The performance of x-ray beamlines at 3<sup>rd</sup> generation synchrotron radiation sources and Free Electron Lasers (FELs) is limited by the quality of the state of the art optical elements. Proposed FEL beamlines require optical components which are of better quality than is available from the optical manufacturing technology of today. As a result of a joint research project (Nanometer Optik Komponenten - NOK) coordinated by BESSY, involving both metrologists and manufacturers it is possible now to manufacture optical components beyond the former limit of 0.1 arcsec rms slope error [1, 2]. To achieve the surface finishing of optical components with a slope error in the range of 0.04 arcsec rms (for flat or spherical surfaces up to 300 mm in length) by polishing and finally by ion beam figuring technology it is essential that the optical surface be mapped and the mapping data used as input for the multiple ion beam figuring stages. Metrology tools of at least five times superior accuracy to that required of the component have been developed in the course of the project. The Nanometer Optical Component measuring Machine (NOM) was developed at BESSY for line and area measurements of the figure of optical components used at grazing incidence in synchrotron radiation beamlines. Surfaces up to 730 cm<sup>2</sup> have been measured with the NOM a measuring uncertainty in the range of 0.01 arcsec rms and a correspondingly high reproducibility . Three dimensional measurements were used to correct polishing errors some nanometers high and only millimeters in lateral size by ion beam treatment. The design of the NOM, measurement results and results of NOM supported surface finishing by ion beam figuring will be discussed in detail. The improvement of beamline performance by the use of such high quality optical elements is demonstrated.
The technological limit on the beam quality when modern synchrotron radiation sources are used is determined by the geometrical accuracy of the optical components. This in turn is limited by the accuracy of the measuring technique which is within the range of up to 0.05 arcsec rms for one meter mirror length, which corresponds (in the absence of waviness) to an uncertainty of the topography of 5 nm rms. If the topography can be measured with higher accuracy, modern methods of ion beam processing allow the surface to be postprocessed with a high resolution of depth. We will present first tests with a novel measuring device which allows deflectometric measurements by the ESAD principle (Extended Shear Angle Difference) to be carried out. The basic item of this device is a commercial electronic autocollimator (AC) whose exit aperture is tripartite. By suitable evaluation one is in consequence able to simultaneously determine the angle information belonging to three surface points situated next to one another. According to the ESAD method, the angular topography can be completely reconstructed from two sets of angular difference data. The uncertainty of measurements of angular difference is transferred with a factor close to 1 to that of the set of reconstructed angle. First measurements show a reproducibility of about 25 milli-arcsec rms at a time of integration of 0.4 seconds per point. With this set-up, in the first order, no guide errors, vibrations or air turbulences enter.
A coaxial carbon-dioxide waveguide laser with rf excitation at 96.5 MHz and an output power exceeding 1.3 kW is described. This laser uses a new concept of electrode segmentation for discharge homogenization in addition to a new kind of optical resonator for the coaxial geometry called the toothed mirror resonator.
Calculations of the waveguide mode coupling losses due to free space propagation between the waveguide endings and the resonator mirrors of a coaxial Cu-waveguide are presented. The results show that the mode coupling losses have a strong influence on the mode selection in a coaxial waveguide laser.