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Title: Self-organized T e Redistribution during Driven Reconnection Processes in High Temperature Plasmas

Abstract

Two-dimensional (2-D) images of electron temperature fluctuations with a high temporal and spatial resolution were employed to study the sawtooth oscillation in TEXTOR tokamak plasmas. The new findings are: (1) 2-D images revealed that the reconnection is localized and permitted the determination of the physical dimensions of the reconnection zone in the poloidal and toroidal planes. (2) The combination of a pressure driven mode and a kink instability leads to an "X-point" reconnection process. (3) Reconnection can take place anywhere along the q~1 rational magnetic surface (both high and low field sides). (4) Heat flow from the core to the outside of the inversion radius during the reconnection time is highly asymmetric and the behavior is collective. These new findings are compared with the characteristics of various theoretical models and experimental results for the study of the sawtooth oscillation in tokamak plasmas.

Authors:
; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
934602
Report Number(s):
PPPL-4134
TRN: US0804645
DOE Contract Number:
AC02-76CH03073
Resource Type:
Technical Report
Resource Relation:
Related Information: Published in: Phys. Plasmas 13, 055907 (2006)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; DIMENSIONS; ELECTRON TEMPERATURE; FLUCTUATIONS; HEAT FLUX; KINK INSTABILITY; MAGNETIC SURFACES; SAWTOOTH OSCILLATIONS; SPATIAL RESOLUTION; TEXTOR TOKAMAK; plasma temperature, plasma fluctuations, plasma magnetohydrodynamics, sawtooth instability, plasma oscillations, Tokamak devices, plasma toroidal confinement, plasma pressure, kink instability, plasma transport processes

Citation Formats

Park, H. K., Mazzucato, E., Luhmann, Jr., N. C., Domier, C. W., Xia, Z., Munsat, T., Donne, A. J.H., Classen, I. G.J., and van de Pol, M. J.. Self-organized Te Redistribution during Driven Reconnection Processes in High Temperature Plasmas. United States: N. p., 2005. Web. doi:10.2172/934602.
Park, H. K., Mazzucato, E., Luhmann, Jr., N. C., Domier, C. W., Xia, Z., Munsat, T., Donne, A. J.H., Classen, I. G.J., & van de Pol, M. J.. Self-organized Te Redistribution during Driven Reconnection Processes in High Temperature Plasmas. United States. doi:10.2172/934602.
Park, H. K., Mazzucato, E., Luhmann, Jr., N. C., Domier, C. W., Xia, Z., Munsat, T., Donne, A. J.H., Classen, I. G.J., and van de Pol, M. J.. Thu . "Self-organized Te Redistribution during Driven Reconnection Processes in High Temperature Plasmas". United States. doi:10.2172/934602. https://www.osti.gov/servlets/purl/934602.
@article{osti_934602,
title = {Self-organized Te Redistribution during Driven Reconnection Processes in High Temperature Plasmas},
author = {Park, H. K. and Mazzucato, E. and Luhmann, Jr., N. C. and Domier, C. W. and Xia, Z. and Munsat, T. and Donne, A. J.H. and Classen, I. G.J. and van de Pol, M. J.},
abstractNote = {Two-dimensional (2-D) images of electron temperature fluctuations with a high temporal and spatial resolution were employed to study the sawtooth oscillation in TEXTOR tokamak plasmas. The new findings are: (1) 2-D images revealed that the reconnection is localized and permitted the determination of the physical dimensions of the reconnection zone in the poloidal and toroidal planes. (2) The combination of a pressure driven mode and a kink instability leads to an "X-point" reconnection process. (3) Reconnection can take place anywhere along the q~1 rational magnetic surface (both high and low field sides). (4) Heat flow from the core to the outside of the inversion radius during the reconnection time is highly asymmetric and the behavior is collective. These new findings are compared with the characteristics of various theoretical models and experimental results for the study of the sawtooth oscillation in tokamak plasmas.},
doi = {10.2172/934602},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Thu Dec 01 00:00:00 EST 2005},
month = {Thu Dec 01 00:00:00 EST 2005}
}

Technical Report:

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  • Two-dimensional (2D) images of electron temperature fluctuations with high temporal and spatial resolution were employed to study the sawtooth oscillation in Toroidal EXperiment for Technology Oriented Research [S. S. Abdallaev et al., Nucl. Fusion 43, 299 (2003)] tokamak plasmas. The new findings are: (1) 2D images revealed that the reconnection is localized and permitted the determination of the physical dimensions of the reconnection zone in the poloidal and toroidal planes. (2) The combination of a pressure bulge due to finite pressure effects or a kink instability accompanied with a sharp pressure point leads to an 'X-point' reconnection process. (3) Reconnectionmore » can take place anywhere along the q{approx}1 rational magnetic surface (both high- and low-field sides). (4) Heat flow from the core to the outside of the inversion radius during the reconnection time is through the finite opening on the poloidal and toroidal planes and the flow is highly collective. These new findings are compared with the characteristics of various theoretical models and experimental results for the study of the sawtooth oscillation in tokamak plasmas.« less
  • High resolution (temporal and spatial), two-dimensional images of electron temperature fluctuations during sawtooth oscillations were employed to study driven reconnection processes in magnetically confined toroidal plasmas. The combination of kink and local pressure driven instabilities leads to an "X-point" reconnection process that is localized in the toroidal and poloidal planes. The reconnection is not always confined to the magnetic surfaces with minimum energy. The heat transport process from the core is demonstrated to be highly collective rather than stochastic.
  • It is clear that the edge plasma plays a crucial role in global tokamak confinement. This paper is a report on simulations of a new drift wave type instability driven by the electron temperature gradient in tokamak scrapeoff-layers (SOL). A 2d fluid code has been developed in order to explore the anomalous transport in the boundary plasmas. The simulation consists of a set of fluid equations for the vorticity {nabla}{sub {perpendicular}}{sup 2}{phi}, the electron density n{sub c} and the temperature T{sub c} in a shearless plasma slab confined by a uniform, straight magnetic field B{sub z} with two divertor (ormore » limiter) plates intercepting the magnetic field. The model has two regions separated by a magnetic separatrix: in the edge region inside the separatrix, the model is periodic along the magnetic field while in the SOL region outside the separatrix, the magnetic field is taken to be of finite length with model boundary conditions at diverter plates. The simulation results show that the observed linear instability agrees well with theory, and that a saturated state of turbulence is reached. In saturated turbulence, clear evidence of the expected long-wavelength mode penetration into the edge is seen, an inverse cascade of wave energy is observed. The simulation results also show that amplitudes of potential and the electron temperature fluctuations are somewhat above and the heat flux are somewhat below those of the simplest mixing-length estimates, and furthermore the large-scale radial structures of fluctuation quantities indicate that the cross-field transport is not diffusive. After saturation, the electron density and temperature profiles are flattened. A self-consistent simulation to determine the microturbulent SOL electron temperature profile has been done, the results of which reasonably agree with the experimental measurements.« less
  • Toroidal effects on the ion-temperature gradient mode are found to dictate the temperature evolution and the subsequent relaxed profile realization according to our toroidal particle simulation. Both in the strongly unstable fluid regime as well as in the near-marginal kinetic regime we observe that the plasma maintains an exponential temperature profile and forces the heat flux to be radially independent. The self-organized critical relaxed state is sustained slightly above the marginal stability, where the weak wave growth balances the wave decorrelation.
  • Toroidal effects on the ion-temperature gradient mode are found to dictate the temperature evolution and the subsequent relaxed profile realization according to our toroidal particle simulation. Both in the strongly unstable fluid regime as well as in the near-marginal kinetic regime we observe that the plasma maintains an exponential temperature profile and forces the heat flux to be radially independent. The self-organized critical relaxed state is sustained slightly above the marginal stability, where the weak wave growth balances the wave decorrelation.