Aging effects manifested in the potential energy landscape of a model glass former

We present molecular dynamics simulations of a model glass-forming liquid (the binary Kob-Anderson Lennard-Jones model) and consider the distributions of inherent energies and metabasins during aging. In addition to the typical protocol of performing a temperature jump from a high temperature to a low destination temperature, we consider the temporal evolution of the distributions after an 'up-jump', i.e. from a low to a high temperature. In this case the distribution of megabasin energies exhibits a transient two-peak structure. Our results can qualitatively be rationalized in terms of a trap model with a Gaussian distribution of trap energies. The analysis is performed for different system sizes. A detailed comparison with the trap model is possible only for a small system because of major averging effects for larger systems.Comment: 16 pages, 14 figure

Efficient laser-driven proton acceleration from cylindrical and planar cryogenic hydrogen jets.

We report on recent experimental results deploying a continuous cryogenic hydrogen jet as a debris-free, renewable laser-driven source of pure proton beams generated at the 150 TW ultrashort pulse laser Draco. Efficient proton acceleration reaching cut-off energies of up to 20 MeV with particle numbers exceeding 109 particles per MeV per steradian is demonstrated, showing for the first time that the acceleration performance is comparable to solid foil targets with thicknesses in the micrometer range. Two different target geometries are presented and their proton beam deliverance characterized: cylindrical (∅ 5 μm) and planar (20 μm × 2 μm). In both cases typical Target Normal Sheath Acceleration emission patterns with exponential proton energy spectra are detected. Significantly higher proton numbers in laser-forward direction are observed when deploying the planar jet as compared to the cylindrical jet case. This is confirmed by two-dimensional Particle-in-Cell (2D3V PIC) simulations, which demonstrate that the planar jet proves favorable as its geometry leads to more optimized acceleration conditions

Observation of ultrafast solid-density plasma dynamics using femtosecond X-ray pulses from a free-electron laser

The complex physics of the interaction between short pulse high intensity lasers and solids is so far hardly accessible by experiments. As a result of missing experimental capabilities to probe the complex electron dynamics and competing instabilities, this impedes the development of compact laser-based next generation secondary radiation sources, e.g. for tumor therapy [Bulanov2002,ledingham2007], laboratory-astrophysics [Remington1999,Bulanov2015], and fusion [Tabak2014]. At present, the fundamental plasma dynamics that occur at the nanometer and femtosecond scales during the laser-solid interaction can only be elucidated by simulations. Here we show experimentally that small angle X-ray scattering of femtosecond X-ray free-electron laser pulses facilitates new capabilities for direct in-situ characterization of intense short-pulse laser plasma interaction at solid density that allows simultaneous nanometer spatial and femtosecond temporal resolution, directly verifying numerical simulations of the electron density dynamics during the short pulse high intensity laser irradiation of a solid density target. For laser-driven grating targets, we measure the solid density plasma expansion and observe the generation of a transient grating structure in front of the pre-inscribed grating, due to plasma expansion, which is an hitherto unknown effect. We expect that our results will pave the way for novel time-resolved studies, guiding the development of future laser-driven particle and photon sources from solid targets

Observation of Ultrafast Solid-Density Plasma Dynamics Using Femtosecond X-Ray Pulses from a Free-Electron Laser

The complex physics of the interaction between short-pulse ultrahigh-intensity lasers and solids is so far difficult to access experimentally, and the development of compact laser-based next-generation secondary radiation sources, e.g., for tumor therapy, laboratory astrophysics, and fusion, is hindered by the lack of diagnostic capabilities to probe the complex electron dynamics and competing instabilities. At present, the fundamental plasma dynamics that occur at the nanometer and femtosecond scales during the laser-solid interaction can only be elucidated by simulations. Here we show experimentally that small-angle x-ray scattering of femtosecond x-ray free-electron laser pulses facilitates new capabilities for direct in situ characterization of intense short-pulse laser-plasma interactions at solid density that allows simultaneous nanometer spatial and femtosecond temporal resolution, directly verifying numerical simulations of the electron density dynamics during the short-pulse high-intensity laser irradiation of a solid density target. For laser-driven grating targets, we measure the solid density plasma expansion and observe the generation of a transient grating structure in front of the preinscribed grating, due to plasma expansion. The density maxima are interleaved, forming a double frequency grating in x-ray free-electron laser projection for a short time, which is a hitherto unknown effect. We expect that our results will pave the way for novel time-resolved studies, guiding the development of future laser-driven particle and photon sources from solid targets

Efficient laser-driven proton acceleration from cylindrical and planar cryogenic hydrogen jets

We report on recent experimental results deploying a continuous cryogenic hydrogen jet as a debris-free, renewable laser-driven source of pure proton beams generated at the 150 TW ultrashort pulse laser Draco. Efficient proton acceleration reaching cut-off energies of up to 20 MeV with particle numbers exceeding 109 particles per MeV per steradian is demonstrated, showing for the first time that the acceleration performance is comparable to solid foil targets with thicknesses in the micrometer range. Two different target geometries are presented and their proton beam deliverance characterized: cylindrical (∅ 5 μm) and planar (20 μm × 2 μm). In both cases typical Target Normal Sheath Acceleration emission patterns with exponential proton energy spectra are detected. Significantly higher proton numbers in laser-forward direction are observed when deploying the planar jet as compared to the cylindrical jet case. This is confirmed by two-dimensional Particle-in-Cell (2D3V PIC) simulations, which demonstrate that the planar jet proves favorable as its geometry leads to more optimized acceleration conditions

Untersuchung neuer Hinterkantenklappensysteme für Verkehrsflugzeuge

Die vorliegende Studienarbeit befasst sich mit der Untersuchung neuer Hinterkantenklappensysteme für Verkehrsflugzeuge in der anhand eines neu erstellten und verifizierten Simulinkmodells des ATTAS gezeigt wird, dass das Aufteilen eines Hinterkantenklappensystems in individuelle, stufenlosfahrbare Klappensegmente zu einem geringen Mehrnutzen im Bereich der Flugmechanik führt. Der erste Teilbereich der Arbeit befasst sich im allgemeinen mit Hochauftriebssystemen, in dem festgestellt wird, dass der Trend an der Hinterkante zu dem von Airbus favorisiertem Einfachspaltklappen mit Führungsmechanismus und an der Vorderkante zum Vorflügel mit drei Positionen geht. Des Weiteren wird der ATTAS und sein Hinterkantenklappensystem vorgestellt. Ein zweiter Teilbereich stellt die Erstellung, Verifizierung und Einbindung in eine Echtzeitumgebung des Simulinkmodells dar. Aus dem C-160 Basismodell und weiteren älteren Modellen wird ein neues ATTAS Modell erstellt, welches erfolgreich mit dem aus Flugversuchsdaten verifiziertem Simulamodell verglichen wird. In das erstellte ATTAS Modell wird ein neues Hinterkantenklappensystem mit jeweils zwei stufenlosausfahrbaren Segmenten pro Flügel integriert. Im dritten Bereich findet eine flugmechanische Untersuchung des neuen Klappensystems statt, in dem gezeigt wird, dass das System ein Potential an Mehrnutzen mit sich bringt, dieses a-ber nur durch eine Verbesserung der Stellgeschwindigkeiten erreicht werden kann. Des Weiteren würde eine Einbindung in den Autopiloten weitere wichtige Vorteile mit sich bringen

Nonlinear response from the perspective of energy landscapes and beyond

The paper discusses the nonlinear response of disordered systems. In particular we show how the nonlinear response can be interpreted in terms of properties of the potential energy landscape. It is shown why the use of relatively small systems is very helpful for this approach. For a standard model system we check which system sizes are particular suited. In case of the driving of a single particle via an external force the concept of an effective temperature helps to scale the force dependence for different temperature on a single master curve. In all cases the mobility increases with increasing external force. These results are compared with a stochastic process described by a 1d Langevin equation where a similar scaling is observed. Furthermore it is shown that for different classes of disordered systems the mobility can also decrease with increasing force. The results can be related to the properties of the chosen potential energy landscape. Finally, results for the crossover from the linear to the nonlinear conductivity of ionic liquids are presented, inspired by recent experimental results in the Roling group. Apart from a standard imidazolium-based ionic liquid we study a system which is characterized by a low conductivity as compared to other ionic liquids and very small nonlinear effects. We show via a real space structural analysis that for this system a particularly strong pair formation is observed and that the strength of the pair formation is insensitive to the application of strong electric fields. Consequences of this observation are discussed