P423 – VLS-PGM SIX NSLS-II
Application
Plane grating monochromator (PGM) for soft X-ray synchrotron radiation
Year of delivery
2015
Installation site
SIX beamline at synchrotron radiation source NSLS-II, USA
This monochromator is part of the SIX beamline, dedicated to high resolution soft X-ray scattering experiments. Energy resolution and pointing stability are here of crucial importance. The long pre-mirror integrated in this monochromator required an adapted design to achieve the requested high 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: 150 – 2000 eV.
- Optical elements: one plane mirror and three VLS plane gratings.
- Temperature sensors at internal mechanics, mirror and gratings chin guards, mirror and gratings holders.
-
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 internal and external zero-order masks.
- 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 flange
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
19.25 mm
Number of plane mirrors
1
Plane mirror dimensions
500 mm x 50 mm x 70 mm
Number of gratings
3
Gratings dimensions
210 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
+1.6° to -12.3°
Resolution (design value)
0.00375 µrad /motor fine step
(1/64, recommended)
0.0047961 µrad /encoder count
Resolution (measured value)
0.50 µrad
Repeatability
0.15 µrad (pitch)
Long-term stability
0.027 µrad
Long-term stability with cooling water (2.2 l /min)
0.028 µrad
Scanning speed
~ 700 µrad /s
Grating mechanics
Pitch rotation
Range
+1.6° to -12.6°
Resolution (design value)
0.00375 µrad /motor fine step
(1/64, recommended)
0.0047961 µrad /encoder count
Resolution (measured value)
0.50 µrad
Repeatability
0.10 µrad (pitch)
Long-term stability
0.011 µrad
Long-term stability with cooling water (1.5 l /min)
0.012 µrad
Scanning speed
~ 700 µrad /s
Translation (grating exchange)
Range
-125 mm to +25.6 mm
Resolution (design value)
0.04 µm /motor fine step
(1/128, recommended)
0.05 µm /encoder count
Repeatability
0.06 µrad (pitch)
0.40 µrad (roll)
Baffle slits
Blades
Material
OFHC
Range
-2 mm to +25 mm
Resolution (design value)
0.10 µm /motor step
(full step at actuator)
Performance Test Results
Pitch deviation after pitch change (mirror)
Pitch deviation after pitch change (grating)
Pitch deviation after grating translation
Roll deviation after grating translation
Mirror pitch positioning resolution
Mirror pitch positioning resolution (2.2 l /min)
Mirror pitch long-term stability
Mirror pitch long-term stability (2.2 l /min)
Grating pitch positioning resolution
Grating pitch positioning resolution (1.5 l /min)
Grating pitch long-term stability
Grating pitch long-term stability (1.5 l /min)
Grating pitch stability for different water flow rates
Scanning speed of mirror pitch
Scanning speed of grating pitch
Residual gas analysis
