The contamination of optical elements (mirrors and gratings) with carbon still is an issue when using soft x-ray synchrotron radiation. With an in-house developed HF-plasma treatment we are able to decontaminate our optics in-situ from carbon very efficiently. The cleaning device, a simple Al-antenna, is mounted in situ inside the mirror- and grating vacuum chambers. A systematic study of the HF-plasma cleaning efficiency was performed acquired with in-situ and exsitu methods for monitoring: An atomic force microscope (AFM) and a scanning tunneling microscope (STM) were used before and after the cleaning process to determine the surface morphology and roughness. Reflectivity angular scans using the reflectometer at the BESSY-II Metrology Station [1-3] allowed to estimate the thickness of the remaining Clayer after different cleaning steps and thereby helped us to determine the etching rate. Reflection spectra measurements in the range of 200 eV – 900 eV show the complete removal of Carbon from the optics without contaminating it with any other elements due to the plasma treatment. The data show that the plasma process improves the reflectivity and reduces the roughness of the surface. In addition to that, the region of the optical surface where the carbon has been removed becomes passivated.
The design for a new XUV-Optics Beamline is presented. The collimated plane grating monochromator (PGM-)
beamline at a bending magnet is setup at the BESSY-II synchrotron radiation facility within the framework of the
blazed-grating production facility. Coupled to a versatile four-circle (ten axes) UHV- reflectometer as a permanent end
station the whole setup is dedicated to at-wavelength characterization and calibration of the in-house produced precision
gratings and novel nano-optical devices as well as mirrors, multilayered systems etc. It is also open to external projects
employing reflectometry, spectroscopy or scattering techniques. According to its purpose, this beamline has specific
features, such as: very high spectral purity, provided by two independent high order suppression systems, an advanced
aperture system for suppression of stray light and scattered radiation, a broad energy range between 10 eV and 2000 eV,
small beam divergence and spot size on the sample. Thus this Optics Beamline will become a powerful metrology tool
for reflectivity measurements in s- or p-polarisation geometry with linearly or elliptically polarized light on real optics up
to 360 mm length and 4 kg weight.
Within our technology center for production of highly efficient precision gratings a versatile 4-circle UHV-reflectometer
for synchrotron radiation based at-wavelength characterization has been fabricated. The main feature is the possibility to
incorporate real live-sized gratings. The samples are adjustable within six degrees of freedom by a novel UHV-tripod
system, and the reflectivity can be measured at all incidence angles for both s- and p-polarization geometry. The
reflectometer has been setup in a clean room hutch and it is coupled permanently to the optics beamline PM-1 for the UV
and XUV range with the polarization adjustable to either linear or elliptical. The setup will be open to users by the end of
We present new experimental data on diffraction efficiency measurements on gratings for the first undulator beamlines
at BESSY II. The measured data will be compared with results from electromagnetic theory. A good suppression of higher orders, i.e. the sum of higher orders from higher energies which are diffracted into the same angle as the first order, has been an important point during the design process of the beamlines at BESSY II. For this purpose lamellar grating structures have been optimized and specified. The measurements were carried out with a triple axis vacuum diffractometer at the BESSY I PM 4 beamline in an energy range from 70 to 1200 eV. We measured the diffraction efficiencies of the first order and the corresponding second and third order at discrete energies E, i.e. second and third order efficiency at 2E and 3E respectively. To improve the accuracy of the measurements, the higher orders from the PM 4 beamline had to be taken into account. We used a calculation scheme starting at the highest energy, in which the diffraction efficiency of the grating under test and the higher orders from the monochromator have been evaluated simultaneously. The calculated higher orders of the monochromator were then recursively used as input for the calculation at lower energies. The gratings were measured at different angular settings, hence enabling different
degrees of high order suppression. It was determined, that with appropriate angular settings, the higher orders of monochromator gratings can be significantly reduced.