P392 – VLS-PGM ESM NSLS-II
Application
Plane grating monochromator (PGM) for soft X-ray synchrotron radiation
Year of delivery
2015
Installation site
ESM beamline at synchrotron radiation source NSLS-II, USA
The long pre-mirror integrated in this monochromator required an adapted design to achieve the requested high repeatability and stability of mirror and grating pitch rotations. Special attention was payed to block zero-order and stray light by using several water cooled masks and beam stops.
Design Features
-
High-resolution grazing incidence variable line spacing plane grating monochromator (VLS-PGM).
- Spectral range: 15 – 1500 eV.
- Optical elements: one plane mirror and four VLS plane gratings.
- Temperature sensors at internal mechanics, mirror and gratings chin guards and mirror body.
-
Active water cooling of all optical elements.
-
Two piezo actuators at the sine-bar rotation mechanisms.
- Four water cooled, motorized and electrically isolated OFHC baffle blades at the exit flange.
-
Water cooled entrance and external zero-order masks and beam stop.
- 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
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)
1400 mm
Beam offset
40 mm
Number of plane mirrors
1
Plane mirror dimensions
585 mm x 60 mm x 70 mm
Number of gratings
4
Gratings dimensions
190 mm x 40 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
+0.35° to -20.3°
Resolution (design value)
0.0037 µrad /motor fine step
(1/64, recommended)
0.0047961 µrad /count
Repeatability
0.09 µrad (pitch)
0.13 µrad (roll)
Scanning speed
~750 µrad /s
Grating mechanics
Pitch rotation
Range
+0.6° to -26°
Resolution (design value)
0.0037 µrad /motor fine step
(1/64, recommended)
0.0047961 µrad /count
Resolution (measured value)
0.05 µrad
Repeatability
0.08 µrad (pitch)
0.06 µrad (roll)
Stability
0.010 µrad
Stability (1.4 l /min cooling water)
0.014 µrad
Scanning speed
~800 µrad /s
Translation
Range
-22 mm to +224.5 mm
Resolution (design value)
0.04 µm /motor fine step
(1/128, recommended)
0.05 µm /encoder count
Repeatability
0.12 µrad (pitch)
Aperture unit
Blades
Material
OFHC
Range
-2 mm to +15 mm
Resolution
0.10 µm /step (full step)
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 grating translation
Grating pitch positioning resolution
Grating pitch stability
Grating pitch stability (1.4 l /min)
Grating pitch stability for different flow rates
Scanning speed of mirror pitch
Scanning speed of grating pitch
