The experiment will be conducted in the current-ramp phase of a low density ∼ 2e19m^{-3} L-mode plasma, a condition that reliably produces TAEs and high quality INPA data. One beam (the so-called “active” beam) injects neutrals at a reduced voltage of ∼ 55 keV that charge exchange with the fast ions to produce INPA and fast-ion D-alpha (FIDA) signals, while another beam at full voltage (81 keV) produces the fast ion population that drives TAE instability and is diagnosed. The high energy beam is modulated in order to vary the TAE activity and to infer phase-space flows. Injection of high-energy beams with different injection geometry populates different portions of phase space. The fast ions are diagnosed both by the INPA that is sensitive to ions on “passing” orbits with relatively large parallel velocities and by a new INPA that is sensitive to ions on “trapped” orbits with small parallel velocity, as well as a new imaging FIDA diagnostic and neutron measurements. The TAEs are diagnosed by an ECE radiometer and an ECE imaging diagnostic. Ideally, we would directly measure the local electric field produced by the wave but this is not a measured quantity in DIII-D. However, fluctuations in electron temperature are accurately measured, the equilibrium field is well diagnosed using motional Stark effect based equilibrium reconstructions, and the TAE eigenfunction is well measured and modeled, so time-resolved values of the wave field can be accurately inferred from the data. Measurements of the internal magnetic field by the radial interferometer-polarimeter will corroborate the inferred electric field. The required discharge conditions and diagnostics for this experiment are already available. In experiment, calculate the energy transfer between fast ions and waves in different parts of phase space from the correlation of the changes in F inferred from the fast-ion diagnostics and the electric field inferred from electron temperature fluctuation. We will also simulate the experimental condition with MEGA. Local phase-space fluctuations in the distribution function will be inferred from the particle markers, the electric field from the calculated potentials, and the correlation between these quantities calculated for comparison with experiment.