This PDF file contains the front matter associated with SPIE Proceedings Volume 6704, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

A new method for reducing the influence of vibrations in phase-shifting interferometry uses spatial information to achieve a 100X reduction in vibrationally induced surface distortion for small-amplitude vibrations. The technique does not require high density spatial carrier fringes and maintains full lateral sampling resolution. The principles of the technique are discussed and calculations highlight the capabilities, supported by real measurements under a variety of vibration conditions.

We present a full optimization of the high harmonics wave-front thanks to the use of a soft x-ray Hartmann sensor. The sensor was calibrated using high harmonics source with a λ/50 accuracy. We observed relatively good high harmonics wave-front, two times the diffraction-limit, with astigmatism as the dominant aberration for any interaction parameters. By slightly clipping the unfocused beam, it is possible to produce a diffraction-limited beam containing about 90% of the incident energy. The influence of high harmonic generation parameters was also studied in particularly the influence of the infra-red wave-front. In particular we studied the correlation between the infrared wave-front use to create high harmonics and the high harmonic wave-front. We also report wave-front measurements of a high order harmonic beam into an x-ray laser plasma amplifier at 32.8 nm.

Extremely high surface figure accuracy is required for hard x-ray nanofocusing mirrors to realize an ideal spherical wavefront in a reflected x-ray beam. We performed the figure correction of an elliptically figured mirror by a differential deposition technique on the basis of the wavefront phase error, which was calculated by a phase-retrieval method using only intensity profile on the focal plane. The measurements of the intensity profiles were performed at the 1-km-long beamline at SPring-8. The two measurements before and after the figure correction indicate that the beamwaist structure around the focal point is greatly improved.

A surface profiler system with a high accuracy of the order of nanometers has been developed for a half-meter-long X-ray mirror. This system is based on microstitching interferometer (MSI) and relative angle determinable stitching interferometer (RADSI). Using elastic hinges and linear actuators, we designed the 5-axis- and 6-axis stages for the MSI and RADSI, respectively, for the half-meter-long X-ray mirror. A test mirror of length 0.5 m was used to measure the height accuracy (1.4 nm in rms) and lateral resolution (36 μm) of the proposed system.

Fabrication and evaluation of elliptical X-ray mirrors, such as Kirkpatrick-Baez (K-B) mirrors produced by the profile-coating technique, requires accurate surface figure measurements over a wide range of spatial frequencies. Microstitching interferometry has proven to fulfill this requirement for length scales from a few μm up to the full mirror length. At the Advanced Photon Source, a state-of-the-art microroughness microscope interferometer that incorporates advanced microstitching capability has been used to obtain measurements of profile-coated elliptical K-B mirrors. The stitched surface height data provide previously unattainable resolution and reproducibility, which has facilitated the fabrication of ultrasmooth (< 1 nm rms residual height) profile-coated mirrors, whose hard X-ray focusing performance is expected to approach the diffraction limit. This paper describes the system capabilities and limitations. Results of measurements obtained with it will be discussed and compared with those obtained with the Long Trace Profiler.

Accurate and traceable angle measurement poses a central challenge to deflectometric profilometry. High-resolution electronic autocollimators are capable of providing accurate angle metrology for this purpose. The optimized calibration and the use of autocollimators under well-defined and stable measurement conditions are central to their proper application. To illustrate these issues, the autocollimator in use in the Extended Shear Angle Difference (ESAD) device for the absolute and traceable topography measurement of optical surfaces built at the Physikalisch-Technische Bundesanstalt (PTB) is considered. In contrast to other deflectometric profilers, ESAD combines deflectometric and shearing techniques in a unique way to minimize measurement errors and to optimize measurand traceability. Sub-nanometer repeatability, reproducibility, and uncertainty of the topography measurement are achieved for scans across near-flat surfaces up to 500 mm in diameter. In this paper, the ESAD shearing deflectometer and its measuring capabilities are presented. Information on the optimized use and accurate calibration of autocollimators for deflectometric applications is provided. The calibration of autocollimators by comparison with the highly accurate primary angle standard of PTB is illustrated. Factors influencing their angle response are discussed, such as the position of the aperture stop both along the autocollimator's optical axis and perpendicular to it.

The task of designing high performance X-ray optical systems requires the development of sophisticated X-ray scattering calculations based on rigorous information about the optics. One of the most insightful approaches to these calculations is based on the power spectral density (PSD) distribution of the surface height. The major problem of measurement of a PSD distribution with an interferometric and/or atomic force microscope arises due to the unknown Modulation Transfer Function (MTF) of the instruments. The MTF characterizes the perturbation of the PSD distribution at higher spatial frequencies. Here, we describe a new method and dedicated test surfaces for calibration of the MTF of a microscope. The method is based on use of a specially designed Binary Pseudo-random (BPR) grating. Comparison of a theoretically calculated PSD spectrum of a BPR grating with a spectrum measured with the grating provides the desired calibration of the instrumental MTF. The theoretical background of the method, as well as results of experimental investigations are presented.

The next generation of synchrotrons and free electron lasers require extremely high-performance x-ray optical systems for proper focusing. The necessary optics cannot be fabricated without the use of precise optical metrology instrumentation. In particular, the Long Trace Profiler (LTP) based on the pencil-beam interferometer is a valuable tool for low-spatial-frequency slope measurement with x-ray optics. The limitations of such a device are set by the amount of systematic errors and noise. A significant improvement of LTP performance was the addition of an optical reference channel, which allowed to partially account for systematic errors associated with wiggling and wobbling of the LTP carriage. However, the optical reference is affected by changing optical path length, non-homogenous optics, and air turbulence. In the present work, we experimentally investigate the questions related to the use of a precision tiltmeter as a reference channel. Dependence of the tiltmeter performance on horizontal acceleration, temperature drift, motion regime, and kinematical scheme of the translation stage has been investigated. It is shown that at an appropriate experimental arrangement, the tiltmeter provides a slope reference for the LTP system with accuracy on the level of 0.1 μrad (rms).

The development of third generation light sources like the Advanced Light Source (ALS) or BESSY II brought to a focus the need for high performance synchrotron optics with unprecedented tolerances for slope error and micro roughness. Proposed beam lines at Free Electron Lasers (FEL) require optical elements up to a length of one meter, characterized by a residual slope error in the range of 0.1 μrad (rms), and rms values of 0.1 nm for micro roughness. These optical elements must be inspected by highly accurate measuring instruments, providing a measurement uncertainty lower than the specified accuracy of the surface under test. It is essential that metrology devices in use at synchrotron laboratories be precisely characterized and calibrated to achieve this target. In this paper we discuss a proposal for a Universal Test Mirror (UTM) as a realization of a high performance calibration instrument. The instrument would provide an ideal calibration surface to replicate a redundant surface under test of redundant figure. The application of a sophisticated calibration instrument will allow the elimination of the majority of the systematic error from the error budget of an individual measurement of a particular optical element. We present the limitations of existing methods, initial UTM design considerations, possible calibration algorithms, and an estimation of the expected accuracy.

The first series of metrology round-robin measurements carried out in 2005 at the APS, ESRF and SPring-8 metrology laboratories involving two flat x-ray mirrors and a cylindrical x-ray mirror has shown excellent agreement among the three facilities' Long Trace Profilers (LTP) despite their architectural differences. Because of the growing interest in diffraction-limited hard x-ray K-B focusing mirrors, it was decided to extend the round robin measurements to spherical and aspheric x-ray mirrors. The strong surface slope variation of these mirrors presents a real challenge to LTP. As a result, new LTP measurement protocol has to be developed and implemented to ensure measurement accuracy and consistency. In this paper, different measurement techniques and procedures will be described, the results will be discussed, and comparison will be extended to micro-stitching interferometry measurements performed at Osaka University, Japan.

Long trace profilers (LTPs)⁽¹⁾ have been used at many synchrotron radiation laboratories worldwide for over a decade to measure surface slope profiles of long grazing incidence x-ray mirrors. Phase measuring interferometers (PMIs) of the Fizeau type, on the other hand, are being used by most mirror manufacturers to accomplish the same task. However, large mirrors whose dimensions exceed the aperture of the Fizeau interferometer require measurements to be carried out at grazing incidence, and aspheric optics require the use of a null lens. While an LTP provides a direct measurement of 1D slope profiles, PMIs measure area height profiles from which the slope can be obtained by a differentiation algorithm. Measurements of the two types of instruments have been found by us to be in good agreement, but to our knowledge there is no published work directly comparing the two instruments. This paper documents that comparison. We measured two different nominally flat mirrors with both the LTP in operation at the Advanced Photon Source (a type-II LTP) and a Fizeau-type PMI interferometer (Wyko model 6000). One mirror was 500 mm long and made of Zerodur, and the other mirror was 350 mm long and made of silicon. Slope error results with these instruments agree within nearly 100% (3.11±0.15 μrad for the LTP, and 3.11±0.02μrad for the Fizeau PMI interferometer) for the medium quality Zerodur mirror with 3 μrad rms nominal slope error. A significant difference was observed with the much higher quality silicon mirror. For the Si mirror, slope error data is 0.39±0.08Χrad from LTP measurements but it is 0.35 ± 0.01 μrad from PMI interferometer measurements. The standard deviations show that the Fizeau PMI interferometer has much better measurement repeatability.

A new ultra-precision profiler has been developed in order to measure such as asymmetric and aspheric profiles. In the present study, the normal vectors at each points on the surface are determined by the reflected light beam goes back exactly on the same path as the incident beam. The surface gradients at each point are calculated from the normal vector and the surface profile is obtained by integrating the gradient. The measuring instrument was designed according to the above principle of the measuring method. In the design, four ultra-precision goniometers were applied to the adjustment of the light axis for the normal vector measurement. In the measuring instrument, the angle-positioning resolution and accuracy of each goniometer are respectively 1.8x10^-8rad and 2x10^-7rad. A coaxial with an off-axis parabolic mirror has been developing for applying as an optical cavity. The most important engineering technique is to measure the profile of the reflective surface with sub nanometer. The present measuring instrument is evaluating to have capability to the surface measuring accuracy with nanometer for such parabolic mirror profile measurement. A coaxial off-axis parabolic mirror with 150 mm focal length has been polished. The outside and inside diameter of the mirror is 360 mm and 258 mm respectively. The thickness of the coaxial direction is 50 mm. The focal point is located on the center of the coaxial and the center of the coaxial direction of the mirror. The profile measurement such a mirror has been demonstrated. Specially, self calibration method for increasing the measured position accuracy from measured data is discussed.

In January 2007, Diamond Light Source (DLS) Ltd, the new 3rd generation national synchrotron source for the UK, welcomed its first scientific users. The successful exploitation of the intense synchrotron light produced by DLS will depend to a significant extent on the quality and performance of the optics employed in the experimental stations (beamlines). An in-house facility is required for acceptance and optimization of synchrotron optics, and for fundamental research to develop new technologies. A cleanroom laboratory has been constructed at DLS to house a suite of metrology instruments capable of characterizing state-of-the-art, synchrotron optics. A micro-interferometer and an atomic force microscope, with capability to integrate the two devices, are used to assess the atomic scale roughness of x-ray optics. A Fizeau interferometer and a slope measuring profiling system are used to measure the larger scale topography of sample surfaces. These non-contact, complementary techniques allow a broad spectrum of lateral features, from 1nm to 1m, to be probed to high accuracies. We present metrology data obtained using the instruments listed above.

Measurements taken in 2006 using Daresbury Laboratory's long trace profiler on the BESSY P1 'round robin' mirror highlighted a high level of background noise, believed to be principally from a combination of thermal and vibration sources. In addition, long-term thermal drifts within the instrument enclosure negated the benefit of multiple passes for averaging purposes. Further static stability tests on the LPT−V demonstrated noise levels on the slope measurement to be of the order of 0.5 μrad rms over an hour long period. We will demonstrate how the addition of a secondary instrument enclosure has reduced the background noise level in comparison tests to less than 0.1 μrad rms. We will detail the design of new granite supports for the translation beam and reference mirror, which are intended to minimise sources of vibration. Information will be provided regarding the replacement of the CCD detector/filter assembly and we will outline some proposed future developments.

Micro-focusing is widely applied at soft and hard x-ray wavelengths. One typical method, in addition to zone plates, is to split the focusing in the tangential and sagittal directions into two elliptically cylindrical reflecting elements, the so-called Kirkpatrick-Baez (KB) pair. In the simplest case each optic is made by grinding and polishing a flat, and applying unequal bending couples to each end. After briefly reviewing the nature of the bending, we show two new methods for optimal adjustment of these mirror systems using our surface normal slope measuring instrument, the long trace profiler (LTP). First, we adapt a method previously used to adjust mirrors on synchrotron radiation beamlines. We measure the slope of the surface before and after a single small adjustment of each bending couple. This permits an approximation to the functional dependence of slope on the adjustments, and allows, by applying the results of a simple matrix calculation, direct adjustment to a nearly final setting. Typically, the near linearity of the problem determines a very fast convergence of the adjustment procedure. Second, we subdivide the slope data from the LTP into three regions on the mirror, and fit a circle to each sub-region by regression. This method also allows rapid iterative adjustment of both bending couples. We show that this method is a particular case of the first one. As an overall indicator of predicted performance, we ray trace, using profiler data, predicting the exact optical performance to be expected during use of the system.

Systematic error in the Long Trace Profiler (LTP) has become the major error source as measurement accuracy enters the nanoradian and nanometer regime. Great efforts have been made to reduce the systematic error at a number of synchrotron radiation laboratories around the world. Generally, the LTP reference beam has to be tilted away from the optical axis in order to avoid fringe overlap between the sample and reference beams. However, a tilted reference beam will result in considerable systematic error due to optical system imperfections, which is difficult to correct. Six methods of implementing a non-tilted reference beam in the LTP are introduced: 1) application of an external precision angle device to measure and remove slide pitch error without a reference beam, 2) independent slide pitch test by use of not tilted reference beam, 3) non-tilted reference test combined with tilted sample, 4) penta-prism scanning mode without a reference beam correction, 5) non-tilted reference using a second optical head, and 6) alternate switching of data acquisition between the sample and reference beams. With a non-tilted reference method, the measurement accuracy can be improved significantly. Some measurement results are presented. Systematic error in the sample beam arm is not addressed in this paper and should be treated separately.

The next generation of synchrotrons and free electron lasers requires x-ray optical systems with extremely high-performance, generally, of diffraction limited quality. Fabrication and use of such optics requires highly accurate metrology. In the present paper, we discuss a way to improve the performance of the Long Trace Profiler (LTP), a slope measuring instrument widely used at synchrotron facilities to characterize x-ray optics at high-spatial-wavelengths from approximately 2 mm to 1 m. One of the major sources of LTP systematic error is the detector. For optimal functionality, the detector has to possess the smallest possible pixel size/spacing, a fast method of shuttering, and minimal nonuniformity of pixel-to-pixel photoresponse. While the first two requirements are determined by choice of detector, the non-uniformity of photoresponse of typical detectors such as CCD cameras is around 2-3%. We describe a flat-field calibration setup specially developed for calibration of CCD camera photo-response and dark current with an accuracy of better than 0.5%. Such accuracy is adequate for use of a camera as a detector for an LTP with performance of ~0.1 microradian (rms). We also present the design details of the calibration system and results of calibration of a DALSA CCD camera used for upgrading our LTP-II instrument at the ALS Optical Metrology Laboratory.