H. Damm
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View article: Overview of the first Wendelstein 7-X long pulse campaign with fully water-cooled plasma facing components
Overview of the first Wendelstein 7-X long pulse campaign with fully water-cooled plasma facing components Open
After a long device enhancement phase, scientific operation resumed in 2022. The main new device components are the water cooling of all plasma facing components and the new water-cooled high heat flux divertor units. Water cooling allowed…
View article: Core Diagnostics for WENDELSTEIN 7-X Steady-State Exploration Until 18 GJ
Core Diagnostics for WENDELSTEIN 7-X Steady-State Exploration Until 18 GJ Open
This contribution provides an overview of the core diagnostics as they are required for W7-X steady-state high-density operation with a divertor and profile control. The inferred profiles then address the stellarator optimization. A partic…
View article: On the role of density fluctuations in the core turbulent transport of Wendelstein 7-X
On the role of density fluctuations in the core turbulent transport of Wendelstein 7-X Open
A recent characterization of core turbulence carried out with a Doppler reflectometer in the optimized stellarator Wendelstein 7-X (W7-X) found that discharges achieving high ion temperatures at the core featured an ITG-like suppression of…
View article: Experimental confirmation of efficient island divertor operation and successful neoclassical transport optimization in Wendelstein 7-X
Experimental confirmation of efficient island divertor operation and successful neoclassical transport optimization in Wendelstein 7-X Open
We present recent highlights from the most recent operation phases of Wendelstein 7-X, the most advanced stellarator in the world. Stable detachment with good particle exhaust, low impurity content, and energy confinement times exceeding 1…
View article: Bolometer tomography on Wendelstein 7-X for study of radiation asymmetry
Bolometer tomography on Wendelstein 7-X for study of radiation asymmetry Open
The algorithm for bolometer tomography at Wendelstein 7-X (W7-X) has been recently improved using a novel regularization functional, based on relative gradient smoothing (RGS) of the sought radiation profile. It has been validated using ra…
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: Impact of magnetic islands on plasma flow and turbulence in W7-X
Impact of magnetic islands on plasma flow and turbulence in W7-X Open
The effect of magnetic islands on plasma flow and turbulence has been experimentally investigated in the stellarator W7-X. Magnetic configurations with the 5/5 magnetic island positioned at the plasma edge, inside the last closed flux surf…
View article: Radial electric field and density fluctuations measured by Doppler reflectometry during the post-pellet enhanced confinement phase in W7-X
Radial electric field and density fluctuations measured by Doppler reflectometry during the post-pellet enhanced confinement phase in W7-X Open
Radial profiles of density fluctuations and the radial electric field, E r , have been measured using Doppler reflectometry during the post-pellet enhanced confinement phase achieved, under different heating power levels and magnetic confi…
View article: Investigation of TESPEL cloud dynamics in Wendelstein 7-X stellarator
Investigation of TESPEL cloud dynamics in Wendelstein 7-X stellarator Open
Tracer-encapsulated solid pellet (TESPEL) was injected from the outboard midplane into Wendelstein 7-X (W7-X) plasmas. Viewing from behind the flight path, the distribution of the light emissions from the TESPEL cloud particles (H, C and C…
View article: Characterization of the radial electric field and edge velocity shear in Wendelstein 7-X
Characterization of the radial electric field and edge velocity shear in Wendelstein 7-X Open
In this work we present the first measurements obtained by the V-band Doppler reflectometer during the second operation phase of Wendelstein 7-X to discuss the influence in the velocity shear layer and the radial electric field, E$_r$, of …
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: Validation of the BEAMS3D neutral beam deposition model on Wendelstein 7-X
Validation of the BEAMS3D neutral beam deposition model on Wendelstein 7-X Open
The neutral beam deposition model in the BEAMS3D code is validated against neutral beam attenuation data from Wendelstein 7-X (W7-X). A set of experimental discharges where the neutral beam injection system of W7-X was utilized were recons…
View article: Enhanced energy confinement after series of pellets in Wendelstein 7-X
Enhanced energy confinement after series of pellets in Wendelstein 7-X Open
A series of ice pellets was injected into the advanced stellarator Wendelstein 7-X (W7-X). Although the pellets were small and slow, deep and efficient particle fueling could be observed experimentally. The most striking feature appearing …
View article: High-performance plasmas after pellet injections in Wendelstein 7-X
High-performance plasmas after pellet injections in Wendelstein 7-X Open
A significant improvement of plasma parameters in the optimized stellarator W7-X is found after injections of frozen hydrogen pellets. The ion temperature in the post-pellet phase exceeds 3 keV with 5 MW of electron heating and the global …
View article: Soft x-ray tomography measurements in the Wendelstein 7-X stellarator
Soft x-ray tomography measurements in the Wendelstein 7-X stellarator Open
The soft x-ray tomography diagnostic in the stellarator Wendelstein 7-X consists of twenty pinhole cameras, up–down symmetrically arranged in a poloidal, triangular cross-section of the plasma vessel. The x-ray emissivity is measured with …
View article: Increasing the density in Wendelstein 7-X: benefits and limitations
Increasing the density in Wendelstein 7-X: benefits and limitations Open
In stellarators, increasing the density is beneficial for the energy confinement. While there is no single reason for this observation, it is still very robust across different devices and this is reflected in the empirical energy confinem…
View article: Performance of Wendelstein 7-X stellarator plasmas during the first divertor operation phase
Performance of Wendelstein 7-X stellarator plasmas during the first divertor operation phase Open
Wendelstein 7-X is the first comprehensively optimized stellarator aiming at good confinement with plasma parameters relevant to a future stellarator power plant. Plasma operation started in 2015 using a limiter configuration. After instal…
View article: Pellet fueling experiments in Wendelstein 7-X
Pellet fueling experiments in Wendelstein 7-X Open
During the two most recent experimental campaigns in the advanced stellarator Wendelstein 7-X (W7-X) (Klinger et al 2017 Plasma Phys. Control. Fusion 59 014018; Bosch et al 2017 Nucl. Fusion 57 116015; Wolf et al 2017 Nucl. Fusion 57 10202…
View article: Bayesian modeling of microwave radiometer calibration on the example of the Wendelstein 7-X electron cyclotron emission diagnostic
Bayesian modeling of microwave radiometer calibration on the example of the Wendelstein 7-X electron cyclotron emission diagnostic Open
This paper reports about a novel approach to the absolute intensity calibration of an electron cyclotron emission (ECE) spectroscopy system. Typically, an ECE radiometer consists of tens of separated frequency channels corresponding to dif…
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: Electron-cyclotron-resonance heating in Wendelstein 7-X: A versatile heating and current-drive method and a tool for in-depth physics studies
Electron-cyclotron-resonance heating in Wendelstein 7-X: A versatile heating and current-drive method and a tool for in-depth physics studies Open
For stellarators, which need no or only small amounts of current drive, electron-cyclotron-resonance heating (ECRH) is a promising heating method even for the envisaged application in a fusion power plant. Wendelstein 7-X (W7-X) is equippe…
View article: Phased array Doppler reflectometry at Wendelstein 7-X
Phased array Doppler reflectometry at Wendelstein 7-X Open
A passive phased array Doppler reflectometry system has recently been installed in the Wendelstein-7X stellarator. In contrast to conventional Doppler reflectometry systems, the microwave beam can be steered on short time scales in the mea…