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

On the characterization of ultra precise X ray optical components advances and challenges in ex situ metrology

To fully exploit the ultimate source properties of the next generation light sources, such as free electron lasers FELs and diffraction limited storage rings DLSRs , the quality requirements for gratings and reflective synchrotron optics, especially mirrors, have significantly increased. These coherencepreserving optical components for high brightness sources will feature nanoscopic shape accuracies over macroscopic length scales up to 1000 mm. To enable high efficiency in terms of photon flux, such optics will be coated with application tailored single or multilayer coatings. Advanced thin film fabrication of today enables the synthesis of layers on the sub nanometre precision level over a deposition length of up to 1500 mm. Specifically dedicated metrology instrumentation of comparable accuracy has been developed to characterize such optical elements. Second generation slope measuring profilers like the nanometre optical component measuring machine NOM at the BESSY II Optics laboratory allow the inspection of up to 1500 mm long reflective optical components with an accuracy better than 50 nrad r.m.s. Besides measuring the shape on top of the coated mirror, it is of particular interest to characterize the internal material properties of the mirror coating, which is the domain of X rays. Layer thickness, density and interface roughness of single and multilayer coatings are investigated by means of X ray reflectometry. In this publication recent achievements in the field of slope measuring metrology are shown and the characterization of different types of mirror coating demonstrated. Furthermore, upcoming challenges to the inspection of ultra precise optical components designed to be used in future FEL and DLSR beamlines are discusse

Damage thresholds for blaze diffraction gratings and grazing incidence optics at an X ray free electron laser

Abstract The Linac Coherent Light Source LCLS is upgrading the machine to high repetition rate and to extended ranges. Novel coatings, with limited surface oxidation, which are able to work at the carbon edge, are required. In addition, high resolution soft X ray monochromators become necessary. One of the big challenges is to design the mirror geometry and the grating profile that have high reflectivity or efficiency and at the same time can survive the high peak energy of the FEL pulses. For these reasons, we investigated the experimental damage threshold, at 900 eV, of two platinum coated gratings with different blazed angles. The gratings were tested at 1o grazing incidence. To validate a model for which the damage threshold on blaze grating can be estimated by calculating the damage threshold of a mirror with an angle of incidence identical to the angle of incidence on the grating plus the blaze angle, tests on Pt coated substrates have also been performed. The results confirmed the prediction. We also investigated uncoated silicon, platinum and SiB3 both deposited on a silicon substrate . In general, the measured damage threshold at the grazing incidence is higher than calculated under the assumption that there is no energy transport from the volume where the photons are absorbed. However, we found that for the case of SiB3 coating, the grazing incidence condition did not increase the damage threshold indicating that the energy transport away from the extinction volume is negligibl

High precision tilt stage as a key element to a universal test mirror for characterization and calibration of slope measuring instruments

The ultimate performance of surface slope metrology instrumentation, such as long trace profilers and auto collimator based deflectometers, is limited by systematic errors that are increased when the entire angular range is used for metrology of significantly curved optics. At the ALS X Ray Optics Laboratory, in collaboration with the HZB BESSY II and PTB Germany metrology teams, we are working on a calibration method for deflectometers, based on a concept of a universal test mirror UTM [V. V. Yashchuk et al., Proc. SPIE 6704, 67040A 2007 ]. Potentially, the UTM method provides high performance calibration and accounts for peculiarities of the optics under test e.g., slope distribution and the experimental arrangement e.g., the distance between the sensor and the optic under test . At the same time, the UTM calibration method is inherently universal, applicable to a variety of optics and experimental arrangements. In this work, we present the results of tests with a key component of the UTM system, a custom high precision tilt stage, which has been recently developed in collaboration with Physik Instrumente, GmbH. The tests have demonstrated high performance of the stage and its capability after additional calibration to provide angular calibration of surface slope measuring profilers over the entire instrumental dynamic range with absolute accuracy better than 30 nrad. The details of the stage design and tests are presented.We also discuss the foundation of the UTM method and calibration algorithm, as well as the possible design of a full scale UTM syste