The paper presents the results of an experimental study of the wave fields excited in a tokamak plasma under Alfvén wave heating conditions, with a large number of Alfvén resonance surfaces present in the plasma. The wave fields excited by Faraday shielded antennas with current elements oriented in the poloidal direction were measured by an array of magnetic probes positioned along a vertical diameter of the plasma. Pronounced enhancement of the wave fields at the radii of Alfvén resonance surfaces was observed. The dependence of the wave field profiles on the plasma parameters and on the toroidal and poloidal positions is analysed with the help of a simple theoretical model. Evidence of the excitation of the outward propagating surface electrostatic wave is presented. The profiles excited by a number of phasings of an array of three toroidally spaced antennas are compared. The results provide unambiguous evidence that the peaks in the profiles are due to mode conversion of the compressional Alfvén wave to the torsional Alfvén wave at Alfvén resonance surfaces. Measurements of the resistive loading of the antenna indicate that up to 50% of the total wave power was deposited at Alfvén resonance surfaces well inside the plasma and 40% at a single Alfvén resonance surface.
Far-forward scattering observations of an Alfven wave experiment