A5103070116- Magnetic confinement fusion research
- Fusion materials and technologies
- Superconducting Materials and Applications
- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Solar and Space Plasma Dynamics
- Laser-Plasma Interactions and Diagnostics
- Ionosphere and magnetosphere dynamics
- Nuclear reactor physics and engineering
- Particle Detector Development and Performance
- Laser-induced spectroscopy and plasma
- Nuclear Physics and Applications
- Particle Accelerators and Free-Electron Lasers
- High-Energy Particle Collisions Research
- Rocket and propulsion systems research
- Atomic and Subatomic Physics Research
- Electrostatic Discharge in Electronics
- Carbon dioxide utilization in catalysis
- Nonlinear Dynamics and Pattern Formation
- Dark Matter and Cosmic Phenomena
- Historical and Environmental Studies
- Urban Planning and Valuation
- Semiconductor materials and devices
- Chemistry and Chemical Engineering
- Medical Imaging Techniques and Applications
Max Planck Institute for Plasma Physics - Greifswald
2018-2024
Max Planck Institute for Plasma Physics
2017-2022
Max Planck Society
2017-2021
Robert Bosch (Germany)
2021
University of Padua
2015-2018
Wendelstein 7-X is the first comprehensively optimized stellarator aiming at good confinement with plasma parameters relevant to a future power plant. Plasma operation started in 2015 using limiter configuration. After installing an uncooled magnetic island divertor, extending energy limit from 4 80 MJ, continued 2017. For this phase, electron cyclotron resonance heating (ECRH) capability was extended 7 MW, and hydrogen pellet injection implemented. The enhancements resulted highest triple...
Abstract We present novel experimental evidence of parametric decay instability microwave beams in the plasma edge Wendelstein 7-X stellarator. propose that is sustained by trapping only one daughter wave non-monotonic density profile measured with high spatial resolution within a stationary magnetic island. The power levels and spectral shapes detected signal are reproduced numerical modelling theoretical threshold predicted around 300 kW, comparable observations. predict fraction drained...
For stellarators, which need no or only small amounts of current drive, electron-cyclotron-resonance heating (ECRH) is a promising method even for the envisaged application in fusion power plant. Wendelstein 7-X (W7-X) equipped with steady-state capable ECRH system, operating at 140 GHz, corresponds to 2nd cyclotron harmonic electrons magnetic field 2.5 T. Ten gyrotrons are operational and already delivered 7 MW W7-X plasmas. Combined pellet injection, highest triple product (0.68 × 1020 keV...
The paper presents experimental observations and simulations for the effects of toroidal plasma current on divertor power depositions W7-X.With increasing accompanying changes in island geometry result a sweep strike line redistribution heat flux footprints.Good agreement between experiments, which partly used electron cyclotron drive to generate an additional contribution, modelling using field tracing vacuum magnetic fields including ad-hoc axis is found both standard low-iota configurations.
Abstract The optimised superconducting stellarator W7-X generates its rotational transform by means of external coils, therefore no toroidal current is necessary for plasma confinement. Electron cyclotron drive experiments were conducted strikeline control and safe divertor operation. During periodic repetitive crashes the central electron temperature, similar to sawtooth in tokamaks, detected. Measurements from soft x-ray tomography emission show that are preceded weak oscillating...
Abstract Sawtooth oscillations in tokamaks frequently lead to the redistribution of energetic ions, mainly on passing orbits, causing their expulsion from core. This paper discusses first measurements interaction fast ions and sawteeth Large Helical Device. The crashes were caused by plasma current induced Electron Cyclotron Current Drive Neutral Beam Drive. Despite these crashes, there was no detectable effect either core or at edge plasma.
Abstract In the Wendelstein 7-X (W7-X) stellarator, vacuum rotational transform, ι , has a flat radial profile and does not cross any major rational resonance. Nevertheless, during plasma operation ‐profile can be strongly modified by electron cyclotron current drive in such way that resulting -profile passes through low-order values, this trigger magnetohydrodynamic (MHD) events. Indeed, W7-X plasmas are sometimes subject to repetitive collapses of core confinement, which observed...
Numerical calculations based on nonlinear two-fluid equations have been carried out to understand the sawtooth-like crashes of electron temperature observed in Wendelstein 7-X stellarator experiments with cyclotron current drive (ECCD).The application ECCD leads nonmonotonic radial profiles safety factor q two q=1 surfaces plasma core region.Using input parameters similar experiment, numerical show types central depending growth internal kink mode coupled double tearing modes.When distance...
In its second operation phase (OP1.2a) W7-X was equipped with full 3d island divertor and an upgraded ECRH-system of 10 gyrotrons a total port through power 7 MW. The combination pellet fueling high density ECRH enabled to explore above 1 20 m -3 . particular the O2-polarisation combined multi-pass reflector tile system up 1.4 achieved. At slightly lower densities core beta values record fusion tripple product 0.66 keVs for stellarators were reached. addition routine plasma start-up wall...
This paper presents an overview of recent hardware extensions and data analysis developments to the Wendelstein 7-X visible core spectroscopy systems. These include upgrades prepare in-vessel components for long-pulse operation, nine additional spectrometers, a new line sight array passive spectroscopy, coherence imaging charge exchange diagnostic. Progress in includes ion temperatures densities from multiple impurity species, statistical comparison with x-ray crystal spectrometer...
Abstract Magnetic reconnection in W7-X is studied by means of global numerical simulations a series models increasing complexity. The magnetic geometry ranges from that cylinder to the full three-dimensional field W7-X, and equations solved range ideal magnetohydrodynamics (MHD) gyrokinetics. We simulate plasmas first operation phase with electron cyclotron current drive (ECCD). These are characterized an equilibrium featuring ECCD-distorted ‘humped’ profile rotational transform ι , = 1 two...
Sawtooth-like crashes were observed during electron cyclotron current drive experiments for strikeline controls at the optimised superconducting stellarator Wendelstein 7-X (W7-X). The majority of did not have a relevant impact on plasma performance. However, limited number events, characterised by large volume affected instability, been related to strong deterioration performance and even premature termination plasma. hot core expelled these sawtooth can reach edge, where surface...
To study and optimize negative ion production acceleration, in view of the use neutral beam injectors ITER project, SPIDER test facility (particle energy 100keV; current 50A, distributed over 1280 beamlets) is under construction Padova, with aim testing characteristics to verify source proper operation, by means several diagnostic systems. An array tungsten wires, directly exposed consequently heated high temperature, used similar experiments at IPP-Garching optics, which one most important...
The NIO1 experiment, built and operated at Consorzio RFX, hosts an RF negative ion source, from which it is possible to produce a beam of maximum 130 mA in H− ions, accelerated up 60 kV. For the preliminary tests extraction system source has been oxygen, whose high electronegativity allows reach useful levels extracted current. efficiency ions strongly influenced by electron density temperature close Plasma Grid, i.e. grid acceleration faces source. To support tests, these parameters have...
In the Wendelstein 7-X stellarator, up to 7MW of power are delivered plasma by an electron cyclotron resonance heating system consisting ten 140 GHz gyrotrons [1]. Due flexible front steering mirror each beam line, deposition can be varied over whole radius and is optionally combinable with additional current drive. This flexibility, together small toroidal currents in makes W7-X a perfect testbed for drive (ECCD) experiments, which have been successfully accomplished during first two...
Abstract Sawtooth crashes are observed during ECCD experiments at the superconducting optimized stellarator Wendelstein 7-X. The study and characterization necessary in order to understand under which condition can be driven without posing a risk experimental operations. development of automatic tools is crucial speed up analysis extensive datasets. In this work, we report on first attempt using data-driven approach automatically characterize sawtooth crashes. Cluster algorithms applied...
Abstract The rotational transform plays a crucial role in magnetic confinement devices and its profile is directly related to stability properties. A popular way assess the using Motional Stark Effect diagnostic system, which relies on splitting of Balmer alpha emission, due interaction between particle beam plasma. prototype was installed at stellarator Wendelstein 7-X, order demonstrate that such can be operated this device. This work presents design preliminary measurements as well...
After installation of Mo liners in the source NIO1 (Negative Ion Optimization phase 1), hydrogen plasmas a continuous regime operation (much longer than one hour) are routinely maintained, with more 1 kW rf power and 0.5 Pa pressure, allowing systematic investigation pure H− volume effect, which requests much lower acceleration voltage Vs ≅ 12 kV future Cs operations at 60 kV. A new extraction grid EG was installed (replacing some eroded insulators) preliminary beam images compared to old...
Abstract Detecting changes in plasmas is compulsory for control and the detection of novelties. Moreover, automated novelty allows one to investigate large data sets substantially enhance efficiency mining approaches. To this end we introduce permutation entropy (PE) plasmas. PE an information-theoretic complexity measure based fluctuation analysis that quantifies degree randomness (resp. disorder, unpredictability) ordering time series data. This method computationally fast robust against...