Abstract
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° 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 here.
Highlights
At-wavelength metrology is a powerful and indispensable non-destructive tool for the development, characterization and final control of XUV-optical elements (Underwood & Gullikson, 1998; Gullikson et al, 2001; Tummler et al, 2003; Laubis et al, 2009)
Since the optical constants of the coating materials involved depend on wavelength, information on reflectivity or diffraction efficiency at a certain wavelength can be obtained only by this method and cannot be deduced from any other diagnostics results
Reflective zone plates (RZPs) are very attractive XUV dispersive and focusing optical elements for monochromators or XUV spectrometers, which have a high transmission and preserve the time structure of the radiation in the femtosecond range. Such RZP elements are developed at our institute (Erko et al, 2010) and the final characterization of their efficiency is performed with reflectometry
Summary
At-wavelength metrology is a powerful and indispensable non-destructive tool for the development, characterization and final control of XUV-optical elements (Underwood & Gullikson, 1998; Gullikson et al, 2001; Tummler et al, 2003; Laubis et al, 2009). The Helmholtz-Zentrum Berlin operates a grating technology project for the fabrication of high-precision laminar and blazed gratings (Loechel et al, 2013; Siewert et al, 2016) Within this project we have designed and fabricated a versatile UHV-reflectometer for the at-wavelength characterization of the in-house produced gratings, i.e. the determination of the diffraction efficiency in the wavelength range of interest. Apart from at-wavelength metrology for X-ray optical elements, reflectometry is a very powerful scientific technique It allows nondestructive characterization and depth-profiling of microstructures, layered systems and buried interlayers to be carried out (Filatova et al, 2009a,b). Performance data and first experimental results on multilayer gratings and on reflection zone plates are given
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