P432 – VLS-PGM SXR XFEL PAL
Application
Plane grating monochromator (PGM) for soft X-ray FEL radiation
Year of delivery
2016
Installation site
Soft X-ray beamline (XFEL) at Pohang Accelerator Laboratory, South Korea
This monochromator is an optimized version of the monochromator installed at the SXR beamline at SLAC (see project P308). The required grazing incidence at XFEL beamlines implies a large distance between pre-mirror and grating, which explains the stadium-shaped footprint of the vacuum chamber.
Design Features
-
High-resolution grazing incidence variable line spacing plane grating monochromator (VLS-PGM).
-
XFEL compatible.
- Spectral range: 270 – 1300 eV.
- Optical elements: one plane mirror and one VLS plane grating.
- Temperature sensors at internal mechanics, mirror and gratings holders.
- Four motorized B4C aperture blades at the PGM entrance flange.
-
Motion control system with EPICS interface.
- Permanently installed bakeout provisions.
- Adjustable support structure.
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
stadium shaped footprint
Main flanges
at the top
Material
1.4404 (C < 0.02%)
Base pressure
10-10 mbar range
Optical design parameters
Beam height (entrance)
1400 mm
Beam offset
17.46 mm
Number of plane mirrors
1
Plane mirror dimensions
300 mm x 60 mm x 60 mm
Number of gratings
1
Gratings dimensions
70 mm x 50 mm x 40 mm
Support structure
Adjustment ranges
Vertical translation
± 15 mm
Lateral translation
± 15 mm
Longitudinal translation
± 15 mm
Pitch
± 1°
Roll
± 1°
Yaw
± 1°
Mirror mechanics
Pitch rotation
Range
-2.60° to +1.5°
Resolution (design value)
0.004 µrad /motor fine step
(1/64, recommended)
0.0097087 µrad /encoder count
Resolution (measured value)
0.05 µrad
Repeatability
0.06 µrad (pitch)
0.16 µrad (roll)
Translation
Range
-46.7 mm to +70.4 mm
Resolution (design value)
0.06 µm /motor fine step
(1/256, recommended)
0.05 µm /encoder count
Repeatability
0.08 µrad (pitch)
0.16 µrad (roll)
Gratings
Pitch rotation
Range
-10.50° to +1.4°
Resolution (design value)
0.004 µrad /motor fine step
(1/64, recommended)
0.0097087 µrad /encoder count
Resolution (measured value)
0.05 µrad
Repeatability
0.08 µrad (pitch)
0.07 µrad (roll)
Long-term stability (45 minutes)
0.017 µrad
Translation
Range
-48.5 mm to +50.5 mm
Resolution (design value)
0.06 µm /motor fine step
(1/256, recommended)
0.05 µm /encoder count
Repeatability
0.14 µrad (pitch)
0.18 µrad (roll)
Aperture unit
Blades
Material
B4C
Range (for each blade)
± 3.5 mm
Resolution (design value)
0.156 µm /motor fine step
(1/64, recommended)
Performance Test Results
Pitch deviation after pitch change (mirror)
Roll deviation after pitch change (mirror)
Pitch deviation after pitch change (grating)
Roll deviation after pitch change (grating)
Pitch deviation after mirror translation
Roll deviation after mirror translation
Pitch deviation after grating translation
Roll deviation after grating translation
Mirror pitch positioning resolution
Grating pitch positioning resolution
Grating pitch long-term stability
Residual gas analysis
