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Title: Fusion alpha-particle losses in a high-beta rippled tokamak

In tokamak plasmas, the confinement of energetic ions depends on the magnetic field structure. If the plasma pressure is finite, the equilibrium current (i.e., the Pfirsch-Schlüter current and diamagnetic current) flows in the plasma to maintain the magnetohydrodynamic (MHD) equilibrium. These plasma currents generate poloidal and toroidal magnetic field and alter the field structure. Moreover, if we consider the non-axisymmetry of magnetic field structures such as toroidal field (TF) ripples, the non-axisymmetric component of the equilibrium current can alter TF ripples themselves. When the plasma beta becomes high, the changes in the field structure due to the equilibrium current might affect the confinement of energetic ions significantly. We intend to clarify how these currents alter the field structure and affect the confinement of alpha particles in high-beta plasma. The MHD equilibrium is calculated using VMEC and the orbits of fusion alpha particles are followed by using the fully three-dimensional magnetic field orbit-following Monte Carlo code. In relatively low-beta plasma (e.g., the volume-averaged beta value <β>≤2%), the changes in the magnetic field component due to the plasma current negligibly affect the confinement of alpha particles except for the Shafranov shift effect. However, for <β>≥3%, the diamagnetic effect reduces the magnetic fieldmore » strength and significantly increases alpha-particle losses. In these high-beta cases, the non-axisymmetric field component generated by the equilibrium current also increases these losses, but not as effectively as compared to the diamagnetic effect.« less
Authors:
;  [1] ;  [2] ; ;  [3] ;  [4]
  1. Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)
  2. National Institute for Fusion Science, Toki 509-5292 (Japan)
  3. Japan Atomic Energy Agency, Naka, Ibaraki 311-0193 (Japan)
  4. Nippon Advanced Technology, Naka, Ibaraki 311-0102 (Japan)
Publication Date:
OSTI Identifier:
22227913
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 20; Journal Issue: 8; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ALPHA PARTICLES; AXIAL SYMMETRY; COMPARATIVE EVALUATIONS; ELECTRIC CURRENTS; HIGH-BETA PLASMA; LOW-BETA PLASMA; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; MHD EQUILIBRIUM; MONTE CARLO METHOD; PLASMA CONFINEMENT; PLASMA DIAMAGNETISM; PLASMA PRESSURE; TAIL IONS; THREE-DIMENSIONAL CALCULATIONS; TOKAMAK DEVICES