55 research outputs found
Application of the elliptic approximation model for the edge turbulence rotation measurement via the poloidal correlation reflectometer in Wendelstein 7-X
ECCD-induced sawtooth crashes at W7-X
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 current drive experiments were conducted for strikeline control and safe divertor
operation. During current drive experiments periodic and repetitive crashes of the central
electron temperature, similar to sawtooth crashes in tokamaks, were detected. Measurements
from soft x-ray tomography and electron cyclotron emission show that the crashes are preceded
by weak oscillating precursors and a displacement of the plasma core, consistent with a
(m, n)=(1, 1) mode. The displacement occurs within 100μs, followed by expulsion and
redistribution of the core into the external part of the plasma. Two types of crashes, with
different frequencies and amplitudes are detected in the experimental program. For these
non-stationary parameters a strong dependence on the toroidal current is found. A 1-D heuristic
model for current diffusion is proposed as a first step to explain the characteristic crash time.
Initial results show that the modelled current diffusion timescale is consistent with the initial
crash frequency and that the toroidal current rise shifts the position where the instability is
triggered, resulting in larger crash amplitudes
Benchmark datasets for 3D MALDI- and DESI-imaging mass spectrometry
BACKGROUND: Three-dimensional (3D) imaging mass spectrometry (MS) is an analytical chemistry technique for the 3D molecular analysis of a tissue specimen, entire organ, or microbial colonies on an agar plate. 3D-imaging MS has unique advantages over existing 3D imaging techniques, offers novel perspectives for understanding the spatial organization of biological processes, and has growing potential to be introduced into routine use in both biology and medicine. Owing to the sheer quantity of data generated, the visualization, analysis, and interpretation of 3D imaging MS data remain a significant challenge. Bioinformatics research in this field is hampered by the lack of publicly available benchmark datasets needed to evaluate and compare algorithms. FINDINGS: High-quality 3D imaging MS datasets from different biological systems at several labs were acquired, supplied with overview images and scripts demonstrating how to read them, and deposited into MetaboLights, an open repository for metabolomics data. 3D imaging MS data were collected from five samples using two types of 3D imaging MS. 3D matrix-assisted laser desorption/ionization imaging (MALDI) MS data were collected from murine pancreas, murine kidney, human oral squamous cell carcinoma, and interacting microbial colonies cultured in Petri dishes. 3D desorption electrospray ionization (DESI) imaging MS data were collected from a human colorectal adenocarcinoma. CONCLUSIONS: With the aim to stimulate computational research in the field of computational 3D imaging MS, selected high-quality 3D imaging MS datasets are provided that could be used by algorithm developers as benchmark datasets
EMC3-EIRENE simulation of first wall recycling fluxes in W7-X with relation to H-alpha measurements
In the Wendelstein 7-X stellarator, the main locations of particle sources are expected to be the carbon divertors, baffles and graphite heat shield first wall. In this paper, the heat shield is implemented in EMC3-EIRENE to understand the expected areas and magnitudes of the recycling flux to this component. It is found that in the simulation the heat shield is not a significant source of recycling neutrals. The areas of simulated recycling flux are shown to correlate well with footprints of plasma-wetting seen in post-experimental campaign in-vessel inspection photos. EMC3-EIRENE reconstruction of line-integrated H-alpha measurements at the heat shield indicate that the majority of emission does not come from local recycling neutrals. Rather, the H-alpha signals at the heat shield are dominated by ionization of neutrals which have leaked from the divertor/baffle region into the midplane. The magnitude of the H-alpha line emission from the synthetic reconstruction is consistent with the experiment, indicating that a large overestimation of heat shield recycling would occur if these measurements were assumed to be from local recycling sources. In the future, it may be possible to obtain some information of local recycling from the heat shield since it was found that the majority of the recycling flux occurs on two well-localized areas
Nuclear Fusion (FUSION): Plasma Heating Systems -Microwave Plasma Heating & Current Drive System
Nuclear Fusion (FUSION): Plasma Heating Systems – Microwave Plasma Heating & Current Drive Systems
Brazilian mothers' description of their children: dimensions of autonomy and relatedness
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