Copyright: Dr. Marcus Seidel
Funded Projects 2020
Mid-infrared Frequency Comb Spectroscopy of Hybrid Light-Matter States
Dr. Marcus Seidel (DESY)
Project Partners: Dr. Holger Lange (Institut für Physikalische Chemie, UHH), Dr. Ingmar Hartl (DESY FS-LA Laser Science and Technology), Dr. Peter G. Schunemann (BAE Systems, USA), Dr. Valentin J. Wittwer (Laboratoire Temps-Fréquence, Institut de Physique, Université de Neuchâtel, Schweiz)
The strong coupling of optical cavity or plasmonic modes to dipole transitions results in the formation of hybrid light-matter states, so-called polaritons. The light hybridization of molecular vibrations has recently led to significant modifications of chemical reactivity and superconducting phase transitions. It has been shown that the coupling strength between light and matter is decisive for exploiting the novel phenomena. As known from quantum optics, the coherence degree of the polaritons, quantified in cooperativity, is expected to present another control knob for tuning material properties. Here, we propose to demonstrate vibrational strong coupling systems with unprecedentedly high cooperativity by firstly, employing Fabry-Pérot cavities with quality factors 100 times higher than state-of-the-art, and secondly, by using plasmonic nanoparticle crystals which have recently led to record-high coupling strengths in the visible region. To characterize the high-cooperativity systems, we propose to apply frequency comb spectroscopy for the first time to strongly coupled matter. Enabled by the superior spatial and temporal coherence of the comb in comparison to commonly used thermal mid-infrared sources, we will overcome the current experimental limitations which have hampered so-far the investigation of high-quality cavities and micrometer-scale effects. The proposed experiments will lay the ground work for boosting vibrational strong coupling chemistry and material science.
X-ray fluorescence imaging of labelled T-cells with a laser-driven X-ray source
Dr. Theresa Staufer (UHH)
Project Partners: Prof. Dr. Florian Grüner (UHH); Dr. Wim Leemans (DESY); Dr. Jens Osterhoff (DESY); Prof. Dr. Samuel Huber (UKE), Prof. Dr. Wolfgang Parak (UHH)
Laser-wakefield acceleration in combination with Thomson scattering offers the possibility to produce highly brilliant X-rays in a compact setup. Several research groups at the University of Hamburg and DESY have improved and stabilised this laser-driven acceleration scheme, making it an attractive alternative to conventional accelerators which typically have a footprint on the order of hundreds of meters.
X-Ray Fluorescence Imaging (XFI) is a medical imaging modality based on the use of scanning pencil X-ray beams for the in vivo localisation of functionalised nanoparticles. It offers very high sensitivity, spatial resolution and long-duration serial measurements which are highly beneficial in early-tumour diagnostics and pharmacokinetic tracking studies. XFI is regarded as a potential novel pre-clinical and clinical imaging tool that could offer new data that are not accessible as of yet. One example is in vivo cell tracking for studying the dynamics of the population of immune cells that are relevant in finding new therapies for so-called immune-mediated inflammatory diseases, such as Crohn's Disease.
However, the brilliant and narrow bandwidth radiation needed for XFI is nowadays provided only by synchrotrons, but as those machines have large circumferences, they are not suited for applications in a clinical environment. Consequently, for producing radiation properties that can also be used for such applications, it is necessary to further increase the stability of laser-driven sources.
The goal of the proposed project is to demonstrate a proof-of-principle experiment where immune cells labelled with nanoparticles will be localised in a mouse phantom with X-rays produced in a laser-wakefield accelerator setup. The results from this compact laser-driven X-ray source will be compared with our findings from using a large-scale synchrotron and in turn used to optimize the Thomson source for medical X-ray fluorescence imaging purposes.
Electro-optical imaging of the electric field in semiconductor detectors
Dr. Annika Vauth (UHH)
Project Partners: David Pennicard (DESY FS-DS), Erika Garutti (UNI-HH IExp.), Heinz Graafsma (DESY FS-DS), Robert Klanner (UNI-HH IExp.), Jörn Schwandt (UNI-HH IExp)
Solid-state silicon detectors are used in X-ray science as well as in particle and astro-particle physics. In addition, they are employed in many industrial and scientific applications, including medical instruments.
The knowledge of the electric fields in solid state detectors is essential for their understanding and optimization. For radiation damaged silicon sensors, for example sensors used at the Large Hadron Collider at CERN, and for X-ray detectors made of high-Z semiconductors used at X-ray sources, the electric fields are only poorly understood.
The project aims to use the so-called Franz-Keldysh effect for directly determining these fields. For light with photon energies close to the band gap of the semiconductor, this effect leads to a dependence of light absorption on the electric field. We will perform measurements on non-irradiated and later also on irradiated sensors. In our setup, we place our sample under test in the same beam of parallel light as a reference sample. The transmitted light is measured using a 2D InGaAs pixel sensor. By measuring at different wavelengths in the vicinity of the band gap, the electric field (averaged over the light path) will be determined.
The objective of this project is to establish a method to determine the electric field in radiation-damaged silicon detectors as a function of irradiation fluence and particle type, temperature and bias voltage.
Understanding the Molecular interface between PrPC and Abeta amyloid: possible applications in drug design
Dr. Mohsin Shafiq (UKE)
Project Partners: Dr. Carolin Seuring (CSSB), Prof. Dr. Markus Glatzel (Institute for Neuropathology, UKE), Prof. David A. Harris (Department of Biochemistry, Boston University School of Medicine, USA)
The cellular prion protein (PrPC) has been shown to impart a dual role to the progression of the Alzheimer’s disease (AD); extracellularly shed and cleaved forms of PrPC along with exosomally expressed PrPC are suggested to sequester Aβ oligomers (Aβo) and accelerate the Aβ fibril formation; thereby playing a neuroprotective role. In contrast, PrPC molecules expressed on the neuronal surface serves as receptors for Aβo and initiate neurotoxic signaling. In collaboration with Svergun’s group (EMBL Hamburg), using Small angle X-ray scattering, we have found that the presence of PrPC expressing (WT) exosomes facilitates the Aβ fibrillation process compared to PrPC deficient (KO) Exosomes. We hypothesize that modulation of Aβo/cell surface PrPC and Aβo/exosomal PrPC interaction can lead to the development of novel therapeutic approaches. Here we plan to
• Obtain structural insights into the Aβ/PrP complex and Aβ/exosome complexes using negative-stain electron microscopy and FIB/SEM technology, respectively
• Screen of possible drug targets interfering with the Aβ/PrP formation and formation of Aβ/exosome complexes at structural levels
The biophysical characterization and the EM work planned will help us in retrieving crucial mechanistic insights of key players of the aggregation cascade and possible differential drug targets. The data obtained will also provide us the basis for designing future studies based on cryoelectron tomography to gain the high-resolution structure information of Aβ/PrPC complexes, hence improving our understanding towards the receptor functions of PrPC.
Machine Learning with FPGAs for real-time characterization of fast scintillation signals
Dr. Torben Ferber (DESY)
Project partners: Dr. Belina von Krosigk (UHH), Dr. Savino Longo (DESY)
Calorimeters in high energy physics are widely used to measure the energy position and timing of particles.
The Belle II experiment recently introduced a new feature to their CsI(Tl) crystal calorimeter: Offline pulse shape discrimination which is a new technique to identify strongly interacting particles.
Made possible by the recent advances in machine learning (ML) and the availability of powerful FPGAs we want to push this technique one step further and apply pulse shape discrimination not just offline but in real-time.
In this cross-disciplinary project we will bring together Belle II and the SuperCDMS experiment to solve common challenges towards implementing ML algorithms for waveform characterisation on FPGAs.
Performance will be benchmarked using digitised CsI(Tl) scintillator signals from neutron backgrounds in XFEL and cosmic rays.
In the second phase of this project we want to extend real-time pulse shape discrimination to the scintillation timing frontier using the much faster pure CsI crystals.
The project shall seed fast ML on specialized hardware, pulse shape discrimination in a possible Belle II upgrade with pure CsI crystals, and ultimately 6D (position, energy, time, and pulse shape) reconstruction of calorimeters.