Heiner Lammert

The Nanometer Optical Component Measuring Machine: a new Sub‐nm Topography Measuring Device for X‐ray Optics at BESSY

The Nanometer Optical Component measuring Machine (NOM) has been developed at BESSY for the purpose of measuring the surface figure of optical components up to 1.2 m in length used at grazing incidence in Synchrotron Radiation beamlines. It is possible to acquire information about slope and height deviations and the radius of curvature of a sample in the form of line‐scans and in a three dimensional display format. With the NOM surfaces up to 600 cm2 have been measured with an estimated measuring uncertainty in the range of 0.01 arcsec rms and with a correspondingly high reproducibility. This is a five to tenfold improvement compared to the present state of the art of surface measuring techniques. The engineering conception, the design of the NOM and the first measurements are discussed in detail.

Finishing procedure for high-performance synchrotron optics

Modern synchrotron radiation sources of the 3rd generation like BESSY II, Spring-8 and others with their high brilliance beam characteristics need very high quality optics to exploit the full power of this radiation. For the grazing incidence reflecting type of that optics (flat, spherical or aspherical) besides roughness the slope deviation error is the most important spec, which has to be improved to meet the present and future performance requirements. Together with partners from industry we investigate and develop on the one hand surface figuring and polishing techniques for final finishing by using mainly ion beam milling technology and on the other hand we improve and make use of the combination of the surface shape measurements by means of interferometry, long trace and auto-collimation profilometry. We aim to achieve the following slope deviation errors on silicon optical elements: flat surface 310 mm long 0.03 arcsec rms, flat surface 100 mm long 0.02 arcsec rms and elliptical cylinder surface 210 mm long 0.1 arcsec rms. This is a five to ten-fold improvement compared to the present state of the art in production. To achieve the demanding specification it is necessary to measure and to deterministically machine the surface over a wide range of spatial wavelength down to the sub-millimeter range. In depth scale the sub-nanometer shape error level has to be achieved. The roughness of about 0.2 nm rms has not to be increased during the shape finishing.

Advanced metrology: an essential support for the surface finishing of high performance x-ray optics

The performance of x-ray beamlines at 3rd 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 cm2 have been measured with the NOM a measuring uncertainty in the range of 0.01 arcsec rms and a correspondingly high reproducibility [3]. 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.

Surface Deformations of Optical Elements — An Investigation of Optical Systems Using the BESSY‐NOM

The surface shape of optical elements is affected by their mounting (support, holder, clamping, cooling). The BESSY Nano Optic Measuring Machine (NOM) gives the opportunity to analyze these effects on the nanometer scale and sub‐nanometer scale. Linescans of surface profiles and the linescan‐based 3‐dimensional measurement feature of the NOM were used to characterize the surface shapes. In several configurations considering optical elements for the synchtrotron radiation application knowledge and effects about surface deformations due to mirror supports and coolings will be discussed. In this context a proposal for an adaptive mirror and the possible application in a BESSY‐beamline will be presented.

Six-strut arrangements for cartesian movements of mirrors

Abstract At BESSY a new six-strut arrangement for general small travel mirror adjustment mechanisms has been developed. This patented (Patent DE 10042802.5) arrangement allows very simple movements in all six linear and rotational degrees of freedom. The movements of the mirror are simply determined by moving either one drive, or up to three drives by the same amount. The first mirror adjustment systems of this design is successfully in operation since the start of BESSY II. Their performance and reliability is very satisfactory. This contribution will present the concepts.

Inspection of a Spherical Triple VLS‐Grating for Self‐Seeding of FLASH at DESY

To take benefit from the improved brilliance of the laser‐like source, proposed beamlines at Free Electron Lasers (FEL) require optical elements of excellent precision, characterised by slope errors beyond the state of the art limit of 0.5μrad rms for plane and spherical shape. Part of the monochromator beamline for self‐seeding at the vacuum‐ultraviolet Free Electron Laser (FLASH) at DESY is a triple Variable Line Spacing (VLS) grating of spherical shape. The three grating structures on a common substrate will cover the wavelength range from 6.4 to 60nm The challenging specifications of these grating structures are characterised by a slope error of less than 0.25μrad rms and very stringent parameters for the VLS‐polynomial. These grating structures have been measured by use of the Nano Optic Measuring Machine (NOM) at BESSY. Based on the principle of deflectometry the BESSY‐NOM represents the latest generation of slope measuring metrology instruments. The NOM enables the inspection of optical components ...

Synchrotron radiation mirror prototype made of monocrystalline tungsten

Synchrotron Radiation (SR) mirrors are ultra precision optical components with very high requirements to shape accuracy and smoothness. According to the special functions mirrors with different shapes are used. The dimensions of such mirrors extend from some tenfold of millimetres to a length of more than one meter. Commonly such mirrors are made of single crystal silicon, Zerodur(R), ULE(R) glass and in rare cases of silicon carbide, special steel or Glidcop(R). Some considerations lead to the result that also tungsten is an interesting alternative material for SR-mirrors. The paper presents the design, some results of the ultra precision machining and some functional parameters of the SR-mirror prototype.

Engineering aspects for the conception of the BESSY II beamlines

Abstract The very good results achieved at the first five undulator beamlines commissioned at BESSY II showed that thoroughly developed aspects for a general conception for the realization of new undulator beamlines for BESSY II have paid off. Basic ideas like an optical design with the possibility to employ optical elements with highest precision and simple drives combined with a very precise position control as well as an indispensable metrology laboratory of highest quality have been the key for success.