The focusing efficiency of binary Fresnel zone plate lenses is fundamentally limited and higher efficiency requires a
multi step lens profile. To overcome the manufacturing problems of high resolution and high efficiency multistep zone
plates, we investigate the concept of stacking two different binary zone plates in each other’s optical near-field. We use a
coarse zone plate with π phase shift and a double density fine zone plate with π/2 phase shift to produce an effective 4-
step profile. Using a compact experimental setup with piezo actuators for alignment, we demonstrated 47.1% focusing
efficiency at 6.5 keV using a pair of 500 μm diameter and 200 nm smallest zone width. Furthermore, we present a
spatially resolved characterization method using multiple diffraction orders to identify manufacturing errors, alignment
errors and pattern distortions and their effect on diffraction efficiency.
The Nanoscopium 155 m-long scanning nanoprobe beamline of Synchrotron Soleil (St Aubin, France) is dedicated to
quantitative multi-modal imaging. Dedicated experimental stations, working in consecutive operation mode, will provide
coherent scatter imaging and spectro-microscopy techniques in the 5-20 keV energy range for various user communities.
Next to fast scanning, cryogenic cooling will reduce the radiation damage of sensitive samples during the measurements.
Nanoscopium is in the construction phase, the first user experiments are expected in 2014. The main characteristics of
the beamline and an overview of its status are given in this contribution.
The design and implementation of a pair of 100 mm-long grazing-incidence total-reflection mirrors for the hard
X-ray beamline Nanoscopium at Synchrotron Soleil is presented. A vertically and horizontally nanofocusing
mirror pair, oriented in Kirkpatrick-Baez geometry, has been designed and fabricated with the aim of creating a
diffraction-limited high-intensity 5 − 20 keV beam with a focal spot size as small as 50 nm. We describe the design
considerations, including wave-optical calculations of figures-of-merit that are relevant for spectromicroscopy,
such as the focal spot size, depth of field and integrated intensity. The mechanical positioning tolerance in the
pitch angle that is required to avoid introducing high-intensity features in the neighborhood of the focal spot
is demonstrated with simulations to be of the order of microradians, becoming tighter for shorter focal lengths
and therefore directly affecting all nanoprobe mirror systems. Metrology results for the completed mirrors are
presented, showing that better than 1.5 °A-rms figure error has been achieved over the full mirror lengths with
respect to the designed elliptical surfaces, with less than 60 nrad-rms slope errors.
Recent advances in the fabrication of diffractive X-ray optics have boosted hard X-ray microscopy into spatial
resolutions of 30 nm and below. Here, we demonstrate the fabrication of zone-doubled Fresnel zone plates for
multi-keV photon energies (4-12 keV) with outermost zone widths down to 20 nm. However, the characterization
of such elements is not straightforward using conventional methods such as knife edge scans on well-characterized
test objects. To overcome this limitation, we have used ptychographic coherent diffractive imaging to characterize
a 20 nm-wide X-ray focus produced by a zone-doubled Fresnel zone plate at a photon energy of 6.2 keV. An
ordinary scanning transmission X-ray microscope was modified to acquire the ptychographic data from a strongly
scattering test object. The ptychographic algorithms allowed for the reconstruction of the image of the test
object as well as for the reconstruction of the focused hard X-ray beam waist, with high spatial resolution and
dynamic range. This method yields a full description of the focusing performance of the Fresnel zone plate
and we demonstrate the usefulness ptychographic coherent diffractive imaging for metrology and alignment of
nanofocusing diffractive X-ray lenses.
Refractive X-ray lenses can be used effectively, to focus or collimate X-rays with photon energies clearly above 10 keV.
On the one hand parabolic Compound Refractive Lenses (CRLs) are suitable as imaging optics in high resolution X-ray
microscopy. The most recent developments are nanofocusing refractive X-ray lenses (NFLs). These show focal spot
sizes of less below 100 nm. On the other hand refractive X-ray lenses can provide a high photon flux when used as large
aperture condenser optics. Two types of refractive condenser optics made out of structures with triangular profile have
been developed at the Institute for Microstructure Technology (IMT) at the Karlsruhe Institute of Technology (KIT) and
have been tested at synchrotron sources in recent years. One type of special interest is the Rolled X-ray Prism Lens
(RXPL). These lenses are made of a rolled polymer foil structured with micro grooves with triangular profile. The
combination of such condenser optics and NFLs provides a basis for future hard X-ray microscopes.
New developments in X-ray instrumentation and analysis have facilitated the development and improvement
of various scanning X-ray microscopy techniques. In this contribution, we offer an overview of recent scanning
hard X-ray microscopy measurements performed at the Swiss Light Source. We discuss scanning transmission
X-ray microscopy in its transmission, phase contrast, and dark-field imaging modalities. We demonstrate how
small-angle X-ray scattering analysis techniques can be used to yield additional information. If the illumination
is coherent, coherent diffraction imaging techniques can be brought to bear. We discuss how, from scanning
microscopy measurements, detailed measurements of the X-ray scattering distributions can be used to extract
high-resolution images. These microscopy techniques with their respective imaging power can easily be combined
to multimodal X-ray microscopy.
Extracting quantitative image information from coherent diffraction measurements remains challenging due to
problems such as slow convergence of iterative phase retrieval algorithms, questionable uniqueness of the resulting
images, and common requirements of compactness of the specimens. These difficulties are overcome by combining
iterative phase retrieval with ptychography, i.e., the use of multiple diffraction measurements probing several
overlapping regions of the specimen. While promising results of ptychographical coherent diffractive imaging have
been achieved the technique has been limited by requiring precise knowledge of the illumination. We present
advances of the reconstruction algorithm, which allow unsupervised deconvolution of the illuminating probe and
the complex-valued optical transmission function of the specimen. We have performed measurements using both
visible light and x-rays, demonstrating sub-50nm resolution.
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.
We report our progress in the growth of periodic and depth-graded multilayers in the APS rotary deposition system, a
machine designed for fabrication of films tens of microns thick with thousands of layers. A computational method was
employed to design depth-graded multilayers for use as wide-angular bandpass reflective optics. We present
experimental results for a 154-layer WSi<sub>2</sub>/Si multilayer system with bilayer thickness ranging from 2.2 nm to 5.5 nm that
closely match theoretical flat-top reflectivity predictions of 9.8% from 15.6 mrad to 23.3 mrad at 8 keV.
Compound refractive lenses (CRLs) are arrays of concave lenslets used to focus X-rays. For a given incident X-ray
beam energy, the focal length of a CRL depends on the material and shape of the individual lenslets, and in particular is
inversely related to the number of lenslets in the array. The throughput of a lens array is heavily affected by absorption
of the X-rays in the lens. For this reason, it is necessary to employ low-atomic-number materials and fabricate the
lenses as thin as possible, especially for low to moderate X-ray energy range (~ 5 - 20 keV) photons.
Lithium and beryllium are two of the best candidate materials for X-ray lenses due to their relatively high (real
decrement) index of refraction and low X-ray absorption. Lithium is very malleable, however, and reacts strongly with
moisture in the air, requiring a special fabrication environment and housing. Beryllium, on the other hand, is a solid
metal and is easy to machine and handle.
This paper summarizes the recent work at the Advanced Photon Source (APS) on parabolic lithium and cylindrical
beryllium lenses. These lenses have been tested on APS X-ray beamlines. Their performance in terms of the focal size
and gain is described and further improvements including tighter manufacturing tolerances and thinner lens walls are