ERIK MCLEAN / UNSPLASH

Physikalisches Kolloquium

Freitag, 17. Mai 2024 17:00 Uhr  Particle accelerator on a nanophotonic chip

Prof. Dr. Peter Hommelhoff, Institut für Physik der Kondensierten Materie, Universität Erlangen Particle accelerators are ubiquitous tools across scientific, industrial, and medical domains, pivotal not only in advancing particle physics but also in applications such as sterilization and radiotherapy in modern healthcare facilities. Traditionally, these accelerators harness microwave fields to impart momentum to swift electrons or other charged particles. Our research explores a paradigm shift, demonstrating the feasibility of employing laser light to achieve electron acceleration. Crucially, this approach necessitates structures capable of generating accelerating fields at the scale of the driving laser's wavelength – a scale substantially smaller than conventional accelerators, on the order of microns. Leveraging advancements in nanofabrication, we have developed the nanophotonic counterpart of an accelerator, enabling the acceleration of electrons through purely optical forces. A milestone achievement has been the realization of the electron "bucket," effectively confining and accelerating electrons within a 220nm narrow, 500 micron long accelerator channel. In our experiments, we have demonstrated electron acceleration from 28 keV to over 40 keV, marking significant progress towards compact and efficient light-driven electron devices. Furthermore, we explore intriguing phenomena arising from the natural bunching of electrons on attosecond timescales and the ability to shape individual electron wavepackets. These capabilities open new vistas for electron imaging, particularly in the realm of quantum mechanical phase imaging. In this presentation, we provide an overview of our experimental progress, offering insights into the potential of light-driven electron accelerator devices and electron wavepacket shaping and coupling.

Teilchenkolloquium

Simulation-Basted Inference Techniques and its....

Aishik Ghosh, LBL, Berkeley, CERN

Astronomisches Kolloquium

Dienstag, 21. Mai 2024 16:30 Uhr  Interchange magnetic reconnection as the driver of the fast solar wind

Professor James Drake, Institute for Physical Science and Technology, University of Maryland The mechanism that drives the solar wind has been a topic of extensive scientific debate since the 1960's when the existence of the solar wind was confirmed with spacecraft observations. In its recent closest approaches to the sun the Parker Solar Probe (PSP) spacecraft is revealing wind structure not seen by spacecraft at 1AU. The bursty radial flows and associated local reversals of the radial magnetic field (switchbacks) exhibit a spatial periodicity that is linked to that of network magnetic field near the solar surface (Bale et al. 2021; ApJ 923,174). The observations point to magnetic reconnection between open and closed magnetic flux in coronal holes (interchange reconnection) as the driver of these bursts. The corresponding enhancements in plasma pressure, wind speed, and energetic ions further suggest that interchange reconnection is the fundamental source of energy that drives the fast solar wind. We use the PSP data along with the basic characteristics of reconnection to deduce the local properties of interchange reconnection near the solar surface, including the characteristic strength of the reconnecting magnetic, the ambient density, the rate of reconnection and associated rate of energy release (Bale et al. 2023; Nature, vol. 628). An important conclusion of the analysis is that coronal interchange reconnection is in the collisionless regime and that the energy released by interchange reconnection is sufficient to drive the wind. Analytical estimates are supported by particle-in-cell simulations of interchange reconnection that establish that the structure of reconnection exhausts match PSP measurements. The spectra of energetic protons and alpha particles from the simulations, which take the form of powerlaws at high energy, also match the observations by the PSP. The bursty nature of interchange reconnection has implications for the development of the measured turbulence in the solar wind, which is currently being explored. These results have significant implications for understanding the winds produced by objects throughout the universe. Those unable to attend the colloquium in person are invited to participate online through Zoom (Meeting ID: 942 0262 2849, passcode 792771) using the link: https://eu02web.zoom-x.de/j/94202622849?pwd=dGlPQXBiUytzY1M2UE5oUDRhbzNOZz09 During his visit to Heidelberg, Professor Drake will be available for meetings by arrangement with his host, Brian Reville (brian.reville@mpi-hd.mpg.de)

Zentrum für Quantendynamik Kolloquium

Mittwoch, 22. Mai 2024 16:30 Uhr  Dissipation in Bose-Einstein Condensates

Prof. Dr. Herwig Ott, Fachbereich Physik, TU Kaiserslautern