33 research outputs found
Joining by forming technologies: current solutions and future trends
The progressively more demanding needs of emissions and costs reduction in the transportation industry are pushing engineers towards the use of increasingly lightweight structures. This goal can be achieved only if dissimilar and/or new materials, including polymers and composites, are joined together to create complex structures. Conventional fusion welding processes have often been proven inadequate to this task because of the high heat input reducing the joint mechanical properties or even making the joining process impossible. Joining by forming technologies take advantage on the plastic deformation to create sound joints out of even very dissimilar materials. Over the last 25 years, several new processes, with increasing potential in effectively joining virtually every structural material, have been invented and developed. In the paper, a comprehensive overview of the most utilized joining by forming processes is given. For each process, an analysis of the current research trends and hot topics is provided, highlighting strengths and weaknesses for industrial applications
Phase cycling of extreme ultraviolet pulse sequences generated in rare gases
The development of schemes for coherent nonlinear time-domain spectroscopy in the extreme-ultraviolet regime (XUV) has so far been impeded by experimental difficulties that arise at these short wavelengths. In this work we present a novel experimental approach, which facilitates the timing control and phase cycling of XUV pulse sequences produced by harmonic generation in rare gases. The method is demonstrated for the generation and high spectral resolution characterization of narrow-bandwidth harmonics (≈14 eV) in argon and krypton. Our technique simultaneously provides high phase stability and a pathway-selective detection scheme for nonlinear signals—both necessary prerequisites for all types of coherent nonlinear spectroscopy
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Phase cycling of extreme ultraviolet pulse sequences generated in rare gases
The development of schemes for coherent nonlinear time-domain spectroscopy in the extreme-ultraviolet regime (XUV) has so far been impeded by experimental difficulties that arise at these short wavelengths. In this work we present a novel experimental approach, which facilitates the timing control and phase cycling of XUV pulse sequences produced by harmonic generation in rare gases. The method is demonstrated for the generation and high spectral resolution characterization of narrow-bandwidth harmonics (˜14 eV) in argon and krypton. Our technique simultaneously provides high phase stability and a pathway-selective detection scheme for nonlinear signals - both necessary prerequisites for all types of coherent nonlinear spectroscopy. © 2020 The Author(s). Published by IOP Publishing Ltd on behalf of the Institute of Physics and Deutsche Physikalische Gesellschaft
Improved stabilization scheme for extreme ultraviolet quantum interference experiments
Interferometric pump-probe experiments in the extreme ultraviolet (XUV)
domain are experimentally very challenging due to the high phase stability
required between the XUV pulses. Recently, an efficient phase stabilization
scheme was introduced for seeded XUV free electron lasers (FELs) combining
shot-to-shot phase modulation with lock-in detection. This method stabilized
the seed laser beampath on the fundamental ultraviolet wavelength to a high
degree. Here, we extend this scheme including the stabilization of the XUV
beampath, incorporating phase fluctuations from the FEL high gain harmonic
generation process. Our analysis reveals a clear signal improvement with the
new method compared to the previous stabilization scheme
High-Gain Harmonic Generation with temporally overlapping seed pulses and application to ultrafast spectroscopy
Collinear double-pulse seeding of the High-Gain Harmonic Generation (HGHG)
process in a free-electron laser (FEL) is a promising approach to facilitate
various coherent nonlinear spectroscopy schemes in the extreme ultraviolet
(XUV) spectral range. However, in collinear arrangements using a single
nonlinear medium, temporally overlapping seed pulses may introduce nonlinear
mixing signals that compromise the experiment at short time delays. Here, we
investigate these effects in detail by extending the analysis described in a
recent publication (Wituschek et al., Nat. Commun., 11, 883, 2020). High-order
fringe-resolved autocorrelation and wave-packet interferometry experiments at
photon energies > eV are performed, accompanied by numerical simulations.
It turns out that both the autocorrelation and the wave-packet interferometry
data are very sensitive to saturation effects and can thus be used to
characterize saturation in the HGHG process. Our results further imply that
time-resolved spectroscopy experiments are feasible even for time delays
smaller than the seed pulse duration.Comment: This is accepted version of the article. The Version of Record is
available online at https://doi.org/10.1364/OE.40124
Extreme Ultraviolet Wave Packet Interferometry of the Autoionizing HeNe Dimer
Femtosecond extreme ultraviolet wave packet interferometry (XUV-WPI) was applied to study resonant interatomic Coulombic decay (ICD) in the HeNe dimer. The high demands on phase stability and sensitivity for vibronic XUV-WPI of molecular-beam targets are met using an XUV phase-cycling scheme. The detected quantum interferences exhibit vibronic dephasing and rephasing signatures along with an ultrafast decoherence assigned to the ICD process. A Fourier analysis reveals the molecular absorption spectrum with high resolution. The demonstrated experiment shows a promising route for the real-time analysis of ultrafast ICD processes with both high temporal and high spectral resolution
The influence of axial magnetic fields on the extraction of an ion beam from a plasma source
Modifikation einer Ionenquelle zur ionenstrahlgestuetzten Beschichtung von Bauteilen
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Wirkungen einer Reform der Einkommensfoerderung nach dem Berlinfoerderungsgesetz auf ihre Adressaten und die oeffentlichen Haushalte: Gutachten im Auftrag der Fraktion Alternative Liste im Abgeordnetenhaus von Berlin (W)
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