Copyright: Dr. Marc Wenskat
Funded Projects 2018
Influence of Nitration of SRF grade Niobium on Kapitza Resistance and Thermal Conductivity
Dr. Marc Wenskat (UHH)
Project Partners: Guilherme Dalla Lana Semione, Christopher Bate
Superconducting radio-frequency (SRF) cavities are the workhorse for modern accelerators, whether for the European Spallation Source, the European XFEL or LCLSII and the cavity production for the European XFEL set standards. But in recent years, new treatments have emerged. In particular the LCLSII cavity production is based on a treatment which mechanisms remain mysterious. These so called “nitrogen doped” cavities have a lower surface resistance RS by a factor 2-3 in the operational range for a continuous wave machine, which drastically reduces operational costs, but the maximum accelerating field was also reduced by about 30%. Another improvement is the “nitrogen infusion” process, which reduces Rs but maintains the accelerating field. This process is difficult to control and not all relevant process parameters are yet identified. None of the new treatments are understood in terms of surface processes or relation to cavity performance. We want to investigate our new hypotheses to explain the reduced accelerating field for nitrogen-doped cavities. In parallel we will test a theory for the origin of the reduced Rs. If the hypothesis is found to be correct, the limitation of doped cavities can be overcome. But even more important, a new insight in the relation of surface properties and cavity performance would be achieved.
Probing unknown iron uptake mechanisms in the human malaria parasite Plasmodium falciparum using a structural systems biology approach
Copyright: Prof. Dr. Tim-Wolf Gilberger
Prof. Dr. Tim - Wolf Gilberger (UHH/CSSB)
Project Partners: Dr. Strauß (EMBL), Dr. Christian Löw (EMBL)
Iron is a key element for life on Earth due to its broad function as biocatalyst and flexible redox chemistry. However, its low bioavailability limits life in many environments and cells need to acquire iron against a concentration gradient using efficient iron uptake systems.
The human malaria parasite Plasmodium falciparum – responsible for 400,000 deaths per year – depends on iron from the blood to proliferate. Nutritional immunity reactions that limit the availability of iron and other trace metal nutrients to parasites are a major part of the human defense against infections. Hence, iron levels are tightly controlled and low concentrations of free iron control the proliferation of P. falciparum. Indeed, adding iron binding agents has cytocidal effects on the parasite.
Surprisingly, despite its great potential as antimalarial drug target, the molecular mechanisms of iron acquisition in P. falciparum from its host are insufficiently studied and our understanding remains elusive. This is exacerbated by the fact that up to 50% of the genes encoded in the genome of P. falciparum remain unknown due to its unique evolutionary history from a free-living photosynthetic organism to an obligate parasite.
We will address this knowledge gap using an integrative approach by combining continuous cell culturing of Plasmodium falciparum with transcriptome and proteome profiling to identify iron-responsive gene and protein networks and characterize unknown proteins using biochemistry and X-ray crystallography.
Pulse-post compression in gas-filled multi-pass cells
Copyright: Dr. Christoph Heyl
Dr. Christoph Heyl (FS-LA)
Prof. Markus Drescher (Group leader); (UHH),
Dr. Tino Lang (Team leader within FS-LA); (DESY; FS-LA)
Dr. Cord Arnold (University Lecturer), Lund University, Sweden
Ultrashort laser pulses, nowadays employed for a variety of applications ranging from material processing to gravitational wave detection, can undergo nonlinear interactions if sufficiently high intensities are reached.
Such nonlinear interactions do not only form the basis of modern laser technology, but have also led to the emergence of completely new research fields such as attosecond science. They found applications within modern surgery and might enable lightning control. Via nonlinear light matter interactions, light can control light. Laser light at the nominal wavelength can be transformed into a beautiful white light supercontinuum, covering the entire visible spectral regime and extending far beyond its frontiers.
The precise control of nonlinear light-matter interaction is possible for example in guiding structures such as optical fibers, which guide laser light over long distances. As a striking alternative, researchers have only very recently designed an optical resonator-like system, which provides completely new degrees of freedom for controlling nonlinear light matter interactions by replacing the guiding optical fiber with a simple mirror arrangement. The idea is simple but remarkably effective: instead of letting a light pulse pass a nonlinear medium once, we can now bundle the laser beams and send them again and again through the same medium while altering their properties in-between. This way, we foresee that new regimes for laser intensity, wavelength and pulse-duration can be reached. The scientific objective of this project is the investigation of novel methods to control nonlinear light-matter interaction in multi-pass cell arrangements. Using gases as nonlinear media, we explore the power-scalability of this scheme and its potential to reach new spectral regimes.
Variable-temperature surface high-energy x-ray diffraction for in situ and operando studies of amorphous, polycrystalline, and epitaxial thin films
Dr. Ann - Christin Dippel (PETRA III/ DESY)
Prof. Dorota Koziej (Institut für Nanostruktur- und Festkörperphysik); (UHH),
Marin Roelsgaard (PETRA III); (DESY & Aarhus University)
Anita Ehnes (PETRA III); (DESY)
Florian Bertram (PETRA III); (DESY)
The fundamental relationship between atomic structure and macroscopic properties represents one of the elementary foundations of materials science. In the case of thin films, the confinement of one dimension to the nanometer range adds to the complexity of the structure-property relationship. Surface x-ray diffraction and scattering techniques in grazing incidence geometry enable the extraction of structural information on the atomic scale. Following the structure evolution and structural changes in situ or operando during thin film fabrication and operation is the most direct way to link the atomic arrangement and the macroscopic properties of functional layers and devices.
In thin film technology, thermal treatment is applied as an essential step of synthesis and functionalization in most physical and chemical deposition processes such as atomic layer deposition, sputtering, spin-on or dip coating. Moreover, in numerous applications, thin film components are operated at non-ambient, varying temperatures, e.g. gas sensors, catalysts, and thermoelectric modules.
This project aims at developing a sample environment for in situ and operando characterization of thin film processes by surface high-energy x-ray diffraction under non-isothermal conditions. High photon energies are required owing to their benefits when working in bulky sample chambers with limited size of the exit window for the scattered intensity. At the same time, they allow for the study of disordered and amorphous materials by pair distribution function analysis. In order to keep the sample surface stable within the x-ray beam vertically focused to 2 μm and at the critical angle in the order of 0.01° during temperature variation, we will design a minimal thermal expansion sample holder with an active feedback system based on laser interferometry. We will test the efficiency of this stabilization method for different temperature ranges and ramp rates relevant e.g. for molecular beam epitaxy of magnetic films, crystallization of spin-coated electronic layers, as well as photo-electrochemical reactions and operation of thermoelectric films.
Biomolecular dynamics at sub-nanometer resolution
Prof. Dr. Nicole Fischer (Institute for Medical Microbiology, Virology and Hygiene; University Medical Center Hamburg - Eppendorf)
Dr. Eike C. Schulz (MPSD, CUI)
Dr. Günther Kassier (MPSD, CUI)
Prof. Dr. Henning Tidow (UHH)
In Liquid-phase or in-situ transmission electron microscopy (in-situ EM) specimens are not dried or frozen but are encapsulated in nanofluidic cells and remain in solution. Therefore in-situ EM has the potential to understand biomolecular structure and dynamics at physiological conditions. However, currently the technology is limited to lower resolutions (nm’s) mainly due to the inherent background scattering of the nano-fluidic cells and the thickness of solvent layer in the electron beam path. Therefore, it is the aim of this project to overcome both of these limitations. To realize these goals, we will utilize latest developments in nano-fabrication technology to produce the next generation of nano-fluidic cells. These next-generation cells will improve image quality, enabling higher resolution images at lower electron dose. With these improved nanofluidic cells in-situ EM has the potential to provide image quality on par with cryo-EM. This will enable us to record movies of single molecule dynamics under true physiological conditions at (sub)-nanometer resolution. To demonstrate the capabilities of the next-generation nano-fluidic cells we will use successively smaller model systems: including bacteria, viruses and integral membrane proteins. In particular, we are aiming to elucidate biomolecular dynamics of infectious pathogens by analysing the process of virus assembly by using clinically relevant polyomaviruses and initial steps of bacterial infection as an example using the type III secretion system of bacteria.