As a coherent diffraction imaging technique, ptychography provides high-spatial resolution beyond Rayleigh's criterion of the focusing optics, but it is also sensitively affected by the decoherence coming from the spatial and temporal variations in the experiment. Here we show that high-speed ptychographic data acquisition with short exposure can effectively reduce the impact from experimental variations. To reach a cumulative dose required for a given resolution, we further demonstrate that a continuous multi-pass scan via high-speed ptychography can achieve high-resolution imaging. This low-dose scan strategy is shown to be more dose-efficient, and has potential for radiation-sensitive sample studies and time-resolved imaging.

X-ray ptychography, a powerful scanning lensless imaging technique, has become attractive for nondestructively imaging internal structures at nanoscale. Stage positioning overhead in conventional step-scan ptychography is one of the limiting factors on the imaging throughput. In this work, we demonstrate the use of advanced fly scan ptychography to achieve high-resolution ptychograms of modern integrated circuits on a large field-of-view at millimeter scale. By completely removing stage overheads between scan points, the imaging time for millimeter-size sample can be significantly reduced. Furthermore, we implement the orthogonal probe relaxation technique to overcome the variation of illumination across the large scan area as well as local vibrations. The capability of x-ray ptychography shown here is broadly applicable for various studies, which requires both high spatial resolution and large scan area.

Ptychography is a rapidly developing scanning microscopy which is able to view the internal structures of samples at a high resolution beyond the illumination size. The achieved spatial resolution is theoretically dose-limited. A broadband source can provide much higher flux compared with a monochromatic source; however, it conflicts with the necessary coherence requirements of this coherent diffraction imaging technique. In this paper, a multi-wavelength reconstruction algorithm has been developed to deal with the broad bandwidth in ptychography. Compared with the latest development of mixed-state reconstruction approach, this multi-wavelength approach is more accurate in the physical model, and also considers the spot size variation as a function of energy due to the chromatic focusing optics. Therefore, this method has been proved in both simulation and experiment to significantly improve the reconstruction when the source bandwidth, illumination size and scan step size increase. It is worth mentioning that the accurate and detailed information of the energy spectrum for the incident beam is not required in advance for the proposed method. Further, we combine multi-wavelength and mixed-state approaches to jointly solve temporal and spatial partial coherence in ptychography so that it can handle various disadvantageous experimental effects. The significant relaxation in coherence requirements by our approaches allows the use of high-flux broadband X-ray sources for high-efficient and high-resolution ptychographic imaging.

We will present the design for the In-Situ Nanoprobe (ISN) beamline that is being developed as part of the Upgrade of the APS storage ring with an MBA magnetic lattice. The ISN will provide large working distance of 60 mm for in-situ and operando environments, and a small spot of 20 nm (25 keV) for imaging materials with small defects and functional components. To achieve both long working distance and small spot size, Kirkpatrick-Baez mirrors will be used as nanofocusing optics. The major contrast mechanisms will be XRF imaging for chemical characterization ptychography for transmission imaging with sub-10 nm resolution. Auxiliary diffraction capabilities will allow monitoring of phase change during in-situ studies. To achieve the demagnification required to achieve small spot sizes, the ISN instrument will be placed at a distance of 220 m from the x-ray source, in a satellite building outside the APS storage ring. The ISN will provide hard x-rays with photon energy between 4.8 keV and 30 keV, enabling access to the absorption edges of to most elements in the periodic system. The MBA lattice and insertion devices, coupled with the high reflectivity of the K-B mirror system, provide a very high coherent flux of above 4*1012 Ph/s at 5 keV, and 6*1012 Ph/s at 30 keV. This allows hierarchical imaging of large samples with very small spot size, as well as multidimensional imaging, such as 3D imaging and temperature change, or 2D imaging with change of several environmental parameters. The ISN will provide flow of fluids, gases, and variable temperature.

X-ray ptychography has gained tremendous success in providing quantitative high-resolution imaging for extended samples. Here we report on recent developments in ptychography imaging techniques and the improvement of reconstruction methods to increase ptychographic imaging throughput at the Advanced Photon Source.

Ptychography has revolutionized coherent X-ray microscopy and became a mainstream technique for high-resolution imaging. Combined with conventional methods such as tomography and laminography, the technique has been successfully extended to 3D imaging, with state-of-the-art beamlines reaching below 20 nm spatial resolution [1,2], further providing new opportunities for characterizing materials such as integrated circuits (IC) and biological specimens. Moreover, the scanning sample scheme allows ptychography to be easily scaled to large objects at millimeter and even centimeter-scale.

X-ray ptychography is a rapidly developing coherent diffraction imaging technique that provides nanoscale resolution on extended field-of-view. However, the requirement of coherence and the scanning mechanism limit the throughput of ptychographic imaging. In this paper, we propose X-ray ptychography using multiple illuminations instead of single illumination in conventional ptychography. Multiple locations of the sample are simultaneously imaged by spatially separated X-ray beams, therefore, the obtained field-of-view in one scan can be enlarged by a factor equal to the number of illuminations. We have demonstrated this technique experimentally using two X-ray beams focused by a house-made Fresnel zone plate array. Two areas of the object and corresponding double illuminations were successfully reconstructed from diffraction patterns acquired in one scan, with image quality similar with those obtained by conventional single-beam ptychography in sequence. Multi-beam ptychography approach increases the imaging speed, providing an efficient way for high-resolution imaging of large extended specimens.

As a scanning version of coherent diffraction imaging (CDI), X-ray ptychography has become a popular and very successful method for high-resolution quantitative imaging of extended specimens. The requirements of mostly coherent illumination and the scanning mechanism limit the throughput of ptychographic imaging. In this paper, we will introduce the methods we use at the Advanced Photon Source (APS) to achieve high-throughput ptychography by optimizing the parameters of the illumination beam. One technique we developed is increasing the illumination flux by using a double-multilayer monochromator (DMM) optics with about 0.8% bandwidth. Compared with our double-crystal monochromator (DCM) optics with 0.01% bandwidth,this DMM optics provides around 20 times more flux. A multi-wavelength reconstruction method has been implemented to deal with the resulting degraded temporal coherence from such an illumination to ensure high-quality reconstruction. In the other work, we adopt a novel use of flat-top focusing optics to generate a flat-top beam with the diameter of about 1.5 mu m on the focal plane. The better uniformity of the probe and the large beam size allow one to significantly increase the step size in ptychography scans and thereby the imaging efficiency.

Motivated by the advanced photon source upgrade, a new hard X-ray microscope called "Velociprobe" has been recently designed and built for fast ptychographic imaging with high spatial resolution. We are addressing the challenges of high-resolution and fast scanning with novel hardware designs, advanced motion controls, and new data acquisition strategies, including the use of high-bandwidth interferometric measurements. The use of granite, air-bearing-supported stages provides the necessary long travel ranges for coarse motion to accommodate real samples and variable energy operation while remaining highly stable during fine scanning. Scanning the low-mass zone plate enables high-speed and high-precision motion of the probe over the sample. With an advanced control algorithm implemented in a closed-loop feedback system, the setup achieves a position resolution (3σ) of 2 nm. The instrument performance is evaluated by 2D fly-scan ptychography with our developed data acquisition strategies. A spatial resolution of 8.8 nm has been demonstrated on a Au test sample with a detector continuous frame rate of 200 Hz. Using a higher flux X-ray source provided by double-multilayer monochromator, we achieve 10 nm resolution for an integrated circuit sample in an ultrafast scan with a detector's full continuous frame rate of 3000 Hz (0.33 ms per exposure), resulting in an outstanding imaging rate of 9 × 104 resolution elements per second.

Among different techniques based on x-ray nanoimaging, ptychography has become a popular tool to study specimens at nanometer-scale resolution without the need of using high-resolution optics that requires very stringent manufacturing processes. This high-resolution imaging method is compatible with other imaging modalities acquired in scanning microscopy. At the Advance Photon Source (APS), we have developed two fluorescence microscopes for simultaneous ptychography and fluorescence imaging which together provide a powerful technique to study samples in biology, environmental science, and materials science. Combined with different tilted sample projections, such correlative methods can yield high-resolution 3D structural and chemical images. More recent work has been focused on the development of a fast ptychography instrument called the Velociprobe which is built to take advantage of the over 100 times higher coherent flux provided by the coming APS upgrade source. The Velociprobe uses high-bandwidth accurate interferometry and advanced motion controls with fast continuous scanning schemes which are optimized for large-scale samples and 3D high-resolution imaging. This instrument has been demonstrated to obtain sub-10 nm resolution with different high-photon-efficient scanning schemes using fast data acquisition rate up to 3 kHz (currently limited by detector's full continuous frame rate). A ptychographic imaging rate of 100 _m2/second with a sub-20 nm spatial resolution was shown in this paper.

Journal Article High-speed and Large Field-of-view Imaging via X-ray Fly-scan Ptychography Get access Yi Jiang, Yi Jiang Advanced Photon Source, Argonne National Laboratory, Lemont, USA Corresponding author: yjiang@anl.gov Search for other works by this author on: Oxford Academic Google Scholar Junjing Deng, Junjing Deng Advanced Photon Source, Argonne National Laboratory, Lemont, USA Search for other works by this author on: Oxford Academic Google Scholar Jeffrey A Klug, Jeffrey A Klug Advanced Photon Source, Argonne National Laboratory, Lemont, USA Search for other works by this author on: Oxford Academic Google Scholar Yudong Yao, Yudong Yao Advanced Photon Source, Argonne National Laboratory, Lemont, USA Search for other works by this author on: Oxford Academic Google Scholar Curt Preissner, Curt Preissner Advanced Photon Source, Argonne National Laboratory, Lemont, USA Search for other works by this author on: Oxford Academic Google Scholar Christian Roehrig, Christian Roehrig Advanced Photon Source, Argonne National Laboratory, Lemont, USA Search for other works by this author on: Oxford Academic Google Scholar Zhonghou Cai, Zhonghou Cai Advanced Photon Source, Argonne National Laboratory, Lemont, USA Search for other works by this author on: Oxford Academic Google Scholar Barry Lai, Barry Lai Advanced Photon Source, Argonne National Laboratory, Lemont, USA Search for other works by this author on: Oxford Academic Google Scholar Stefan Vogt Stefan Vogt Advanced Photon Source, Argonne National Laboratory, Lemont, USA Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 25, Issue S2, 1 August 2019, Pages 46–47, https://doi.org/10.1017/S1431927619000965 Published: 01 August 2019

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Focused probe based beamlines at synchrotron sources perform a variety of microscopy techniques, recording different signals under a wide array of conditions on a wide array of samples. Generally, increasing flux in a smaller beam spot size will increase the output of the beamline. High quality focusing optics are key to and improvements to the optics have a direct benefit to the performance of the beamline. This need for high performance optics will become greater as new generation of synchrotron sources are turned on based on multi-bend achromat rings such as the Advanced Photon Source Upgrade (APS-U).

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Fresnel-zone-plate-based optics is extensively applied for x-ray instruments. At the Advanced Photon Source (APS) at Argonne National Laboratory (ANL), many synchrotron radiation beamlines are using Fresnel zone plates for hard x-ray focusing. However, the efficiency of Fresnel zone plates (FZPs) as focusing optics for x-rays depends on the height of the structures. In the hard x-ray regime, very high aspect ratios are required for maximum efficiency with focusing spot in few tens of nanometers, which is required for future hard xray nanoprobe beamlines planned as part of the APS Upgrade project [1,2]. To overcome the limitations of today’s fabrication techniques for high-efficiency hard xray FZPs, a new approach of stacking FZPs at larger distances (in an intermediate-field) was published by Vila-Comamala et al. in 2012 [3]. According to this new approach, stacking zone plates with large separation distance is possible by adjusting the diameter of the downstream FZP so that its focal length is equal to the focal length of the upstream FZP minus the distance between both FZPs. Thus, the focal spots of both FZPs overlay when the separation of both FZPs is matching the difference in focal lengths. However, besides designing and fabricating of high quality FZPs for intermediate-field stacking, there are many mechanical design challenges to transfer the theory to a practical instrument. First of all, a precision alignment apparatus for multiple FZPs handling and aligning must be designed to meet the following challenging design requirements: • Each of the stacking FZPs need to be manipulated in three dimensions with nanometer-scale resolution and several millimeters travel range. • The relative three-dimensional stabilities between all of the stacking FZPs (especially in the x-ray beam transverse plane) are required to be kept within few nanometers for more than eight hours, the duration of the hard x-ray focusing for nanoprobe operation. • Compatible with the operation of multiple optics configuration for the APS future x-ray nanoprobe design. To meet the demanding mechanical requirement for the precision alignment apparatus system for the hard x-ray focusing in twenty-nanometer scale, several prototypes have been designed and tested at the APS. Figure 1. A 3-D model of a prototype of Z2-33 alignment apparatus for two FZPs stacking. Figure 1 shows a 3-D model of a prototype of alignment apparatus Z2-33 for two FZPs stacking [4]. It enabled the first experiment of stacking FZPs with adjusted diameter in the intermediate field, and the results prove the simulations by Vila-Comamala et al. [3]. It includes a pair of commercial Piezo-motordriven linear stages (SmarAct SLC-1720S), which are mounted on the zone plate alignment base to provide 2-D alignment for the upstream zone plate in X-Y plane. The downstream zone plate holder is driven by a SmarAct SLC1720S linear stage in Z-direction to adjust the gap distance between the upstream and downstream zone plates. All of the three piezo linear positioners are mounted on a zone plate alignment base frame, which is a part of the carriage of a 2D-tilting stage. Driven by a picomotor actuator, the V-axis tilting stage rotates around a vertical pin, which is fixed on the base of the 2D-tilting stage and sliding fitted with the base of the H-axis stage. The H-axis stage tilts around a pair of flexural pivot as shown in figure 1. Figure 2 shows a 3-D model of a prototype of alignment apparatus for three FZPs stacking [4,5]. Its non-symmetric design is also compatible with mirror-based nanofocusing optics, such as Kirkpatrick-Baez (K-B) mirrors [6] for hard x-ray nanoprobe in switchable multioptics operation modes. As shown in figure 2, the Z2-34 alignment apparatus has a nonsymmetric invar base structure (1) and six commercial Piezo-motor-driven linear stages (SmarAct SLC-1720S). Three zone plates (24) are mounted on CVD-diamond holders (5-7). The CVD-diamond holder (5) for upstream zone plate (2) is driven by a stage (8) to adjust its position in Z direction with nanometer scale and stability. The second downstream zone plate (3) is driven by a pair of stages (9,10) to adjust its position in X and Y directions. The third downstream zone plate (4) is driven by a set of stages (11-13) to adjust its position in X, Y, and Z directions. Since the thermal expansion coefficient of CVD diamond is similar to the thermal expansion coefficient of invar, it can basically ensure thermal stability of the apparatus. To further compensate the thermal deformation from the stages (8), (9,10), and (1113), the materials of the linkage components (14-16) between the stages and CVD-diamond holders are carefully chosen. If it is necessary, two or three materials may be combined to compensate the stages thermal deformation precisely. Figure 3 shows a photograph of the Z2-34 alignment apparatus for three FZPs stacking. Figure 2. A 3-D model of a prototype of Z2-34 alignment apparatus for three FZPs stacking with non-symmetric invar base structure and CVDdiamond ZLP holders. The precision mechanical design of the apparatus prototypes for two and three FZPs alignment in intermediate-field, as well as the test results of their hard x-ray focusing performances are presented in this paper. Design of the apparatus for six and more FZPs will also be presented in the paper. Figure 3. A photograph of the Z2-34 alignment apparatus for three FZPs stacking test at the APS 2ID-E hard x-ray experiment station.