The Göttingen Instrument for Nano-Imaging with X-ray (GINIX) is a holography endstation located at the P10 coherence beamline at PETRA III, designed and operated by the University of Göttingen in close collaboration with DESY Photon science Hamburg [1-2]. GINIX is designed as a waveguide based holography experiment with a Kirkpatrick-Baez nanofocus. Its versatility has stimulated a great manifold of imaging modalities. Today, users choose the GINIX setup not only for its few nm coherent waveguide beams (e.g. for ptychography or holography), but also to carry out scanning SAXS measurements to probe local anisotropies with sub-micron real-space and even higher reciprocal space resolution. In addition, it is possible to combine different detectors for e.g. simultaneous SAXS/WAXS and fluorescence measurements . We summarise our ongoing efforts to reduce vibrations in the setup, and present latest experimental results obtained with GINIX, focusing on the unique capabilities offered by its versatile and flexible design. The overview includes results from different imaging schemes such as waveguide based zoom-tomography and user examples in WAXS geometry. We show how to correlate complementary techniques like holography and scanning SAXS and present first results obtained using a new fast sample scanner for Multilayer Zone Plate imaging..
Hard x-ray imaging methods are routinely used in two and three spatial dimensions to tackle challenging scientific questions of the 21st century, e.g. catalytic processes in energy research and bio-physical experiments on the single-cell level [1–3]. Among the most important experimental techniques are scanning SAXS to probe the local orientation of filaments and fluorescence mapping to quantify the local composition. The routinely available spot size has been reduced to few tens of nanometres; but the real-space resolution of these techniques can degrade by (i) vibration or drift, and (ii) spreading of beam damage, especially for soft condensed matter on small length scales. We have recently developed new Multilayer Zone Plate (MZP) optics for focusing hard (14 keV) and very hard (60 keV to above 100 keV) x-rays down to spot sizes presumably on 5 or 10nm scale. Here we report on recent progress on a new MZP based sample scanner, and how to tackle beam damage spread. The Eiger detector synchronized to a piezo scanner enables to scan in a 2D continuous mode fields of view larger than 20μm squared, or for high resolution down to (virtual) pixel sizes of below 2nm, in about three minutes for 255×255 points (90 seconds after further improvements). Nano-SAXS measurements with more than one million real-space pixels, each containing a full diffraction image, can be carried out in less than one hour, as we have shown using a Siemens star test pattern.
Penetration lengths in the millimetre range make hard x-rays above 60 keV a well-suited tool for non-invasive probing of small specimens buried deep inside their surroundings, and enable studying individual components inside assembled, complex devices (solar cells, batteries etc.). The real-space resolution of typical imaging modalities like fluorescence mapping, scanning SAXS and WAXS depend on the available beam size. Although routine in the 5–25keV regime [1-4], spot sizes below 50nm are very challenging at x-ray energies above 50 keV: Compound refractive lenses lack in refractive power, the multilayer thickness of coated mirrors is bounded by interfacial diffusion, and lithographic Fresnel Zone Plates loose their efficiency in the two-digit keV regime. Multilayer Laue Lenses and Multilayer Zone Plates (MZP) are promising candidates for high-keV focusing to small spot sizes; compared to Fresnel Zone Plates, the aspect ratio comparing outermost layer width (~focal spot size) to optical thickness (efficiency) is virtually unlimited by the fabrication. Using Pulsed Laser Deposition on a rotating wire (several millimetre long), we have fabricated an MZP with 10nm outermost zone widths and optical thickness of 30 μm(optimum phase shift at 60 keV), yielding an unprecedented ultra-high aspect ratio of 1:3000 (outermost zone width compared to optical thickness). We present experimental results obtained at ESRF’s high energy beamline ID31, where for the first time scanning experiments with real-space resolutions below 50nm even at x-ray energies ranging from 60 keV to above 100 keV have been achieved.
Hard x-ray beams can be focused using refractive lenses, but depending on energy, a large number N of individual lenses stacked in a row is needed. Such a stack can be either composed of single lenses in cartridges, or lithographically fabricated lenses in a row. With N in the three-digit regime, the question arises which tolerances on lens alignment and shape have to be met not to disturb the focus. Here we use analytical and numerical calculations based on a Zernike polynomial expansion to give such error bounds for typical set-ups.
Hard x-ray focusing and imaging on the few nano metre scale has gained a lot of attraction in the last couple of years. Thanks to new developments in fabrication and inspection of high-N.A. optics, focusing of hard x-rays has caught up with the focusing performance for soft x-rays. Here we review the latest imaging experiments of the Göttinger Multilayer zone plate collaboration, summarising our route from 1D to 2D lenses for different hard x-ray energies, and recapitulate recent progress on a journey from focusing to imaging.
Efficient focusing optics are a key ingredient for high-resolution (few nanometer) hard x-ray imaging. In recent years, a combined optical scheme using prefocusing to match the coherent fraction of the synchrotron’s x-ray beam to a high-resolution multilayer zone plate (MZP) has been presented. This scheme allows sub-5 nm focusing of hard x-rays in two dimensions. Nevertheless, the first lenses prepared by pulsed laser deposition of alternating WW and Si layers were limited by a low deposition rate of W and the formation of lots of Si-droplets during film growth. Thus, the material combination has been changed to Ta<sub>2</sub>O<sub>5</sub> and ZrO<sub>2</sub>, allowing a much faster and more accurate layer growth. Here we present latest developments achieved in both design and fabrication of high-resolution MMZPs: A MZP with a lens diameters of about 15 micrometers, sharp layer interfaces, 5 nm outermost zone widths and a focal length of 0.5 mm. Too increase the focusing efficiency even more, a tilted geometry using a pulled glass fibre was successfully implemented.
We present experiments carried out using a combined hard x-ray focusing set-up preserving the benefits of a large-aperture Kirckpatrick-Baez (KB) mirror system and a small focal length multilayer zone plane (MZP). The high gain KB mirrors produce a pre-focus of 400 nm × 200 nm; in their defocus, two MZP lenses of diameter of 1.6 μm and 3.7 μm have been placed, with focal lengths of 50 μm and 250 μm respectively. The lenses have been produced using pulsed laser deposition (PLD) and focused ion beam (FIB). Forward simulations including error models based on measured deviations, auto-correlation analysis and three-plane phase reconstruction support two-dimensional focus sizes of 4.3 nm × 4.7 nm (7:9 keV, W/Si)<sup>1</sup> and 4.3 nm ×5.9 nm (13:8 keV, W/ZrO<sub>2</sub>), respectively.
Recently, a new software tool was developed at the ESRF that can perform wave optical simulations on curved
multilayer optics. It is based on a Takagi-Taupin approach and the two beam approximation. Outside the multilayer
structure the beam is propagated by phase ray tracing and by solving the Kirchhoff integral. Extended sources can be
modelled by superposition of point sources. The spatial coherence can be varied by the degree of random averaging of amplitude and phase of these point sources and by their distribution in space. This work deals with applications of this formalism to realistic cases of existing or planned multilayer based nanofocusing mirrors. It also attempts to explore fundamental physical limitations and how they are reproduced by the model. Open questions will be addressed and potential future investigations will be outlined.
Penetration, micro-resolution, and scattering were the keywords of x-ray analyses in the 20th century. Over the last 15
years, a great class of coherent imaging techniques has emerged as new tools, allowing for low-dose imaging of biological
specimen on the nanoscale.
Apart from experimental and technical challenges, a better understanding of partially coherent beam propagation is the
key for exploiting the new methods' full performance. We present a simulation framework to calculate the mutual intensity
and the degree of spatial coherence of typical x-ray focusing and filtering devices used at 3rd generation synchrotron
We propose the following modeling scheme: A set of independent point-sources yield independent basic fields, which
are superposed in a stochastic manner; by taking the ensemble average, both partially coherent intensity and degree of
coherence can be obtained from the mutual intensity. By including real structure effects, like height deviations of focusing
mirrors, and vibration of optical components, advanced predictions of x-ray beams can be made. This knowledge is
expected to improve reconstruction results from coherent imaging experiments.
Coherence simulations of focusing mirrors are presented and validated with analytical results as well as with experimental
tests. Coherence filtering by use of x-ray waveguides is shown numerically. We also present first simulations for
partially coherent focusing by compound refractive lenses.
The degradation mechanisms are a critical issue if multilayers are used as monochromators for white beam synchrotron
applications. To quantify the radiation impact x-ray reflectivity measurements before, during, and after white beam
exposure were performed.
For the in-situ irradiation study a versatile vacuum chamber was developed and tested using a high power undulator
source. The device is equipped with a cooling system for the multilayer samples to distinguish thermal effects from pure
radiation induced ones. The x-ray reflectivity was measured at fixed angle of incidence in an energy dispersive mode and
as a function of time. The energy dispersive detection allows for the simultaneous observation of the multilayer
reflectivity spectrum over a wide range. The white beam study includes various long-term exposures with an incoming
load up to 250 W.
Ex-situ x-ray reflectivity measurements and beam imaging were carried out with monochromatic radiation at 8 keV
before and after the white beam exposure. TEM analysis provides complementary information on the layer structure in
Depending on the material system, the total radiation dose, and the sample environment, different degrees of
modifications in the multilayer structure were observed.