Fusion alpha-particle losses in a high-beta rippled tokamak
- Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)
- National Institute for Fusion Science, Toki 509-5292 (Japan)
- Japan Atomic Energy Agency, Naka, Ibaraki 311-0193 (Japan)
- Nippon Advanced Technology, Naka, Ibaraki 311-0102 (Japan)
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 field 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.
- OSTI ID:
- 22227913
- Journal Information:
- Physics of Plasmas, Vol. 20, Issue 8; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
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