Study of Alfv\'{e}n Eigenmodes on the Madison Symmetric Torus

Alfv\'{e}n waves are likely of fundamental importance in the reversed-field pinch (RFP). Unstable tearing fluctuations can inject energy into Alfv\'{e}n modes, which could excite broadband magnetic turbulence and anomalous ion heating. An effort is in progress to understand toroidicity-induced Alfv\'{e}n eigenmodes (TAE's) through their structure, driving terms and damping mechanisms on the MST. Coupling of multiple continuum modes can introduce undamped Alfv\'{e}n eigenmodes with frequencies up to 1 MHz. These modes can also become unstable by inverse Landau damping due to fast ions, a condition pertinent to neutral beam injection heating on MST and fusion alpha particles in future RFP devices. Frequencies of weakly damped modes have been calculated by solving a 3D partial differential equation that describes shear Alfv\'{e}n dynamics numerically based on MST equilibrium conditions. To excite the calculated modes, a single strap poloidal antenna connected to a 1 kW broadband amplifier will be employed. A toroidal array of 32 fast magnetic loops resolves power spectra and mode numbers in the relevant range of frequencies. Preliminary data indicates some coherent magnetic activity below TAE frequency ranges. Supported by USDoE and NSF.