A5045213160- Dust and Plasma Wave Phenomena
- Ionosphere and magnetosphere dynamics
- Magnetic confinement fusion research
- Cold Atom Physics and Bose-Einstein Condensates
- Laser-Plasma Interactions and Diagnostics
- High-pressure geophysics and materials
- Earthquake Detection and Analysis
- Fusion materials and technologies
- Solar and Space Plasma Dynamics
- Particle accelerators and beam dynamics
- Geomagnetism and Paleomagnetism Studies
- Laser-induced spectroscopy and plasma
- Superconducting Materials and Applications
- Astro and Planetary Science
- Statistical Mechanics and Entropy
- Astrophysics and Star Formation Studies
- Laser Design and Applications
- Quantum Electrodynamics and Casimir Effect
- Particle Dynamics in Fluid Flows
- Quantum, superfluid, helium dynamics
Max Planck Institute for Plasma Physics
2019-2021
Max Planck Institute for Plasma Physics - Greifswald
2019-2020
Max Planck Society
2019
Universität Greifswald
2013-2018
An imaging Mie scattering technique has been developed to measure the spatially resolved size distribution of dust particles in extended clouds. For large clouds micrometre-sized plastic confined an radio frequency (rf) discharge, a segmentation cloud into populations different sizes is observed, even though differences are very small. The dispersion inside population much smaller than difference between populations. Furthermore, found be constantly decreasing over time while inert argon...
Experiments on dust clusters trapped in the sheath of a radio frequency discharge have been performed for different magnetic field strengths ranging from few milliteslas to 5.8 T. The dynamics are analyzed terms their normal modes. From that, various properties such as kinetic temperature, charge, and screening length derived. It is found that temperature cluster rises with field, whereas charge nearly remains constant. increases slightly at intermediate strengths. Generally, seem correlate...
Experiments on self-excited dust-density waves under various magnetic fields have been performed. For that purpose, different dust clouds of micrometer-sized particles were trapped in the sheath a radio frequency discharge. The studied for field strengths ranging from 0 mT to about 2 T. It was observed are very coherent at lowest (B < 20 mT). At medium (20 B<300 mT), seem feature complex competition between wave modes before, even higher fields, become more again. highest...
The fundamentals of stereoscopy and their application to dusty plasmas are described. It is shown that stereoscopic methods allow us measure the three-dimensional particle positions trajectories with high spatial temporal resolution. underlying technical implications presented requirements limitations discussed. method demonstrated for dust particles in dust-density waves under microgravity conditions.
To improve the reliability of ASDEX pressure gauges in plasma vessel Wendelstein 7-X stellarator, nine them were equipped with a LaB6 crystal electron emitter for first time. These cathode operated during last campaign 2018 (operation phase 1.2b) only 2 A heating current over 40 h magnetic field about 2.1 T without failure. Owing to this excellent performance, we have decided equip all cathodes next 2). We report on pretest superconducting magnet, show measurement neutral 7-X, and...
The control of rotational transform in Wendelstein 7-X (W7-X) is key to both the island divertor operation and safety plasma facing components. concept W7-X relies on an edge flux surface with resonating intrinsic n/m = 5/5 resonance form a five lobed chain. This chain intersects plates give rise divertor. Changes relative position rational can result changes performance, thus essential device. During first campaign electromagnetic loads resulted elastic deformations shaped modular...
The quantities entropy and diffusion are measured for two- three-dimensional (3D) dust clusters in the fluid state. Entropy predicted to be closely linked via unstable modes. method of instantaneous normal modes is applied various laser-heated determine these corresponding diffusive properties. configurational 2D 3D from structural rearrangements. shows a threshold behavior at critical temperature clusters, allowing us estimate melting temperature. Further, entropic disorder increases larger...
Dust clusters of about 50–1000 particles have been confined near the sheath region a gaseous radio-frequency plasma discharge. These compact exhibit vortex motion which has reconstructed in full three dimensions from stereoscopy. Smaller are found to show competition between solid-like cluster structure and motion, whereas larger feature very pronounced vortices. From three-dimensional analysis, dust flow field be nearly incompressible. The vortices all observed essentially poloidal....
The spectral properties of three-dimensional dust clusters confined in gaseous discharges are investigated using both a fluid mode description and the normal analysis (NMA). modes analysed for crystalline as well laser-heated fluid-like clusters. It is shown that even with low particle numbers under presence damping can be identified. Laser-heating leads to excitation several, mainly transverse, modes. frequencies found nearly independent coupling parameter support predictions underlying...
The recrystallization process of finite three-dimensional dust clouds after laser heating is studied experimentally. time-dependent Coulomb coupling parameter presented, showing that the starts with an exponential cooling phase where slower than damping by neutral gas friction. At later times, oscillates into equilibrium. It found a large fraction cluster states experiments in metastable states. temporal evolution correlation buildup shows occurs on even time scale cooling.
The dynamic properties of finite three-dimensional dust clusters in a dusty plasma under the influence an ion focus are studied by normal modes. mode analysis has been extended to account for using point-charge model horizontal interaction particles. From that, analytical few-particle system is derived accounting three distinct dynamical regimes at different strengths, namely, absolutely unstable and fully stable configurations as well oscillatory regime. techniques (NMA) instantaneous modes...
Particle-containing (complex or dusty) plasmas offer and require the development of sophisticated diagnostic techniques to measure their properties such as particle motion, density, size demixing properties. Here, an overview selected optical for dusty some recent applications are given. As examples, angle-resolved tomography reveals spatially resolved density in dense dust systems well distribution particles trapped plasma. Phase separation binary mixtures can be studied by exploiting...
Abstract The investigation of fuel retention in fusion experiments is important view plasma density control as well tritium inventory for future reactors. We present a first gas balance the stellarator Wendelstein 7-X with its inertially cooled graphite divertor. used to estimate wall and it found that plays an dynamic role, absorbing or releasing particles depending on conditions. Several different scenarios are presented effect fueling heating assessed. find record duration experiment 100...
The phase transition of finite Yukawa balls (ordered systems microspheres in a gaseous plasma environment) with less than 100 particles is studied experimentally by means configurational entropies. We have developed cylindrical two- and three-particle-correlation functions to measure these entropies for multiple cluster sizes over wide temperature range. finely tuned using stochastic laser heating setup. It shown that the correlation give detailed insight into structural properties cluster....
The recrystallization process of a finite dust cloud is studied experimentally on the kinetic level. temporal evolution coupling parameter allows to reveal that cluster molten while laser heated and recrystallizes when heating switched OFF. cooling rate can be deduced from initial stage recrystallization.