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Title: Spherical tokamak with a plasma center column

Abstract

Low aspect ratio toroidal pinches such as the standard (q>1) and the ultralow q (q<1) spherical tori or tokamaks (ST), would have a far more robust reactor engineering design if a plasma center column (PCC) can be used in place of a material center post. Biased electrodes across the plasma center column would drive a plasma current to produce the toroidal magnetic field in lieu of the toroidal field (TF) coils. The operation of such a device is naturally divided into two distinct phases: formation by driven relaxation under magnetic helicity injection and sustainment by auxiliary current drive and heating such as rf and neutral beam injection (NBI). The initial design constraints of a ST-PCC experiment are primarily motivated by the formation rather than the sustainment physics. With a Taylor-relaxed plasma as the baseline case, it is shown that three essential factors guide the design. First, the flux amplification factor determines the aspect ratio of the ST-PCC. Second, the plasma shaping in general and plasma elongation in particular gives the most freedom in shaping the q profile of the relaxed plasma. Two examples are the standard spherical tokamak with q>1 throughout the plasma and the ultralow q (ULQ) spherical tokamakmore » with q much less than unity for the bulk of the plasma. Third, the vacuum bias magnetic flux plays the second most important role in modifying the q profile. As an example, it is shown how the bias flux can be designed to delineate a standard spheromak experiment from that of an ULQ ST-PCC. These physics understandings help define the design space of the ST-PCC experiments and directions for optimization.« less

Authors:
;  [1];  [2]
  1. Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
20782750
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 13; Journal Issue: 4; Other Information: DOI: 10.1063/1.2195381; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ASPECT RATIO; BEAM INJECTION HEATING; DESIGN; ELECTRIC CURRENTS; ELONGATION; HELICITY; MAGNETIC FIELDS; MAGNETIC FLUX; OPTIMIZATION; PINCH EFFECT; PLASMA; PLASMA BEAM INJECTION; PLASMA CONFINEMENT; RADIATION TRANSPORT; RELAXATION; RF SYSTEMS; SPHEROMAK DEVICES; THERMONUCLEAR REACTORS

Citation Formats

Tang, X.Z., Boozer, A.H., and Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027. Spherical tokamak with a plasma center column. United States: N. p., 2006. Web. doi:10.1063/1.2195381.
Tang, X.Z., Boozer, A.H., & Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027. Spherical tokamak with a plasma center column. United States. doi:10.1063/1.2195381.
Tang, X.Z., Boozer, A.H., and Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027. Sat . "Spherical tokamak with a plasma center column". United States. doi:10.1063/1.2195381.
@article{osti_20782750,
title = {Spherical tokamak with a plasma center column},
author = {Tang, X.Z. and Boozer, A.H. and Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027},
abstractNote = {Low aspect ratio toroidal pinches such as the standard (q>1) and the ultralow q (q<1) spherical tori or tokamaks (ST), would have a far more robust reactor engineering design if a plasma center column (PCC) can be used in place of a material center post. Biased electrodes across the plasma center column would drive a plasma current to produce the toroidal magnetic field in lieu of the toroidal field (TF) coils. The operation of such a device is naturally divided into two distinct phases: formation by driven relaxation under magnetic helicity injection and sustainment by auxiliary current drive and heating such as rf and neutral beam injection (NBI). The initial design constraints of a ST-PCC experiment are primarily motivated by the formation rather than the sustainment physics. With a Taylor-relaxed plasma as the baseline case, it is shown that three essential factors guide the design. First, the flux amplification factor determines the aspect ratio of the ST-PCC. Second, the plasma shaping in general and plasma elongation in particular gives the most freedom in shaping the q profile of the relaxed plasma. Two examples are the standard spherical tokamak with q>1 throughout the plasma and the ultralow q (ULQ) spherical tokamak with q much less than unity for the bulk of the plasma. Third, the vacuum bias magnetic flux plays the second most important role in modifying the q profile. As an example, it is shown how the bias flux can be designed to delineate a standard spheromak experiment from that of an ULQ ST-PCC. These physics understandings help define the design space of the ST-PCC experiments and directions for optimization.},
doi = {10.1063/1.2195381},
journal = {Physics of Plasmas},
number = 4,
volume = 13,
place = {United States},
year = {Sat Apr 15 00:00:00 EDT 2006},
month = {Sat Apr 15 00:00:00 EDT 2006}
}