Mirror and Metrology Laboratory

Synopsis

The Mirrors and Metrology Group provides mirror systems used in the optics hutches of ESRF beamlines. Starting from the design and components selection, the optics group subcontracts the manufacturing of the mirrors, coatings and mechanical assemblies. It then qualifies the performance of the systems with respect to the specifications in the optics metrology laboratory. In the case of microfocusing Kirkpatrick-Baez devices, the group manages the production, integrates all the components of the system and characterizes the quality, including beamline performance.

Optics mirror and metrology laboratory

The primary aim of this laboratory is to measure the surface quality of optical components to be installed on beamlines. Although the main activities are for the measurement of mirrors and/or associated bending devices, the laboratory also performs surface characterisation of other optics (particularly monochromator and analyser crystals).  It is equipped to perform surface quality measurements at the highest level of accuracy, from the full length of the mirrors (up to 1.5 m) down to nanometer features. It is located in a 56 m² class 1000 clean room, temperature controlled within 1°C with a local class 100 area. Shapes as diverse as elliptical or toroidal can be measured.

Our main capabilities are summarized in the description of the instruments:

• Long trace profiler (LTP)
  A custom-built laser instrument measuring the deflection by the mirror of a scanned beam with an optoelectronics sensor. Lateral resolution of 2 mm over a range of 1.5 meters with a slope error precision better than 0.2 µradian rms. Specific software developments permit, for example, the automatic figuring of benders towards a programmed elliptical shape.
• Veeco NT9300 Micro-interferometer
  3-D surface measurements over small areas operating using either white-light or phase shifting interferometry. Its height resolution of 0.5 Angstrom with lateral resolution better than one micron allows the evaluation of the roughness of supersmooth polished surfaces needed in X-ray optics. The instrument incorporates advanced stitching capabilities, allowing the mapping of surface topographies at the nm height scale with sub-micron lateral resolution over areas extending over tens or even hundreds of millimeters in length.
  
• Zygo Verifire AT+ Fizeau interferometer
  3D mapping of large radii surfaces with a precision of a few nanometers over a 150 mm area. The instrument is currently equipped with transmission flats and a 1m radius transmission sphere. Measurements of large aperture (>150mm) optics can be performed in the double pass configuration using oblique incidence and a reflexion flat.
• Other instruments
  
  • Small Twymann-Green interferometer (FISBA DCI2): mapping of smaller curvatures.
    
  • SIS atomic force microscope: study of surface topography at the nanometer level.

Nanofocusing reflecting systems
(Kirkpatrick Baez - KB)

Several types of bending systems have been developed: 76 to 300 mm long mirrors, coated with either metals or multilayers produced in the ESRF multilayer lab can be combined to perform a desired microfocusing task. More than 70 benders have been produced at the end of 2010, in close collaboration with the mechanical engineering group. A standard KB system is delivered with eight motors permitting the alignment and focusing operations. A beam position CCD sensor, part of the system, allows the dynamic elliptic shaping of the mirrors. Constant refinements of the technology have permitted to focus the source down to a spot size of 80 nanometers diameter with 4x10¹¹ photons/seconds at 20.5 kev. Standard ESRF KB systems have been licensed and are commercially available.