PtyNAMi: ptychographic nano-analytical microscope

Ptychographic X-ray imaging at the highest spatial resolution requires an optimal experimental environment, providing a high coherent flux, excellent mechanical stability and a low background in the measured data. This requires, for example, a stable performance of all optical components along the entire beam path, high temperature stability, a robust sample and optics tracking system, and a scatter-free environment. This contribution summarizes the efforts along these lines to transform the nanoprobe station on beamline P06 (PETRA III) into the ptychographic nano-analytical microscope (PtyNAMi

Nanofocusing with aberration-corrected rotationally parabolic refractive X-ray lenses

Wavefront errors of rotationally parabolic refractive X-ray lenses made of beryllium (Be CRLs) have been recovered for various lens sets and X-ray beam configurations. Due to manufacturing via an embossing process, aberrations of individual lenses within the investigated ensemble are very similar. By deriving a mean single-lens deformation for the ensemble, aberrations of any arbitrary lens stack can be predicted from the ensemble with \bar{\sigma} = 0.034λ. Using these findings the expected focusing performance of current Be CRLs are modeled for relevant X-ray energies and bandwidths and it is shown that a correction of aberrations can be realised without prior lens characterization but simply based on the derived lens deformation. The performance of aberration-corrected Be CRLs is discussed and the applicability of aberration-correction demonstrated over wide X-ray energy ranges

High-Resolution and In-Solution Hard X-ray Ptychography at the Ptychographic Nano-Analytical Microscope PtyNAMi

X-ray microscopy is characterized by its high spatial resolution, exceeding that ofvisible light microscopy, while also being able to penetrate thick samples and sample enclosures that are inaccessible to electron microscopy. With these characteristics, x-ray microscopy excels in in-situ imaging of nanoscopic sample systems that are highly relevant in fields such as chemistry and life sciences.Ptychography is a lensless, computational microscopy technique in which the objective lens of the microscope is replaced with an algorithm to retrieve the phases of the coherent wave field. With this approach, the spatial resolution achieved in a ptychographic microscope can widely exceed that of the used x-ray focusing optics.One of the limiting factors of current ptychographic microscopes are nanopositioning errors and vibrations. Using laser-interferometry, these factors are studied in this thesis at the Ptychographic Nano-Analytical Microscope (PtyNAMi, P06, PETRA III) with particular attention to the occurring measurement uncertainties. In addition, an ultra-stable setup for two-dimensional measurements, that exhibits isotropic vibrations in the order of 1nm rms, is presented.Further improvement of the instrumentation is achieved by placing the area detector into a windowless and evacuated detector device, thereby suppressing the incoherent scattering background. With both of these instrumentational optimizations, ptychographic imaging with 10nm resolution is demonstrated.A distinct advantage of ptychography is the high degree of overdetermination in the data set that permits extensions of the ptychographic model to describe experimental imperfections. For samples that extent along the optical axis beyond the depth-offield of the microscope, several independent virtual object planes can be modeled, reconstructing all of them from a single measurement.This multi-slice ptychography is required when imaging the synthesis of nanoparticles in solution in cases in which the forming particles adhere to both windows of the in situ cell. Such an in situ cell, that is designed to be compatible with hard x-ray ptychographic imaging, is designed and commissioned.In a first demonstration, the nucleation and growth of copper and copper oxidenanoparticles in heated benzyl alcohol is imaged. For a period of 20 h, the growth of individual nanoparticles was imaged with a spatial resolution of 70nm and a temporal resolution of 22 minutes in two image planes. The observed imaging artifacts are part of an overarching discussion about the disadvantages of multi-slice ptychography

Soft X-ray grating monochromators as a source of spatial coherence degradation: A wave-optical approach

We present wave-optical simulations and a coherence analysis of the photon beam transported through a soft X-ray beamline, paying particular attention to a focusing varied line spacing (VLS) plane grating monochromator (PGM). We show that this beamline optical element used in several soft X-ray beamlines at synchrotron sources and free-electron lasers can cause a non-negligible spatial coherence degradation. We demonstrate that the origin of this effect arises from the coupling between spatial and spectral properties of the photon beam generated by the grating. The latter implies that space and frequency dependencies are not separable after such a dispersive element. It is shown which parameters are essential for this effect and how they are linked to each other

Multi-slice ptychography enables high-resolution measurements in extended chemical reactors

Ptychographic X-ray microscopy is an ideal tool to observe chemical processes under in situ conditions. Chemical reactors, however, are often thicker than the depth of field, limiting the lateral spatial resolution in projection images. To overcome this limit and reach higher lateral spatial resolution, wave propagation within the sample environment has to be taken into account. Here, we demonstrate this effect recording a ptychographic projection of copper(I) oxide nanocubes grown on two sides of a polyimide foil. Reconstructing the nanocubes using the conventional ptychographic model shows the limitation in the achieved resolution due to the thickness of the foil. Whereas, utilizing a multi-slice approach unambiguously separates two sharper reconstructions of nanocubes on both sides of the foil. Moreover, we illustrate how ptychographic multi-slice reconstructions are crucial for high-quality imaging of chemical processes by ex situ studying copper(I) oxide nanocubes grown on the walls of a liquid cell

A flexible ptychography platform to expand the potential of imaging at free electron lasers

Ptychography, a scanning coherent diffraction imaging method, can produce a high-resolution reconstruction of a sample and, at the same time, of the illuminating beam. The emergence of vacuum ultraviolet and X-ray free-electron lasers (FELs) has brought sources with unprecedented characteristics that enable X-ray ptychography with highly intense and ultra-fast short-wavelength pulses. However, the shot-to-shot pulse fluctuations typical for FEL pulses and particularly the partial spatial coherence of self-amplified spontaneous emission (SASE) FELs lead to numerical complexities in the ptychographic algorithms and ultimately restrict the application of ptychography at FELs. We present a general adaptive forward model for ptychography based on automatic differentiation, which is able to perform reconstructions even under these conditions. We applied this model to the first ptychography experiment at FLASH, the Free electron LASer in Hamburg, and obtained a high-resolution reconstruction of the sample as well as the complex wavefronts of individual FLASH pulses together with their coherence properties. This is not possible with more common ptychography algorithms

Quantitative characterization of aberrations in X-ray optics

Due to the weak interaction of X-rays with matter and their small wavelength on the atomic scale, stringent requirements are put on X-ray optics manufacturing and metrology. As a result, these optics often suffer from aberrations. Until now, X-ray optics were mainly characterized by their focal spot size and efficiency. How- ever, both measures provide only insufficient information about optics quality. Here, we present a quantitative analysis of residual aberrations in current beryllium compound refractive lenses using ptychography followed by a determination of the wavefront error and subsequent Zernike polynomial decomposition. Known from visible light optics, we show that these measures can provide an adequate tool to determine and compare the quality of various X-ray optics

Upscaling of multi-beam x-ray ptychography for efficient x-ray microscopy with high resolution and large field of view

Nondestructive imaging with both a large field of view and a high spatial resolution is crucial to understand complex materials and processes in science and technology. X-ray ptychography can provide highest spatial resolution but is limited in the field of view by the acquisition time and coherent flux at modern x-ray sources. By multi-beam ptychography, the sample can be imaged in parallel by several spatially separated and mutually incoherent beams. We have implemented this method using 3D nanoprinted x-ray optics to create tailor-made x-ray multi-beam arrays. The use of 3D printing allows us to create focusing optics with a minimum of nonfunctional support structures. In this way, large sample areas can be efficiently scanned in parallel with up to six illuminating beams

Upscaling of multi-beam x-ray ptychography for efficient x-ray microscopy with high resolution and large field of view

Nondestructive imaging with both a large field of view and a high spatial resolution is crucial to understand complex materials and processes in science and technology. X-ray ptychography can provide highest spatial resolution but is limited in the field of view by the acquisition time and coherent flux at modern x-ray sources. By multi-beam ptychography, the sample can be imaged in parallel by several spatially separated and mutually incoherent beams. We have implemented this method using 3D nanoprinted x-ray optics to create tailor-made x-ray multi-beam arrays. The use of 3D printing allows us to create focusing optics with a minimum of nonfunctional support structures. In this way, large sample areas can be efficiently scanned in parallel with up to six illuminating beams