Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 16
Book Description
Effects of Radial Electric Fields on the Turbulence and Transport in the TEXTOR Edge and SOL Plasma
Author: The Dynamics of Electrons in Linear Plasma Devices and Its Impact on Plasma Surface Interaction
Author: Michael HubenyPublisher: Springer
ISBN: 303012536X
Category : Science
Languages : en
Pages : 137
Book Description
Turbulence in plasma surface interaction holds crucial uncertainties for its impact on material erosion in the operation of fusion reactors. In this thesis, the design, development and operation of a Thomson scattering diagnostic and its novel implementation with fast visual imaging created a versatile tool to investigate intermittently occuring plasma oscillations. Specifically, ballistic transport events in the plasma edge, constituting turbulent transport, have been targeted in this thesis. With the help of a custom photon counting algorithm, the conditional averaging technique was applied on Thomson scattering for the first time to allow spatial and pseudo-time-resolved measurements. Since plasma turbulence and the emerging transport phenomena are comparable in most magnetized devices, the diagnostic development and the results from the linear plasma device PSI-2 are useful for an implementation of similar techniques in larger fusion experiments. Furthermore, the obtained results indicate a strong enhancement of erosion with turbulent transport and thus underline the importance of dedicated experiments investigating plasma turbulence in the framework of erosion in future fusion reactors.
Euro Abstracts
Author: Current Trends in International Fusion Research
Author: Charles D. OrthPublisher: NRC Research Press
ISBN: 9780660197074
Category : Science
Languages : en
Pages : 558
Book Description
Physics Briefs
Author: Euroabstracts
Author: The Influence of the Dynamic Ergodic Divertor on the Radial Electric Field at the Tokamak TEXTOR
Author: Jan Willem CoenenPublisher: Forschungszentrum Jülich
ISBN: 3893365745
Category :
Languages : en
Pages : 171
Book Description
Scientific and Technical Aerospace Reports
Author: Turbulent Transport of Energetic Ions and Thermal Plasmas
Author: Shu ZhouPublisher:
ISBN: 9781267075536
Category :
Languages : en
Pages : 176
Book Description
Three experiments are conducted to study the effect of the turbulent waves on the transport of fast ions and thermal plasmas. In the first experiment, strong drift wave turbulence with linear geometry is observed in the Large Plasma Device (LAPD) on density gradients produced by a plate limiter. Energetic lithium ions orbit through the turbulent region. Scans with a collimated ion analyzer and with Langmuir probes give detailed profiles of the fast ion spatial distribution and the fluctuating fields. The fast-ion transport decreases rapidly with increasing fast-ion gyroradius. Unlike the diffusive transport caused by Coulomb collisions, in this case the turbulent transport is super-diffusive. Analysis and simulation suggest that such super-diffusive transport is due to the interaction of the fast ions with the low-frequency two-dimensional electrostatic turbulence. The second experiment studies the dependence of the fast ion transport on the nature of the turbulent waves. Strong turbulent waves with cylindrical geometry are observed in the LAPD on density gradients produced by an annular obstacle. The characteristics of the fluctuations are modified by changing the plasma species from helium to neon, and by modifying the bias on the obstacle. Different spatial structure sizes and correlation lengths (Lcorr) of the wave potential fields alter the fast ion transport. The effects of electrostatic fluctuations are reduced due to gyro-averaging, which explains the difference in the fast-ion transport. A transition from super-diffusive to sub-diffusive transport is observed when the fast ion interacts with the waves for most of a wave period, which agrees with theoretical predictions. The transport of thermal plasmas under electrostatic waves is explored in the third experiment. Sheared azimuthal flow is driven at the edge of a magnetized plasma cylinder through edge biasing. Strong fluctuations of density and potential are observed at the plasma edge, accompanied by large density gradient. Edge turbulence and cross-field transport are modified by changing the bias voltage on the obstacle and the axial magnetic field strength. In cases with low V bias and large Bz, improved plasma confinement is observed, along with steeper edge density gradients. The radially sheared flow induced by E x B dramatically changes the cross-phase between density and potential fluctuations, which causes the wave-induced particle flux to reverse its direction across the shear layer and forms a transport barrier. In cases with higher bias voltage or smaller Bz large radial transport and rapid depletion of the central plasma density are observed. Two-dimensional cross-correlation measurement shows that a mode with azimuthal mode number m=1 and large radial correlation length dominates the outward transport in these cases. Linear analysis based on a two-fluid Braginskii model suggests that the fluctuations are driven by both density gradient and flow shear at the plasma edge.
Author: