motor step (at actuator)
0.054 µm /motor step
(at wedge leveler)
0.05 µm /encoder count
Resolution (measured value)
5 µm (vertical translation)
Repeatability
0.13 µm (pitch)
0.12 µm (roll)
< 1 µm (height)
Absolute accuracy
< 20 µm
Long-term stability (> 3h)
< 0.02 µm
Roll rotation
Range
± 15 mrad
Resolution (design value)
0.20 µm /motor step (at actuator)
0.054 µm /motor step
(at wedge leveler)
0.05 µm /encoder count
Resolution (measured value)
5 µrad (roll)
Repeatability
0.20 µm (pitch)
0.22 µm (roll)
0.45 µm (vertical position)
Parasitic height after
roll rotation
0.46 µm
Entrance flange mask
Translation
Range
-46.63 mm to +46.62 mm
Resolution (design)
0.039 µm /motor fine step
(1/128, recommended)
0.05 µm /encoder count
Performance Test Results
Pitch deviation after pitch change
Grating pitch long-term stability
Pitch deviation after roll change
Roll deviation after roll 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
Vertical deviation after grating vertical translation
Vertical deviation after roll variation
Lateral deviation after grating lateral translation
Absolute accuracy of grating lateral translation
Grating pitch positioning resolution
Grating pitch step width
Grating roll positioning resolution
Grating roll step width
Grating lateral translation positioning resolution
Grating lateral translation step width
Grating vertical translation positioning resolution
Grating vertical translation step width
Grating lateral position long-term stability
Residual gas analysis
Grating vertical position long-term stability
