Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
This paper describes 2-D imaging measurements of plasma turbulence made in the scrape-off layer of the Alcator C-Mod tokamak simultaneously at two different poloidal locations, one near the outer midplane and the other near the divertor X-point region. These images were made with radial and poloidal resolution using two gas puff imaging (GPI) diagnostics, which were not directly connected along a B field line. The turbulence correlation structure has a significantly different tilt angle with respect to the local flux surfaces for the midplane and X-regions, and a slightly different ellipticity and size. The time-averaged turbulence velocities can be different in the midplane and Xregions, even within the same flux surface in the same shot, and in most cases the fluctuations in poloidal velocity in these two regions were not correlated. These structures are partially consistent with a magnetic flux tube mapping model, and the velocities are compared with various poloidal flow models.
Comparison of Edge Turbulence Imaging at Two Different Poloidal Locations in the Scrape-off Layer of Alcator C-Mod
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
This paper describes 2-D imaging measurements of plasma turbulence made in the scrape-off layer of the Alcator C-Mod tokamak simultaneously at two different poloidal locations, one near the outer midplane and the other near the divertor X-point region. These images were made with radial and poloidal resolution using two gas puff imaging (GPI) diagnostics, which were not directly connected along a B field line. The turbulence correlation structure has a significantly different tilt angle with respect to the local flux surfaces for the midplane and X-regions, and a slightly different ellipticity and size. The time-averaged turbulence velocities can be different in the midplane and Xregions, even within the same flux surface in the same shot, and in most cases the fluctuations in poloidal velocity in these two regions were not correlated. These structures are partially consistent with a magnetic flux tube mapping model, and the velocities are compared with various poloidal flow models.
Publisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
This paper describes 2-D imaging measurements of plasma turbulence made in the scrape-off layer of the Alcator C-Mod tokamak simultaneously at two different poloidal locations, one near the outer midplane and the other near the divertor X-point region. These images were made with radial and poloidal resolution using two gas puff imaging (GPI) diagnostics, which were not directly connected along a B field line. The turbulence correlation structure has a significantly different tilt angle with respect to the local flux surfaces for the midplane and X-regions, and a slightly different ellipticity and size. The time-averaged turbulence velocities can be different in the midplane and Xregions, even within the same flux surface in the same shot, and in most cases the fluctuations in poloidal velocity in these two regions were not correlated. These structures are partially consistent with a magnetic flux tube mapping model, and the velocities are compared with various poloidal flow models.
Observations of the Turbulence in the Scrape-off-layers of Alcator C-Mod and NSTX and Comparisons with Simualtion [sic]
Author: James L. Terry
Publisher:
ISBN:
Category :
Languages : en
Pages : 44
Book Description
The intermittent turbulent transport in the scrape-off-layer of Alcator C-Mod and NSTX is studied experimentally by imaging with a very high density of spatial measurements. The 2-D structure and dynamics of emission from a localized gas puff are observed, and intermittent features (also sometimes called "filaments" or "blobs") are typically seen. The characteristics of the spatial structure of the turbulence and their relationship to the time-averaged SOL profiles are discussed. The experimental observations are compared with 3-D non-linear numerical simulations of edge turbulence. Radial profiles of the poloidal wavenumber spectra and the poloidal scale length from the simulations are in reasonable agreement with those obtained from the experimental images, once the response of the optical system is accounted for. The resistive ballooning mode is the dominant linear instability in the simulations. The ballooning character of the turbulence is also consistent with fluctuation measurements made at the inboard and outboard midplane, where normalized fluctuation levels are found to be about ten times smaller on the inboard side. For discharges near the density limit, turbulent structures are seen on closed flux surfaces. Keywords: turbulence; edge plasma; fluctuations; transport phenomena; resistive instabilities.
Publisher:
ISBN:
Category :
Languages : en
Pages : 44
Book Description
The intermittent turbulent transport in the scrape-off-layer of Alcator C-Mod and NSTX is studied experimentally by imaging with a very high density of spatial measurements. The 2-D structure and dynamics of emission from a localized gas puff are observed, and intermittent features (also sometimes called "filaments" or "blobs") are typically seen. The characteristics of the spatial structure of the turbulence and their relationship to the time-averaged SOL profiles are discussed. The experimental observations are compared with 3-D non-linear numerical simulations of edge turbulence. Radial profiles of the poloidal wavenumber spectra and the poloidal scale length from the simulations are in reasonable agreement with those obtained from the experimental images, once the response of the optical system is accounted for. The resistive ballooning mode is the dominant linear instability in the simulations. The ballooning character of the turbulence is also consistent with fluctuation measurements made at the inboard and outboard midplane, where normalized fluctuation levels are found to be about ten times smaller on the inboard side. For discharges near the density limit, turbulent structures are seen on closed flux surfaces. Keywords: turbulence; edge plasma; fluctuations; transport phenomena; resistive instabilities.
Edge Turbulence Imaging in the Alcator C-Mod Tokamak
Edge Turbulence Imaging on NSTX and Alcator C-mod
Author: S. J. Zweben
Publisher:
ISBN:
Category : National Spherical Torus Experiment (Project)
Languages : en
Pages : 4
Book Description
Publisher:
ISBN:
Category : National Spherical Torus Experiment (Project)
Languages : en
Pages : 4
Book Description
Turbulence and Transport Phenomena in Edge and Scrape-off-layer Plasmas
Author: István Cziegler
Publisher:
ISBN:
Category :
Languages : en
Pages : 178
Book Description
This thesis reports recent experimental studies of edge turbulence structure using gas-puff-imaging at high time resolution in a radially broad zone at the low-field-side of Alcator C-Mod[1], and highlights the connections between its characteristics and particle transport. Within the framework of this thesis a new detector system has been designed and built for viewing the steep gradient outboard midplane region at minor radii 0.9
Publisher:
ISBN:
Category :
Languages : en
Pages : 178
Book Description
This thesis reports recent experimental studies of edge turbulence structure using gas-puff-imaging at high time resolution in a radially broad zone at the low-field-side of Alcator C-Mod[1], and highlights the connections between its characteristics and particle transport. Within the framework of this thesis a new detector system has been designed and built for viewing the steep gradient outboard midplane region at minor radii 0.9
Scientific and Technical Aerospace Reports
Annual Highlights
Author: Princeton University. Plasma Physics Laboratory
Publisher:
ISBN:
Category : Controlled fusion
Languages : en
Pages : 182
Book Description
Publisher:
ISBN:
Category : Controlled fusion
Languages : en
Pages : 182
Book Description
The Dynamics of Electrons in Linear Plasma Devices and Its Impact on Plasma Surface Interaction
Author: Michael Hubeny
Publisher: 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.
Publisher: 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.
Physics Briefs
Applied Computational Geometry. Towards Geometric Engineering
Author: Ming C. Lin
Publisher: Springer Science & Business Media
ISBN: 9783540617853
Category : Computers
Languages : en
Pages : 244
Book Description
Content Description #Anthology selected from contributions to the First ACM Workshop on Applied Computational Geometry.#Includes bibliographical references and index.
Publisher: Springer Science & Business Media
ISBN: 9783540617853
Category : Computers
Languages : en
Pages : 244
Book Description
Content Description #Anthology selected from contributions to the First ACM Workshop on Applied Computational Geometry.#Includes bibliographical references and index.