Constant-strut-length hexapod
The constant-strut-length hexapod mechanism is well suited for mirror manipulation in UHV, especially for combined beam switching and beam splitting or for mirror exchange. The parallel-kinematic approach allows for free definition of the rotation center for pitch, roll and yaw, higher stability, repeatability and load capacity as compared to a stacked design. Mirror exchange units can be realized using a very compact design. The large rotational range travelled in a few seconds enables polarization switching e. g. for XMCD experiments.
Mechanism
In the Bestec constant-strut-length hexapod mechanism all actuators for the six degrees of freedom are located in-air (including motors, encoders and limit switches) and oriented vertically. The only moving parts are the in-UHV struts and the upper hexapod platform directly supporting the mirror and its holder. The UHV chamber stays fixed and is mechanically completely decoupled from the mechanism supporting the mirror.
Options
- Several mirrors exchangeable under UHV.
- Variable orientation and order of mirrors.
- Adjustable holders.
- Water cooling of mirrors.
- Temperature sensors at mirror holder and chin guard.
- Provisions for drain current measurements.
- Electrode for removal of low energy electrons.
- Motion control system.
Performance parameters
Performance parameter values for individual projects may well exceed the values listed below.
Rotations
Range
± 10°
Resolution
< 0.1 µrad
Repeatability
< 0.2 µrad
Speed
> 2° /s
Translations
Range
± 15 mm (horizontal), ± 90 mm (vertical)
Resolution
< 0.02 µm
Repeatability
< 0.10 µm
Speed
> 10 mm /s
Capacity
Load
up to 100 kg
Mirror length
up to 1200 mm
Performance Test Results
Mirror pitch repatability
Mirror roll repeatability
Mirror pitch repeatability after a large roll change
Encoder reading as a function of time
Applications
Mirror units in synchrotron radiation beamlines are used for deflection/focusing of the radiation beam and for absorption of unwanted power. Bestec mirror units allow for a motorized movement in six degrees of freedom covering exceptionally large ranges at very high speed and positioning repeatability.
