Ion-Bernstein-Wave Heating and Improved Confinement in the Alcator C Tokamak

Plasma heating by directly launched ion Bernstein waves is investigated in the Alcator C tokamak at densities n̄ₑ1×10²⁰ m^-3. For injected rf powers Prf180 kW, bulk-ion-temperature increases of ΔTᵢ380 eV, as well as improvements in global particle and central impurity confinement times by a factor of 2-3, are observed. In certain regimes, the energy-confinement time improves relative to the initial Ohmic value. At higher densities (n̄ₑ2×10²⁰ m^-3), the heating ceases to be efficient.