P378 – VLS-PGM UPBL7 ESRF
Application
Plane grating monochromator (PGM) for soft X-ray synchrotron radiation
Year of delivery
2014
Installation site
UPBL7 beamline at European Synchrotron Radiation Facility, France
This is the first monochromator built by Bestec with a liquid nitrogen cooling system, which was developed in cooperation with ESRF. At a temperature around 120 K, the expansion coefficient of silicon is close to 0. Therefore, a temperature distribution with strong variation does not lead to a significant deformation of the optical surface.
Design Features
- High-resolution grazing incidence variable line spacing plane grating monochromator (VLS-PGM).
- Spectral range: 300 – 2000 eV.
- Optical elements: one plane mirror and four plane gratings.
- Temperature sensors at internal mechanics, mirror and gratings holders.
-
Cryogenic cooling (LN2) of the plane mirror.
- Active water cooling of the gratings.
- Mechanically decoupled internal mechanics from the vacuum chamber.
-
Motorized precision vertical translation of the internal mechanics.
- Adjustable support structure.
- Permanently installed bakeout provisions.
Performance Features
- Extremly 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
cylindrical, vertical axis
Main flanges
at the top
Material
1.4404 (C < 0.02%)
Base pressure
10-10 mbar range
Optical design parameters
Beam height (entrance)
1394.5 mm
Beam offset
15 mm
Number of plane mirrors
1
Plane mirror dimensions
450 mm x 70 mm x 100 mm
Number of gratings
4
Gratings dimensions
200 mm x 40 mm x 30 mm
Support structure
Adjustment ranges
Vertical translation
± 15 mm
Motorized fine vertical translation
± 1 mm
Lateral translation
± 15 mm
Longitudinal translation
± 15 mm
Pitch
± 1°
Roll
± 1°
Yaw
± 1°
Vertical translation
Range
-1.0 mm to 2.68 mm
(wedge leveler hall side)
-0.8 mm to 2.86 mm
(wedge leveler ring side)
Resolution (design value)
0.03 µrad /motor fine step
(1/64, recommended)
0.05 µm /encoder count
Plane mirror
Pitch rotation
Range
1.32° to -8.55°
Resolution (design value)
0.0036 µrad /motor fine step
(1/64, recommended)
0.0097087 µrad /encoder count
Resolution (measured value)
0.50 µrad
Repeatability
0.40 µrad (pitch)
Long-term stability (4h)
0.01 µrad
Scanning speed
~ 680 µrad/s
Translation
Range
-7.20 mm to +54.58 mm
Resolution (design value)
0.0586 µm /motor fine step
(1/256, recommended)
0.05 µm /encoder count
Repeatability
0.30 µrad (pitch)
0.70 µrad (roll)
Gratings
Pitch rotation
Range
1.15° to -11.32°
Resolution (design value)
0.0036 µrad /motor fine step
(1/64, recommended)
0.0097087 µrad /encoder count
Resolution (measured value)
0.01 µrad
Repeatability
0.08 µrad (pitch)
Long-term stability (4h)
0.008 µrad
Scanning speed
~ 700 µrad
Translation
Range
-10.55 mm to +214.92 mm
Resolution (design value)
0.0586 µm /motor fine step
(1/256, recommended)
0.05 µm /encoder count
Repeatability
0.13 µrad (pitch)
0.17 µrad (roll)
Performance Test Results
Pitch deviation after pitch change (mirror)
Pitch 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 positioning resolution
Grating pitch positioning resolution
Grating pitch positioning resolution
(with/without cooling water)
Grating pitch deviation during stabilisation for different cooling water flow rates
Mirror pitch long-term stability
Grating pitch long-term stability
Mirror pitch scanning speed
Grating pitch scanning speed
Residual gas analysis
