T. Wegner
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View article: Impurity transport study based on measurement of visible wavelength high-n charge exchange transitions at W7-X
Impurity transport study based on measurement of visible wavelength high-n charge exchange transitions at W7-X Open
A recently installed high-speed charge exchange diagnostic at the W7-X stellarator has been used to identify several high-n Rydberg emission lines near 500 nm following impurity injections. The wavelengths of observed high-n Rydberg transi…
View article: Achieving stationary high performance plasmas at Wendelstein 7-X
Achieving stationary high performance plasmas at Wendelstein 7-X Open
This work reports on recent results on the search for high performance plasma scenarios at the magnetically confined stellarator fusion device Wendelstein 7-X. In four new designed scenarios, the development from transient toward stationar…
View article: Performance of tungsten plasma facing components in the stellarator experiment W7-X: Recent results from the first OP2 campaign
Performance of tungsten plasma facing components in the stellarator experiment W7-X: Recent results from the first OP2 campaign Open
The transition to reactor-relevant materials for the plasma facing components (PFCs) is an important and necessary step to provide a proof of principle that the stellarator concept can meet the requirements of a future fusion reactor by de…
View article: Observation of impurity accumulation and its compatibility with high plasma performance in W7-X
Observation of impurity accumulation and its compatibility with high plasma performance in W7-X Open
At the W7-X stellarator, the bolometer system has measured an intensive radiation zone in the inner plasma region (at a normalized radius ρ ∼ 0.3–0.4) in the hydrogen plasma generated by electron cyclotron resonance heating; it differs fro…
View article: Quantitative comparison of impurity transport in turbulence reduced and enhanced scenarios at Wendelstein 7-X
Quantitative comparison of impurity transport in turbulence reduced and enhanced scenarios at Wendelstein 7-X Open
We assess the turbulent particle transport being responsible for the limitation of the confinement and, thus, the overall performance of the neoclassically optimized stellarator Wendelstein 7-X. The radial particle transport is experimenta…
View article: Overview of core impurity transport in the first divertor operation of Wendelstein 7-X
Overview of core impurity transport in the first divertor operation of Wendelstein 7-X Open
The impurity transport at Wendelstein 7-X during its most recent campaign is characterized and documented for a variety of different plasma scenarios. An overview of its dependence on several quantities is given, which allows identificatio…
View article: Development of a new manipulator for the laser blow-off system at Wendelstein 7-X
Development of a new manipulator for the laser blow-off system at Wendelstein 7-X Open
A new manipulator for the existing laser blow-off system, being applied for impurity transport studies, was designed and is installed at Wendelstein 7-X stellarator. The proper choice of suitable materials in combination with a sophisticat…
View article: Design of a new charge exchange recombination spectroscopy diagnostic for impurity transport experiments at Wendelstein 7-X
Design of a new charge exchange recombination spectroscopy diagnostic for impurity transport experiments at Wendelstein 7-X Open
In this study, we present the design of a new charge exchange recombination spectroscopy (CXRS) system for Wendelstein 7-X (W7-X), which aims at measuring line radiation from highly ionized iron impurities after laser blow off injections o…
View article: Confinement in electron heated plasmas in Wendelstein 7-X and ASDEX Upgrade; the necessity to control turbulent transport
Confinement in electron heated plasmas in Wendelstein 7-X and ASDEX Upgrade; the necessity to control turbulent transport Open
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 of magnetic configuration. The ions in such plasmas are heated through the en…
View article: Impurity transport in ion- and electron-root confinement scenarios at Wendelstein 7-X
Impurity transport in ion- and electron-root confinement scenarios at Wendelstein 7-X Open
This paper reports on the observation of enhanced Ar impurity confinement in high density, turbulence reduced ion-root confinement (IRC) scenarios in Wendelstein 7-X (W7-X). Compared to the central electron-root confinement (CERC), Ar dens…
View article: First neutral beam experiments on Wendelstein 7-X
First neutral beam experiments on Wendelstein 7-X Open
| openaire: EC/H2020/633053/EU//EUROfusion
View article: Suppression of core turbulence by profile shaping in Wendelstein 7-X
Suppression of core turbulence by profile shaping in Wendelstein 7-X Open
In the Wendelstein 7-X magnetic confinement experiment, a reduction of turbulent density fluctuations as well as anomalous impurity diffusion is associated with a peaking of the plasma density profile. These effects correlate with improved…
View article: Publisher’s Note: “Preparation, analysis, and application of coated glass targets for the Wendelstein 7-X laser blow-off system” [Rev. Sci. Instrum. 91, 083503 (2020)]
Publisher’s Note: “Preparation, analysis, and application of coated glass targets for the Wendelstein 7-X laser blow-off system” [Rev. Sci. Instrum. 91, 083503 (2020)] Open
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View article: Preparation, analysis, and application of coated glass targets for the Wendelstein 7-X laser blow-off system
Preparation, analysis, and application of coated glass targets for the Wendelstein 7-X laser blow-off system Open
Coated glass targets are a key component of the Wendelstein 7-X laser blow-off system that is used for impurity transport studies. The preparation and analysis of these glass targets as well as their performance is examined in this paper. …
View article: Charge-state independent anomalous transport for a wide range of different impurity species observed at Wendelstein 7-X
Charge-state independent anomalous transport for a wide range of different impurity species observed at Wendelstein 7-X Open
In this paper, the plasma volume averaged impurity confinement of selected charge states and impurity species has been characterized for the Stellarator Wendelstein 7-X (W7-X), covering a wide range of atomic charges (Z = 12–44) and atomic…
View article: Charge exchange recombination spectroscopy at Wendelstein 7-X
Charge exchange recombination spectroscopy at Wendelstein 7-X Open
The Charge Exchange Recombination Spectroscopy (CXRS) diagnostic has become a routine diagnostic on almost all major high temperature fusion experimental devices. For the optimized stellarator Wendelstein 7-X (W7-X), a highly flexible and …
View article: Overview of first Wendelstein 7-X high-performance operation
Overview of first Wendelstein 7-X high-performance operation Open
The optimized superconducting stellarator device Wendelstein 7-X (with major radius , minor radius , and plasma volume) restarted operation after the assembly of a graphite heat shield and 10 inertially cooled island divertor modules. This…
View article: Impurity transport studies at Wendelstein 7-X by means of x-ray imaging spectrometer measurements
Impurity transport studies at Wendelstein 7-X by means of x-ray imaging spectrometer measurements Open
This study reports on the effect of on- and off-axis heating power deposition on the impurity confinement in purely electron cyclotron resonance heated He plasmas on the stellarator Wendelstein 7-X. Therefore, impurity transport times τ I …
View article: Plasma impurities observed by a pulse height analysis diagnostic during the divertor campaign of the Wendelstein 7-X stellarator
Plasma impurities observed by a pulse height analysis diagnostic during the divertor campaign of the Wendelstein 7-X stellarator Open
The paper reports on the optimization process of the soft X-ray pulse height analyzer installed on the Wendelstein 7-X (W7-X) stellarator. It is a 3-channel system that records X-ray spectra in the range from 0.6 to 19.6 keV. X-ray spectra…
View article: Prospects of X-ray imaging spectrometers for impurity transport: Recent results from the stellarator Wendelstein 7-X (invited)
Prospects of X-ray imaging spectrometers for impurity transport: Recent results from the stellarator Wendelstein 7-X (invited) Open
This paper reports on the design and the performance of the recently upgraded X-ray imaging spectrometer systems, X-ray imaging crystal spectrometer and high resolution X-ray imaging spectrometer, installed at the optimized stellarator Wen…
View article: Design, capabilities, and first results of the new laser blow-off system on Wendelstein 7-X
Design, capabilities, and first results of the new laser blow-off system on Wendelstein 7-X Open
We present a detailed overview and first results of the new laser blow-off system on the stellarator Wendelstein 7-X. The system allows impurity transport studies by the repetitive and controlled injection of different tracer ions into the…
View article: On the E-H transition in inductively coupled radio frequency oxygen plasmas: II. Electronegativity and the impact on particle kinetics
On the E-H transition in inductively coupled radio frequency oxygen plasmas: II. Electronegativity and the impact on particle kinetics Open
In this series of two papers we present results about the E-H transition of an inductively coupled oxygen discharge driven at radio frequency (13.56 MHz) for different total gas pressures. The mode transition from the low density E-mode to…
View article: On the E-H transition in inductively coupled radio frequency oxygen plasmas: I. Density and temperature of electrons, ground state and singlet metastable molecular oxygen
On the E-H transition in inductively coupled radio frequency oxygen plasmas: I. Density and temperature of electrons, ground state and singlet metastable molecular oxygen Open
In this series of two papers, the E-H transition in a planar inductively coupled radio frequency discharge (13.56 MHz) in pure oxygen is studied using comprehensive plasma diagnostic methods. The electron density serves as the main plasma …