A5062480303- Magnetic confinement fusion research
- Ionosphere and magnetosphere dynamics
- Solar and Space Plasma Dynamics
- Particle accelerators and beam dynamics
- Fusion materials and technologies
- Superconducting Materials and Applications
- Plasma Diagnostics and Applications
- Laser-Plasma Interactions and Diagnostics
- Nuclear Physics and Applications
- Spacecraft and Cryogenic Technologies
- Laser-induced spectroscopy and plasma
- Geophysics and Gravity Measurements
- Stellar, planetary, and galactic studies
- Inorganic Fluorides and Related Compounds
- Astronomical Observations and Instrumentation
- Atomic and Molecular Physics
- Fluid Dynamics and Turbulent Flows
- Dust and Plasma Wave Phenomena
- Advanced Thermodynamic Systems and Engines
- Inorganic Chemistry and Materials
- Scientific Research and Discoveries
- Atomic and Subatomic Physics Research
- Magneto-Optical Properties and Applications
- Adaptive optics and wavefront sensing
- Calibration and Measurement Techniques
Max Planck Institute for Plasma Physics - Greifswald
2016-2024
Max Planck Society
2016-2021
Max Planck Institute for Plasma Physics
2016-2021
National Institute for Fusion Science
2016-2018
Princeton Plasma Physics Laboratory
2016-2018
The Graduate University for Advanced Studies, SOKENDAI
2018
Auburn University
2018
University of Maryland, College Park
2018
Kyoto University
2015-2016
Australian National University
2016
After completing the main construction phase of Wendelstein 7-X (W7-X) and successfully commissioning device, first plasma operation started at end 2015. Integral start-up using electron cyclotron resonance heating (ECRH) an extensive set diagnostics have been completed, allowing initial physics studies during operational campaign. Both in helium hydrogen, breakdown was easily achieved. Gaining experience with vessel conditioning, discharge lengths could be extended gradually. Eventually,...
The optimized, superconducting stellarator Wendelstein 7-X went into operation and delivered first measurement data after 15 years of construction one year commissioning. Errors in the magnet assembly were confirmend to be small. Plasma was started with 5 MW electron cyclotron resonance heating (ECRH) power five inboard limiters. Core plasma values keV, keV at line-integrated densities achieved, exceeding original expectations by about a factor two. Indications for core-electron-root found....
The results from the investigation of neoclassical core transport and role radial electric field profile (Er) in first operational phase Wendelstein 7-X (W7-X) stellarator are presented. In plasmas, details Er expected to have a strong effect on both particle heat fluxes. Investigation is important understanding validation calculations. closely related perpendicular plasma flow (u⊥) through force balance equation. This allows be inferred measurements velocity, which can measured using x-ray...
Abstract This research investigates the temporal evolution of toroidal plasma current in Wendelstein 7-X (W7-X) stellarator under different heating, fueling, and drive scenarios. The THRIFT code has been modernized its predictions have compared against experimentally measured currents W7-X. Good agreement is found with respect to characteristic timescale between simulated currents. total bootstrap under-predicted owing applicability BOOTSJ model for collisionalities question. Edge...
Wendelstein 7-X, a superconducting optimized stellarator built in Greifswald/Germany, started its first plasmas with the last closed flux surface (LCFS) defined by 5 uncooled graphite limiters December 2015. At end of 10 weeks long experimental campaign (OP1.1) more than 20 independent diagnostic systems were operation, allowing detailed studies many interesting plasma phenomena. For example, fast neutral gas manometers supported video cameras (including one fast-frame camera frame rates...
Experiments of suppressing fast-ion-driven MHD instabilities such as energetic particle modes (EPMs) and global Alfvén eigenmodes (GAEs) have been made using a second harmonic x-mode electron cyclotron heating current drive (ECCD) in the helical-axis heliotron device, Heliotron J. ECCD experiments show that GAEs destabilized by fast ions neutral beam injection with observed frequency around 140 kHz are fully stabilized, EPMs 90 suppressed when EC-driven plasma flowing counter direction...
Gyrokinetic simulations of plasma microturbulence in the Helically Symmetric eXperiment are presented. Using profiles relevant to experimental operation, four dominant drift wave regimes observed ion wavenumber range, which identified as different flavors density-gradient-driven trapped electron modes. For most part, heat transport exhibits properties associated with turbulence driven by these types Additionally, long-wavelength, radially localized, nonlinearly excited coherent structures...
The ECE diagnostic at W7-X in its standard mode of operation measures X2 polarization with a 32 channel radiometer the frequency band around 140 GHz for central magnetic field 2.5T. is calibrated by noise source and overall system absolutely means hot-cold placed outside torus front Gaussian telescope optics identical geometry transmission line as it installed measurements plasma vessel. supplemented 16 zoom device 4 span higher resolution suitable radial range Michelson interferometer...
Electron temperature gradient (ETG)-driven turbulence, despite its ultrafine scale, is thought to drive significant thermal losses in magnetic fusion devices-but what role does it play stellarators? The first numerical simulations of ETG turbulence for the Wendelstein 7-X stellarator, together with power balance analysis from initial experimental operation phase, suggest that associated transport should be negligible compared other channels. effect, we argue, originates essentially geometric...
The neutral beam deposition model in the BEAMS3D code is validated against attenuation data from Wendelstein 7-X (W7-X). A set of experimental discharges where injection system W7-X was utilized were reconstructed. These scanned magnetic configurations and plasma densities W7-X. equilibrium reconstructions performed using STELLOPT which calculates three-dimensional self-consistent ideal magnetohydrodynamic equilibria kinetic profiles. leveraged new capabilities to incorporate electron...
Abstract In the previous divertor campaign, Wendelstein 7-X (W7-X) device injected 3.6 MW of neutral beam heating power allowing for achievement densities approaching 2 × 10 20 m −3 , and providing first initial assessment fast ion confinement in a drift optimized stellarator. The injection (NBI) system on W7-X is comprised two boxes with space four radio frequency sources each. reported this work was achieved NI21 box. effect combined electron-cyclotron resonance (ECRH) NBI explored through...
This paper reports about a novel approach to the absolute intensity calibration of an electron cyclotron emission (ECE) spectroscopy system. Typically, ECE radiometer consists tens separated frequency channels corresponding different plasma locations. An overall diagnostic including near optics and transmission line is achieved with blackbody sources at LN2 temperature room via hot/cold mirror unit. As thermal source typically few thousand times lower than receiver noise temperature,...
Abstract The effect of electron cyclotron heating (ECH) and current drive (ECCD) on energetic-particle (EP)-driven magnetohydrodynamic (MHD) modes is studied in the helical devices LHD, TJ-II Heliotron J. We demonstrate that EP-driven MHD modes, including Alfvén eigenmodes (AEs) energetic particle (EPMs), can be controlled by ECH/ECCD. In LHD device, which has a moderate rotational transform high magnetic shear, co-ECCD enhances toroidal AEs (TAEs) global (GAEs), while counter-ECCD...
Abstract In electron (cyclotron) heated plasmas, in both ASDEX Upgrade ( L -mode) and Wendelstein 7-X, clamping of the ion temperature occurs at T i ∼ 1.5 keV independent magnetic configuration. The ions such plasmas are through energy exchange power as <?CDATA ${n}_{\mathrm{e}}^{2}({T}_{\mathrm{e}}-{T}_{\mathrm{i}})/{T}_{\mathrm{e}}^{3/2}$?> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>n</mml:mi> </mml:mrow>...
The role of the radial electric field in high-performance ion-root plasmas on Wendelstein 7-X (W7-X) is examined and compared with neoclassical predictions. W7-X stellarator world's first large-scale optimized stellarator. One important targets chosen for optimization during design process was reduction core heat transport. This targeted reactor-relevant high-density which ambipolar expected to be negative throughout core.
Observations on confinement in the first experimental campaign optimized Stellarator Wendelstein 7-X are summarized. In this phase W7-X was equipped with five inboard limiters only and thus discharge length restricted to avoid local overheating. Stationary plasmas limited low densities <2–3 · 1019 m−3. With available 4.3 MW ECR Heating core Te ~ 8 keV, Ti 1–2 keV achieved routinely resulting energy time τE between 80 ms 150 ms. For these conditions show characteristics of electron root...
Second harmonic electron cyclotron current drive (ECCD) has been applied in the stellarator/heliotron (S/H) device, Heliotron J, to stabilize magnetohydrodynamic (MHD) modes. The energetic particle mode (EPM) of 60–90 kHz frequency, one energetic-ion-driven MHD modes, is excited a plasma heated by co- and counter-neutral beam injection heating (ECH). EPM stabilized counter-ECCD which decreases rotational transform. Localized EC driven few kA at central region modifies transform profile,...
In this work we present the first measurements obtained by V-band Doppler reflectometer during second operation phase of Wendelstein 7-X to discuss influence in velocity shear layer and radial electric field, Er, several plasma parameters such as magnetic configuration, rotational transform or degree detachment. place, carry out a systematic characterization turbulence rotation profile order describe density heating power on Er under four most frequent configurations. The E value edge is...
Abstract When realising future fusion reactors, their stationary burning must be maintained and the heat flux to divertor reduced. This essentially requires a internal transport barrier (ITB) plasma with fast control system. However, time scale for determining position of foot point an ITB is not clearly understood even though its understanding indispensable profile control. In this study, electron (eITB) was observed reformed at vicinity magnetic island when started form. addition, enhanced...
Stiffness measurements are presented in the quasi-helically symmetric experiment (HSX), which neoclassical transport is comparable to that a tokamak and turbulent dominates throughout plasma. Electron cyclotron emission used measure local electron temperature response modulated resonant heating. The amplitude phase of heat wave through steep gradient (ETG) region plasma determine transient thermal diffusivity close steady-state diffusivity. low stiffness between 0.2 ≤ r/a 0.4 agrees with...
In the Wendelstein 7-X magnetic confinement experiment, a reduction of turbulent density fluctuations as well anomalous impurity diffusion is associated with peaking plasma profile. These effects correlate improved and appear largely due to transport change in neoclassical small. The observed decrease heat flux increased gradients agreement nonlinear gyrokinetic simulations, has been attributed unique geometry W7-X that limits severity trapped electron modes.
Abstract The W7-X stellarator has so far performed experiments under both limiter and divertor conditions. plasma is mostly generated by ECR-heating with powers up to 6.5 MW, the density usually limited radiation losses from low-Z impurities (such as carbon oxygen) released mainly graphite targets. present work first summarizes loss fractions f rad achieved in quasi-stationary hydrogen plasmas operational phases, then shows how impurity behaves differently two different boundary conditions...
The formation of an electron internal transport barrier (eITB) has been observed for the first time with centrally focused cyclotron heating (ECH) microwaves injected into plasma in Heliotron J. When power per density () exceeds a threshold , transient increases both central Te and core gradients are observed. A neoclassical (NC) calculation using Sugama–Nishimura moment method predicts that large positive radial electric field (Er) is formed region. Heat analysis shows significant reduction...
A new far infrared (FIR) laser interferometer with high time resolution has been developed in Heliotron J for measuring performance plasmas. The FIR is a heterodyne-type Michelson 1 MHz intermediate frequency. uses super rotating grating and the viewing chord passes through an off-axis position. Refraction density plasma estimated using TRAVIS ray-tracing code. results suggest that it possible to extend range of up 1.5×1020 m−3. first line-averaged measurements have made ECH NBI heated...