Segmented flow generator for serial crystallography at the European X-ray free electron laser

Serial femtosecond crystallography (SFX) with X-ray free electron lasers (XFELs) allows structure determination of membrane proteins and time-resolved crystallography. Common liquid sample delivery continuously jets the protein crystal suspension into the path of the XFEL, wasting a vast amount of sample due to the pulsed nature of all current XFEL sources. The European XFEL (EuXFEL) delivers femtosecond (fs) X-ray pulses in trains spaced 100 ms apart whereas pulses within trains are currently separated by 889 ns. Therefore, continuous sample delivery via fast jets wastes >99% of sample. Here, we introduce a microfluidic device delivering crystal laden droplets segmented with an immiscible oil reducing sample waste and demonstrate droplet injection at the EuXFEL compatible with high pressure liquid delivery of an SFX experiment. While achieving ~60% reduction in sample waste, we determine the structure of the enzyme 3-deoxy-D-manno-octulosonate-8-phosphate synthase from microcrystals delivered in droplets revealing distinct structural features not previously reported

Development of a method to measure the polarization of laser-accelerated protons

In the framework of this thesis first measurements and simulation studies on polarization observables of laser-accelerated charged particle beams were performed. These investigations were carried out with thin foil targets, that were illuminated by 100 TW laser pulses at the ARCturus laser facility at Heinrich Heine University in Düsseldorf, which serve as a source for few MeV proton beams. With Particle-in-Cell simulations the influence of the huge magnetic field gradients, that are inherently present in laser-induced plasmas, on particle trajectories has been modeled. It was found, that the deflection of the protons by a Stern-Gerlach like interaction with the magnetic field gradients is negligibly small and that no spatial separation of the protons according to their spin states is to be expected. Measurements of proton energy spectra have been carried out with a spectrometer dipole that was specifically designed for this purpose. The experimental method for the measurement of the spin-polarization of the proton beam was developed and optimized with the help of Monte-Carlo simulations. It is based on the spin dependency of hadronic proton scattering off nuclei in a scattering target. The feasibility of the method was demonstrated in a null-experiment with the supposedly unpolarized proton beams

Polarization measurement of laser-accelerated protons

We report on the successful use of a laser-driven few-MeV proton source to measure the differential cross section of a hadronic scattering reaction as well as on the measurement and simulation study of polarization observables of the laser-accelerated charged particle beams. These investigations were carried out with thin foil targets, illuminated by 100 TW laser pulses at the Arcturus laser facility; the polarization measurement is based on the spin dependence of hadronic proton scattering off nuclei in a Silicon target. We find proton beam polarizations consistent with zero magnitude which indicates that for these particular laser-target parameters the particle spins are not aligned by the strong magnetic fields inside the laser-generated plasma

Integrated Detector Control and Calibration Processing at the European XFEL

The European X-ray Free Electron Laser is a high-intensity X-ray light source currently being constructed in the area of Hamburg, that will provide spatially coherent X-rays in the energy range between $0.25\,\mathrm{keV}$ and $25\,\mathrm{keV}$. The machine will deliver $10\,\mathrm{trains/s}$, consisting of up to $2700\,\mathrm{pulses}$, with a $4.5\,\mathrm{MHz}$ repetition rate. The LPD, DSSC and AGIPD detectors are being developed to provide high dynamic-range Mpixel imaging capabilities at the mentioned repetition rates. A consequence of these detector characteristics is that they generate raw data volumes of up to $15\,\mathrm{Gbyte/s}$. In addition the detectors on-sensor memory-cell and multi-/non-linear gain architectures pose unique challenges in data correction and calibration, requiring online access to operating conditions and control settings. We present how these challenges are addressed within XFELs control and analysis framework Karabo, which integrates access to hardware conditions, acquisition settings (also using macros) and distributed computing. Implementation of control and calibration software is mainly in Python, using self-optimizing (py) CUDA code, numpy and iPython parallels to achieve near-real time performance for calibration application

Detectors and Calibration Concept for the European XFEL

The European X-ray Free Electron Laser (XFEL.EU) is an international research facility presently under construction in the area of Hamburg, Germany, which will start its operation at the end of 2016. The superconducting linear accelerator of the facility will deliver electron bunches with an energy of up to 17.5 GeV, arranged in trains of typically 2700 bunches at a repetition rate of 4.5 MHz. Each train will be followed by a gap of 99.4 ms. Spatially coherent X-rays are generated from the electron bunches in a series of undulators based on the Self-Amplified Spontaneous Emission (SASE) process, in three photon beamlines extending over a length of up to 200 m. Each beamline serves two experiments with different scientific goals

Calibration and Calibration Data Processing Concepts at the European XFEL

The European X-ray Free Electron Laser (Altarelli, 2006) is a high-intensity X-ray light source currently being constructed in Hamburg, Germany, that will provide spatially coherent X-rays in the energy range between 0.25 keV and 25 keV. The machine will deliver a unique time structure, consisting of up to 2700 pulses, with a 4.5 MHz repetition rate, 10 times per second at very high photon fluxes up to 1017 photons/s (Tschentscher, 2012). The LPD (Hart, 2012; Koch, 2013), DSSC (Porro, 2010, 2012; Lutz, 2010) and AGIPD (Graafsma, 2009) detectors are being developed to provide Mpixel imaging capabilities at the aforementioned repetition rates for a dynamic range spanning from single photon sensitivity to 104 –105 photons per pixel. The detectors are optimized for specific energy ranges. A direct consequence of the aforementioned detectors’ characteristics is that they generate raw data volumes unprecedented in photon science, ranging up to 1Mpixel x 640 memory cells x 10 pulse/s x 16 bit, i.e. 12.8 Gbyte/s. On-detector vetoing may not necessarily lower these rates much - a memory cell freed by a vetoed pulse may be used by data from one of the remaining 2700 pulses a train consists of. The PC-layer may reduce this data amount by additional software triggering, but this is not guaranteed. Figure 1 gives an overview of the different data products at European XFEL, as well as their flows and involved user roles, under the assumption that processing takes place within XFEL’s Karabo framework (Heisen, 2013). In addition to the high data rates, the Mpixel detectors’ on-sensor memory-cell and multi-gain-stage architectures necessary for the high dynamic range, pose unique challenges in detector-specific data corrections and calibration (Weidenspointner, 2012; Sztuk-Dambietz, 2013a). These challenges are addressed by providing a dedicated and thoroughly characterized set of test stands, which utilize continuous sources (Fe-55, X-ray tubes) as well as a pulsed setup: PulXar (Sztuk-Dambietz, 2013b), which is designed to produce X-ray pulses of 50-150 ns duration, within a 0.6 ms burst followed by a 99.4 ms gap. The radiation it produces thus closely matches the XFEL pulse structure. Additionally, simulation tools are being developed to assist in detector characterization (Bohlen and Joy, 2013)

Operational experience with Adaptive Gain Integrating Pixel Detectors at European XFEL

The European X-ray Free Electron Laser (European XFEL) is a cutting-edge user facility that generates per second up to 27,000 ultra-short, spatially coherent X-ray pulses within an energy range of 0.26 to more than 20 keV. Specialized instrumentation, including various 2D X-ray detectors capable of handling the unique time structure of the beam, is required. The one-megapixel AGIPD (AGIPD1M) detectors, developed for the European XFEL by the AGIPD Consortium, are the primary detectors used for user experiments at the SPB/SFX and MID instruments. The first AGIPD1M detector was installed at SPB/SFX when the facility began operation in 2017, and the second one was installed at MID in November 2018. The AGIPD detector systems require a dedicated infrastructure, well-defined safety systems, and high-level control procedures to ensure stable and safe operation. As of now, the AGIPD1M detectors installed at the SPB/SFX and MID experimental end stations are fully integrated into the European XFEL environment, including mechanical integration, vacuum, power, control, data acquisition, and data processing systems. Specific high-level procedures allow facilitated detector control, and dedicated interlock systems based on Programmable Logic Controllers ensure detector safety in case of power, vacuum, or cooling failure. The first 6 years of operation have clearly demonstrated that the AGIPD1M detectors provide high-quality scientific results. The collected data, along with additional dedicated studies, have also enabled the identification and quantification of issues related to detector performance, ensuring stable operation. Characterization and calibration of detectors are among the most critical and challenging aspects of operation due to their complex nature. A methodology has been developed to enable detector characterization and data correction, both in near real-time (online) and offline mode. The calibration process optimizes detector performance and ensures the highest quality of experimental results. Overall, the experience gained from integrating and operating the AGIPD detectors at the European XFEL, along with the developed methodology for detector characterization and calibration, provides valuable insights for the development of next-generation detectors for Free Electron Laser X-ray sources.