P408 – Mirror Unit SISSY_soft EMIL BESSY
Application
Mirror unit (M4) for soft X-ray synchrotron radiation
Year of delivery
2015
Installation site
EMIL soft X-ray beamline at BESSY, Helmholtz-Zentrum Berlin, Germany
This soft X-ray split mirror unit is part of the combined hard and soft X-ray EMIL beamlines at BESSY. It features an optimized design of the constant-strut-length hexapod mechanism used for the first Bestec hexapod (see project P377). The mirror splitting is realized by a vertical movement. The vacuum chamber accomodates not only the actual beam but also the passing hard X-ray beam of the neighbouring branch.
Design Features
-
Constant-strut-length hexapod mechanism.
- Six degrees of freedom and selectable rotation center.
- Spectral range: 80 – 2000 eV.
- Optical elements: two focusing mirrors.
- Electrodes at mirrors surfaces for carbon contamination prevention.
-
Provisions for RF oxygen plasma cleaning of the optical surfaces.
- Provisions for measuring the photocurrent at each mirror.
- Beam diagnostic unit at the exit flange.
- Permanently installed bakeout provisions.
- Adjustable support structure.
Performance Features
- High positioning resolution (minimum incremental motion).
- High stability and repeatability for all degrees of freedom.
- 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
1420 mm
Number of mirrors
2 (3 mirror slots)
Surface shape
ellipsoidal
Mirror dimensions
420 x 50(40) x 40(5) mm3
Actuator drives for hexapod axes
Resolution (design value)
0.004 µm /motor fine step
(1/128, recommended)
0.005 µm /encoder count
Mirror mechanics
Pitch rotation
Range
± 8 mrad
Resolution (measured value)
0.05 µrad
Repeatability
0.13 µrad (pitch)
0.20 µrad (roll)
Long-term stability (1h)
0.05 µrad
Roll rotation
Range
± 10 mrad
Resolution
0.05 µrad
Repeatability
0.08 µrad (pitch)
0.30 µrad (roll)
Long-term stability (1h)
0.04 µrad
Yaw rotation
Range
± 8 mrad
Resolution
0.05 µrad
Long-term stability (1h)
0.04 µrad
Vertical translation (switch)
Range
± 75 mm
Horizontal translation
Range
± 5 mm
Aperture unit
Blades (manual)
Material
OFHC
Stroke
25 mm, 50 mm
Spindle pitch
1 mm
Performance Test Results
Pitch deviation after pitch change
Roll deviation after pitch change
Pitch deviation after roll change
Roll deviation after roll change
Mirror pitch positioning resolution
Mirror pitch long-term stability
Mirror roll long-term stability
Mirror yaw long-term stability
Residual gas analysis
