PFC / JA - 90 - 27 A Stability Criterion for Energetic Particle - Alfv 6 n Modes
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Theoretical Interpretation of Alfv en Cascades in Tokamaks with Non-monotonic q-pro les
Alfv en spectra in a reversed-shear tokamak plasma with a population of energetic ions exhibit a quasiperiodic pattern of primarily upward frequency sweeping (Alfv en Cascade). Presented here is an explanation for such asymmetric sweeping behavior which involves nding a new energetic particle mode localized around the point of zero magnetic shear.
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A numerical investigation of ideal magnetohydrodynamic stability in finite aspect ratio tokamaks with zero edge current density is carried out. It is shown that, assuming a conventionally D-shaped cross section and a safety factor on axis greater than 2.1, both n = oo and n = 1 modes are stable for any beta, even in the absence of any surrounding conductors.
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Localized alpha-particle velocity distribution and density, ion temperature, DT fuel ratio, and internal magnetic field pitch angle can all be potentially diagnosed by a collective Thomson scattering system. Relativistic electron cyclotron calculations and TORAY ray tracing for 6 tesla ITER parameters indicate that 90 GHz is an optimum frequency for this diagnostic. With 400 kW at the plasma an...
متن کاملOT 7 Particle Simulations of Alfvén Modes in Reversed-Shear DIII-D Discharges Heated by Neutral Beams∗
A rich spectrum of oscillations in the Alfvénic range has been observed in DIII-D tokamak reversedshear discharges heated by neutral beams. During the discharge phase characterized by Alfvénic activity, the energetic particle density profile, as calculated by a classical deposition model (TRANSP), appears to be much more peaked than that observed experimentally, as inferred, e.g., from the equi...
متن کاملEnergetic Particle Mode Dynamics in Tokamaks
Energetic Particle Modes [1] (EPM) are strongly driven oscillations excited via wave-particle resonant interactions at the characteristic frequencies of the energetic ions [1, 2], ωtE, ωBE and/or ωdE , i.e., respectively the transit frequency for circulating particles and the bounce and precessional drift frequencies for trapped ions. A sharp transition in the plasma stability at the critical E...
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