Transport of Fast Ions Modulated by Shear Alfv\'{e}n Waves*

The interaction of fast particles with Alfv\'{e}n instabilities is important in magnetic fusion devices and natural plasmas. In this experiment, shear Alfv\'{e}n waves (SAW) modulate fast ion transport through Doppler shifted cyclotron resonance, in addition to the classical collisional diffusion. A Li$^{+}$ ion source is inserted in the LArge Plasma Device (LAPD) with ion energy up to $\sim $2000 eV, detected by a collimated fast ion energy analyzer. RF antennas launch waves with amplitude of $\backslash $delta B/B $\sim $ 0.1{\%} that propagate along the machine axis. When launched in (out of) phase with the perpendicular wave electric field, fast ions gain (lose) energy from (to) the wave. A $\sim $10{\%} increase in the beam radial width and beam signal modulation at SAW frequency are observed. These fast ion transport phenomena peak near the predicted resonance condition. ($\omega _{Alfv\mbox{\'{e}}n}$ -- k$_{z}$v$_{z}=\omega _{fast-ion})$