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Cover of Physics of Plasmas July 2008

Cover image of PoP.

The next step toward fusion as a practical energy source is the design and construction of ITER [R. Aymar, V. A. Chuyanov, M. Huguet, Y. Shimomura, ITER Joint Central Team, ITER Home Teams, Nucl. Fusion 41, 1301 (2001)], a device capable of producing and controlling the high performance plasma required for self-sustaining fusion reactions, i.e. "burning plasma." ITER relies in part on ion-cyclotron radio frequency power to heat the deuterium and tritium fuel to fusion temperatures. In order to heat effectively, the radio frequency wave fields must couple efficiently to the dense core plasma. Calculations in this paper support the argument that this will be the case. Three dimensional full-wave simulations show that fast magnetosonic waves in ITER propagate radially inward with strong central focusing and little toroidal spreading. Energy deposition, current drive, and plasma flow are all highly localized near the plasma center. Very high resolution, two dimensional calculations reveal the presence of mode conversion layers, where fast waves can be converted to slow ion cyclotron waves. When minority ions such as deuterium or helium-3 are used to damp the launched waves, these ions can be accelerated to high energies, forming supra-thermal tails that significantly affect the wave propagation and absorption. By neglecting the toroidal localization of the waves and the finite radial excursion of the energetic particle orbits, the quasilinear evolution of these supra-thermal ion tails can be simulated self-consistently in one spatial dimension and two velocity dimensions.