Microwavephysics and Atmospheric Physics
Biomedizinische Photonik
Ultrafast Science and Technology
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Last update: 07.05.2018
HS 2016: Seminare über Ultrafast Science and Technology
Thursday 11:15am
Vorträge, die innerhalb der nächsten Tage stattfinden, sind speziell markiert.
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Donnerstag, 15.09.2016

Temporal characterization of X-ray free-electron laser pulses

Zeit: 14:00 Uhr
Hörsaal: B5
Nick Hartmann
Institute of Applied Physics
University of Bern, and
SLAC National Accelerator Laboratory
Menlo Park, CA

Donnerstag, 22.09.2016

X-ray ptychography

Zeit: 11:15 Uhr
Hörsaal: B116
Esther Hsiao-Rho Tsai
Postdoctoral Fellow
Coherent X-Ray Scattering Group
Paul Scherrer Institute PSI

X-ray ptychography is an amplitude and phase sensitive technique based on coherent diffractive imaging. From the nanostructures and network of bone to the porosity of stacked layers in solar cells, ptychography enables the characterization of samples with hierarchical structures in life and material science with nanoscale resolution. The sample is illuminated with a spatially confined beam at overlapping positions, which allows a large imaging field of view as well as the quantitative reconstruction of the spatial distributions of electron density and attenuation of the sample. Laser interferometry is used in the experiment to enhance the scanning precision, pushing the 3D resolution to sub-20nm. The method can also be extended to spectroscopy and magnetic imaging.

Donnerstag, 20.10.2016

Exploring Ultrafast Molecular Dynamics: The Femtosecond X-ray Experiments Instrument

Zeit: 11:15 Uhr
Hörsaal: B116
Dr. Andreas Galler
European XFEL GmbH
22869 Schenefeld, Germany

Understanding the initial steps during ultrafast molecular reactions is a vital goal in structural dynamics research. While pico- and femtosecond x-ray absorption (XAS) as well as x-ray emission (XES) techniques have now matured for geometric structure and oxidation state changes (XAS) [1], and electronic structure changes (XES) [2], we seek to exploit complementary x-ray techniques like x-ray diffuse scattering (XRD) to unravel the complete dynamic sequence(s), which include electronic structure changes (via XES and XAS) next to often concomitant geometric structure changes (via XRD and XAS). These studies represent key experiments that will become readily feasible at the Femtosecond X-ray Experiments (FXE) instrument, permitting simultaneous (or quasi-simultaneous) studies of the same sample with these different tools, down to the shortest time scales available. As state of the art the formation of a high-valent Fe(V) containing complex at biologically compatible conditions, i.e. at room in solution phase is investigated, using the above mentioned x-ray techniques. The European XFEL facility will deliver a remarkably different pulse pattern than any other femtosecond hard X-ray source. It will support 6 Scientific Instruments in the initial configuration with 3 SASE beamlines. The FXE station located at the SASE 1 beamline will make use of the 5-20 keV range for dynamical pump-probe studies offering a highly versatile sample environment setting allowing for gaseous as well as condensed matter experiments. Next to the complete FXE instrument specifications we present benchmark experiments which make use of the FXE built in x-ray techniques at highest time resolution. References: [1] C. Bressler, C. Milne, V. T. Pham, A. El Nahhas, R. M. van der Veen, W. Gawelda, S. Johnson, P. Beaud, D. Grolimund, M. Kaiser, C. N. Borca, G. Ingold, R. Abela, and M. Chergui, Science 323, 489 (2009). [2] W. Zhang, R. Alonso-Mori, U. Bergmann, C. Bressler, M. Chollet, A. Galler, W. Gawelda, R. G. Hadt, R. W. Hartsock, T. Kroll, K. S. Kjær, K. Kubi?ek, H. T. Lemke, H. W. Liang, D. A. Meyer, M. M. Nielsen, C. Purser, J. S. Robinson, E. I. Solomon, Z. Sun, D. Sokaras, T. B. van Driel, G. Vankó, T.-C. Weng, D. Zhu, and K. J. Gaffney, Nature 509, 345 (2014).

Donnerstag, 27.10.2016

Free form surfaces on all optics?

Zeit: 11:15 Uhr
Hörsaal: B116
Dr. Florian Enderli
SwissOptic AG
CH-9435 Heerbrugg

Working at a high precision optics manufacturer opens your eyes for tolerances on mirrors and lenses: There are no perfect optical surfaces. To a certain accuracy, all spherical, planar, or asphaerical surfaces are free form surfaces. They further have allowances for tilt, centricity, scratches, digs, coating defects,… The talk will present Swissoptic as a company, a few examples of its products and my job there including details on salary, holidays and work hours. Further it will give an introduction to precision optics manufacturing and the world of tolerances around it.

Donnerstag, 03.11.2016

The Wonderland of Carbon Dots

Zeit: 11:15 Uhr
Hörsaal: B116
Alice Sciortino
University of Palermo and University of Catania, Italy
Institute of Applied Physics
University of Bern

Carbon nanodots are a new class of optically-active nanomaterials which consist in sub-10 nm nanoparticles composed by carbon, oxygen, nitrogen and hydrogen. Their structure is synthesis-dependent and often consists in a nanocrystalline core having, for instance, a graphite or carbon nitride structure, decorated by a variety of polar functional groups on the surface. The most important hallmark of carbon dots is their photoluminescence, which is intense, tunable and sensitive to the external environment. All of these characteristics, combined with the ease and low cost of the synthesis, high water solubility and non-toxicity, make carbon dots very interesting for applications in different fields, as sensing or optoelectronics. However, many questions remain open at the fundamental physical level, triggering an intense debate in the literature. The presentation is focused on the studies on Carbon Dots recently conducted at University of Palermo, which led to the discovery of a new structure of carbon dots, the understanding of their interactions with different solvents, and the investigation of the interactions between carbon dots and nearby ions in solution and in solid-state. These studies allowed us to better understand the physics behind the carbon dots and, in particular, they suggested an interpretation of the mechanism behind the photoluminescence and allowed to clarify why it is tunable. In the last part of the presentation, the in-depth, undergoing studies, stimulated by the recently born collaboration between University of Palermo and University of Bern, will be presented. They will be focused on the employment of femtosecond transient absorption techniques to resolve the entire photo-cycle of carbon dots and to clarify how different types of interactions between dots and the environment occur.

Donnerstag, 10.11.2016

Electron Beam Diagnostics for FELs and Medical Accelerators

Zeit: 11:15 Uhr
Hörsaal: B116
Dr. Peter Peier
Eidgenössisches Institut für Metrologie METAS
Labor Ionisierende Strahlung

This talk will be divided into two parts. In the first part I will talk about my work at DESY in the MSK group. I will report on the activities of the subgroup which is responsible for designing, installing and commissioning diagnostic elements for longitudinal electron beam properties at European XFEL. I will also point out our efforts to implement (fast) feedback systems to stabilize the electron beam in terms of bunch length and bunch arrival time. In the second part I will give a short introduction to the field of medical accelerators with special emphasis on the Microtron we are using at METAS in the lab for Ionizing Radiation. Furthermore I will outline our plans to install several additional diagnostic elements to fully characterize the electron beam of our accelerator.

Donnerstag, 17.11.2016

Laser Microprocessing with Ultra-Short Laser Pulses: Basics, Limitations and Needs

Zeit: 11:15 Uhr
Hörsaal: B116
Dr. Beat Neuenschwander, Institute for Applied Laser, Photonics and Surface Technologies ALPS of the Bern University of Applied Sciences, Burgdorf

Ultra-short laser pulses represent a versatile tool for laser microprocessing. Possible applications range from laser induced processes up to high energy pulses used e.g. for laser shock peening. The institute for Applied Laser, Photonics and Surface Technologies ALPS of the Bern University of Applied Sciences deals (among others) with high speed surface texturing. Increasing throughput always demands high average power laser systems, optimized and adapted process strategies. But even when working with optimized processes and strategies heat accumulation and/or shielding effects can restrain the power scale up process. We will give an overview about the process/strategy optimization and the todays limitations and needs as well.

Donnerstag, 24.11.2016

Moving from a tabletop experiment to SwissFEL

Zeit: 11:15 Uhr
Hörsaal: B116
Dr. Franziska Frei
Paul Scherrer Institute PSI
Villigen Switzerland

Installation and commissioning of SwissFEL is running at full speed. I would like to give you an overview on this large scale facility from the point of view of a person who was previously used to a tabletop experiment. In particular, I will report about our work on electron beam diagnostics.

Donnerstag, 08.12.2016

Applied Research at ABB

Zeit: 11:15 Uhr
Hörsaal: B116
Dr. Hannes Merbold

I will introduce ABB, its fields of activity, and give a first-hand insight of what it is like to work in the Sensor Technologies group at ABB’s Corporate Research Center. Based on exemplary projects, I will outline our research directions, the technologies we are dealing with, as well as the methods we employ to structure our work. The talk aims at providing background information for current students curious about career options in the industry.

Donnerstag, 15.12.2016

Near-field Raman spectroscopy of Carbyne

Zeit: 11:15 Uhr
Hörsaal: B116
Leidy Marcela Giraldo Castaño
Photonics Lab at ETHZ

Nanoscale structural imaging is a fundamental characterization tool with applications in life sciences, material science, nanoscale fluid dynamics, opto-electronics and semiconductor industries. In addition, research laboratories and academia demand super resolution imaging techniques in order to address fundamental questions mainly in cell biology, neurobiology, microbiology and nanoscale materials. This has motivated and driven the development of high resolution imaging systems leading to a diverse and fast evolution in the last century. Near-field Raman spectroscopy combines the chemical, electronic, vibrational specificity given by Raman scattering. On top, it provides a spatial resolution in the order of few nanometers. This multipurpose technique permits the correlation of topographic and optical information making it attractive to study the characteristics of nanoscale objects. During the talk it will be presented a summary of near-field Raman imaging experiments on carbyne, a truly one-dimensional material formed by a chain of carbon atoms. Carbyne is a promising material for the next generation of nanoelectronic devices and its properties are still under research. Correlation between the length of carbyne chains and its Raman mode is discussed and first steps towards determining the phonon coherence length in carbyne by near-field Raman spectroscopy are presented.

Donnerstag, 22.12.2016

Gamma Spectrometry at SPIEZ LABORATORY

Zeit: 11:15 Uhr
Hörsaal: B116
Dr. Nina Mosimann
SPIEZ LABORATORY, Radioactivity Group
Federal Office for Civil Protection FOCP
3700 Spiez

As the Swiss Federal Institute for nuclear, biological and chemical (NBC-) protection, SPIEZ LABORATORY deals with scientific and technical aspects of hazards associated with NBC incidents. In my talk I will present the various tasks of the four divisions of SPIEZ LABORATORY: Physics, Biology, Chemistry and NBC Protection. Special focus will be laid on the physics branch and the radioactivity group where I work on Gamma Spectrometry. The majority of natural radionuclides as well as most relevant fission and activation products emit gamma radiation. This makes gamma spectrometry a very important tool for nuclear forensics, field and sample measurements as well as for population monitoring both in case of normal and increased radiation levels. I will introduce the basic principles of this technique and report on the various fields of application established in our group.