The at wavelength metrology facility for UV and XUV reflection and diffraction optics at BESSY II

A technology center for the production of high precision reflection gratings has been established. Within this project a new optics beamline and a versatile reflectometer for at wavelength characterization of UV and XUV reflection gratings and other nano optical elements has been set up at BESSY II. The Plane Grating Monochromator beamline operated in collimated light c PGM is equipped with an SX700 monochromator, of which the blazed gratings 600 and 1200 lines mm 1 have been recently exchanged for new ones of improved performance produced in house. Over the operating range from 10 to 2000 eV this beamline has very high spectral purity achieved by i a four mirror arrangement of different coatings which can be inserted into the beam at different angles and ii by absorber filters for high order suppression. Stray light and scattered radiation is removed efficiently by double sets of in situ exchangeable apertures and slits. By use of in and off plane bending magnet radiation the beamline can be adjusted to either linear or elliptical polarization. One of the main features of a novel 11 axes reflectometer is the possibility to incorporate real life sized gratings. The samples are adjustable within six degrees of freedom by a newly developed UHV tripod system carrying a load up to 4 kg, and the reflectivity can be measured between 0 and 90 deg incidence angle for both s and p polarization geometry. This novel powerful metrology facility has gone into operation recently and is now open for external users. First results on optical performance and measurements on multilayer gratings will be presented her

Gratings for synchrotron and FEL beamlines a project for the manufacture of ultra precise gratings at Helmholtz Zentrum Berlin

Blazed gratings are of dedicated interest for the monochromatization of synchrotron radiation when a high photon flux is required, such as, for example, in resonant inelastic X ray scattering experiments or when the use of laminar gratings is excluded due to too high flux densities and expected damage, for example at free electron laser beamlines. Their availability became a bottleneck since the decommissioning of the grating manufacture facility at Carl Zeiss in Oberkochen. To resolve this situation a new technological laboratory was established at the Helmholtz Zentrum Berlin, including instrumentation from Carl Zeiss. Besides the upgraded ZEISS equipment, an advanced grating production line has been developed, including a new ultra precise ruling machine, ion etching technology as well as laser interference lithography. While the old ZEISS ruling machine GTM 6 allows ruling for a grating length up to 170 mm, the new GTM 24 will have the capacity for 600 mm 24 inch gratings with groove densities between 50 lines mm 1 and 1200 lines mm 1. A new ion etching machine with a scanning radiofrequency excited ion beam HF source allows gratings to be etched into substrates of up to 500 mm length. For a final at wavelength characterization, a new reflectometer at a new Optics beamline at the BESSY II storage ring is under operation. This paper reports on the status of the grating fabrication, the measured quality of fabricated items by ex situ and in situ metrology, and future development goal

Stripe pattern in the intensity profile of collimated soft x ray beams caused by surface corrugation of the refocusing mirrors

The effect of progress in surface finishing of optical components on the collimated beam properties of soft x ray beamlines at synchrotron radiation facilities is demonstrated a stripe pattern, experimentally observed in the 2D intensity profile of beamlines with optical components manufactured 10 15 years ago, would be strongly attenuated if the existing refocusing mirror was replaced by an ultra precise mirror manufactured with state of the art of today surface finishing techniques. The observed stripe pattern is not caused by diffraction because its period length did not change with photon energy. Instead it can be explained with geometrical optics and is due to the height profile of the refocusing mirror which has been independently measured with a long trace profiler and used as an input in our raytracing simulation

Investigations on the spatial resolution of autocollimator based slope measuring profilers

During the last decade, autocollimator based slope measuring profilers like the Nanometer Optical Component Measuring Machine NOM at BESSY II have become standard instrument for the ultraprecise characterization of synchrotron optics with nanometer accuracy. Due to the increasing demand for highest accuracy, which can be provided by these profilers, further investigations are necessary to understand the performance of these instruments. Besides the achievable accuracy, it is of particular interest to characterize the possible spatial resolution of such instrumentation. The performance of the BESSY NOM was characterized by means of sinusoidal and chirped surface profiles. A dedicated sample was prepared using the Atmospheric Plasma Jet Machining technology at the IOM Leibniz Institut for Oberflaechenmodifizierung e.V. We report on our tests on the NOM, the interferometer measurements done for comparison as well as the sample preparatio

New UHV angle encoder for high resolution monochromators, a modern spare part for the Heidenhain UHV RON 905

There are a large number of soft X ray grating monochromators for high resolution synchrotron radiation experiments in operation worldwide. At BESSY II eighteen of the monochromators currently in use are equipped with Heidenhain UHV RON905 angle encoders. Those angle encoders have successfully been in operation for decades. Today, this type of encoder has become a legacy product and repairs are getting expensive. Therefore, we have developed a new angle encoder, a mechanically compatible drop in replacement of the RON905. A mechanically fitting prototype, based on RENISHAW absolute encoders, was tested on a high precision angle drive test bench. Fourier analysis of the encoder data allowed us to determine the precision for different angle ranges and indicates a better precision for the new angle encoder. Furthermore, we will introduce an on line, in situ method using electron absorption spectroscopy to improve system accuracy with plane grating monochromators in collimated light using the newly developed encode

Linear chirped slope profile for spatial calibration in slope measuring deflectometry.

Slope measuring deflectometry is commonly used by the X-ray optics community to measure the long-spatial-wavelength surface figure error of optical components dedicated to guide and focus X-rays under grazing incidence condition at synchrotron and free electron laser beamlines. The best performing instruments of this kind are capable of absolute accuracy on the level of 30-50 nrad. However, the exact bandwidth of the measurements, determined at the higher spatial frequencies by the instrument's spatial resolution, or more generally by the instrument's modulation transfer function (MTF) is hard to determine. An MTF calibration method based on application of a test surface with a one-dimensional (1D) chirped height profile of constant amplitude was suggested in the past. In this work, we propose a new approach to designing the test surfaces with a 2D-chirped topography, specially optimized for MTF characterization of slope measuring instruments. The design of the developed MTF test samples based on the proposed linear chirped slope profiles (LCSPs) is free of the major drawback of the 1D chirped height profiles, where in the slope domain, the amplitude strongly increases with the local spatial frequency of the profile. We provide the details of fabrication of the LCSP samples. The results of first application of the developed test samples to measure the spatial resolution of the BESSY-NOM at different experimental arrangements are also presented and discussed