Showing papers by "Joachim Schulz published in 2019"

The Single Particles, Clusters and Biomolecules and Serial Femtosecond Crystallography instrument of the European XFEL: initial installation

Abstract: The European X-ray Free-Electron Laser (FEL) became the first operational high-repetition-rate hard X-ray FEL with first lasing in May 2017. Biological structure determination has already benefitted from the unique properties and capabilities of X-ray FELs, predominantly through the development and application of serial crystallography. The possibility of now performing such experiments at data rates more than an order of magnitude greater than previous X-ray FELs enables not only a higher rate of discovery but also new classes of experiments previously not feasible at lower data rates. One example is time-resolved experiments requiring a higher number of time steps for interpretation, or structure determination from samples with low hit rates in conventional X-ray FEL serial crystallography. Following first lasing at the European XFEL, initial commissioning and operation occurred at two scientific instruments, one of which is the Single Particles, Clusters and Biomolecules and Serial Femtosecond Crystallography (SPB/SFX) instrument. This instrument provides a photon energy range, focal spot sizes and diagnostic tools necessary for structure determination of biological specimens. The instrumentation explicitly addresses serial crystallography and the developing single particle imaging method as well as other forward-scattering and diffraction techniques. This paper describes the major science cases of SPB/SFX and its initial instrumentation – in particular its optical systems, available sample delivery methods, 2D detectors, supporting optical laser systems and key diagnostic components. The present capabilities of the instrument will be reviewed and a brief outlook of its future capabilities is also described.

Megahertz x-ray microscopy at x-ray free-electron laser and synchrotron sources

Abstract: Modern emerging technologies, such as additive manufacturing, bioprinting, and new material production, require novel metrology tools to probe fundamental high-speed dynamics happening in such systems. Here we demonstrate the application of the megahertz (MHz) European X-ray Free-Electron Laser (EuXFEL) to image the fast stochastic processes induced by a laser on water-filled capillaries with micrometer-scale spatial resolution. The EuXFEL provides superior contrast and spatial resolution compared to equivalent state-of-the-art synchrotron experiments. This work opens up new possibilities for the characterization of MHz stochastic processes on the nanosecond to microsecond time scales with object velocities up to a few kilometers per second using XFEL sources.

A versatile liquid-jet setup for the European XFEL

Abstract: The SPB/SFX instrument of the European XFEL provides unique possibilities for high-throughput serial femtosecond crystallography. This publication presents the liquid-jet sample delivery setup of this instrument. The setup is compatible with state-of-the-art gas dynamic virtual nozzle systems as well as high-viscosity extruders and provides space and flexibility for other liquid injection devices and future upgrades. The liquid jets are confined in a differentially pumped catcher assembly and can be replaced within a couple of minutes through a load-lock. A two-microscope imaging system allows visual control of the jets from two perspectives.

Optimization of laser writer-based UV lithography with high magnification optics to pattern X-ray lithography mask templates

Abstract: Deep X-ray lithography is a preferred fabrication approach for those micro devices that depend on smooth and vertical sidewalls of comparatively deep structures rather than extreme lateral resolution. The structure quality obtained depends on, and is limited by, the quality of the X-ray mask applied. A critical component of the mask is its absorber patterns. They get fabricated by electroplating into voids of a polymer template. These templates must usually be at least 3 μm deep and exhibit smooth and vertical sidewalls with a lateral resolution of micrometers and possibly below. Primary patterning of the templates is very demanding. Best results are obtained when dedicated electron beam writers with acceleration voltages of 100 kV and above are applied. This, however, limits access to patterning infrastructure and substantially drives delivery timeline and cost, making mask absorber template patterning a bottleneck of the entire process sequence. We propose, evaluate and optimize an alternative absorber patterning approach based on direct laser writing. An ultraviolet laser with 355 nm wavelength and 250 mW beam power by Heidelberg Instruments is applied to expose 2.9 μm thick, chemically amplified, high contrast, negative tone resist mrx-5. Exposure parameters analyzed include the dose and focal settings. Experiments are carried out on bare silicon wafers as well as on chrome-gold and on titanium oxide plating bases. For all cases, results with and without an additional antireflective coating of 200 nm AZ BAR-Li are studied. Aspects of the resist template structure quality analyzed include the sidewall verticality and its smoothness and defects, resist adhesion to the substrate, minimum feature size and structure accuracy, as well as irregularities due to stitching of partial layouts. In an optimized process, a dose of 14 mW on oxidized titanium and BAR-Li was used. We were able to demonstrate 1.5 μm minimum feature size of isolated structures and structural details of about 1 μm. The sidewalls are vertical and exhibit a roughness of dozens of nanometers. When an antireflective coating is used, chamfers are observed at the resist bottom. The structure accuracy occasionally deviates from the original layout by 200–300 nm, particularly at stitching singularities or towards the end of resist walls. The described absorber template patterning process delivers a resolution that much extends beyond previous UV patterning approaches. The structure accuracy, however, is inferior to electron beam written samples. Given the cost and timeline benefit, results of the study will allow users to identify which primary patterning approach is best suited for their micro devices.

Native mass spectrometry provides sufficient ion flux for XFEL single-particle imaging.

Abstract: The SPB/SFX instrument at the European XFEL provides unique conditions for single-particle imaging (SPI) experiments due to its high brilliance, nano-focus and unique pulse structure. Promising initial results provided by the international LCLS (Linac Coherent Light Source) SPI initiative highlight the potential of SPI. Current available injection methods generally have high sample consumption and do not provide any options for pulsing, selection or orientation of particles, which poses a problem for data evaluation. Aerosol-injector-based sample delivery is the current method of choice for SPI experiments, although, to a lesser extent, electrospray and electrospinning are used. Single particles scatter only a limited number of photons providing a single orientation for data evaluation, hence large datasets are required from particles in multiple orientations in order to reconstruct a structure. Here, a feasibility study demonstrates that nano-electrospray ionization, usually employed in biomolecular mass spectrometry, provides enough ion flux for SPI experiments. A novel instrument setup at the SPB/SFX instrument is proposed, which has the benefit of extremely low background while delivering mass over charge and conformation-selected ions for SPI.

Creating round focused micro-jets from rectangular nozzles

Abstract: A focused jet is an axisymmetric jet of liquid surrounded by an outer coaxial gas jet. The gas jet is typically used to compress the liquid jet in the radial direction thereby focusing it. At microscales, it is difficult to manufacture micro-scale delivery nozzles (needles) and to consistently align and axially position the liquid and the gas needles. However, it is very easy, using standard etching technologies to make precise and repeatable rectangular nozzle designs. This work will therefore explore the geometric and fluid dynamics constraints that allow one to design rectangular nozzles that produce round coaxial micro-jets of liquid and gas. Because of the small scales, the fluid dynamics of the focusing jet is unusual, and this work demonstrates that the liquid jet is best focused by shear stretching and not via gas compression. This paper shows that sheet jetting occurs when the Reynolds number of the gas is too high. Dripping occurs when the Weber number of the liquid is too low. The desired round jet occurs by balancing Weber number of the liquid jet and Reynolds number of the gas such that surface tension at the interface holds the water jet round while the acceleration of the water jet due to shear at the interface from fast-moving air causes the liquid jet cross-sectional area to decrease. The goal of this initial paper is to demonstrate that a parameter region exists where this flow behavior is possible.