Velocity space diffusion of ions in controlled turbulence

The velocity space diffusion of ions due to ion wave turbulence is investigated experimentally using an ion wave echo. Experiments are so arranged that the streaming perturbation due to the first excited wave propagates through the localized region where the ion wave turbulence is excited, to interact with the second excited wave. The resultant second order ion wave echo damps in comparison with the case of no turbulence. The variation of the echo amplitude as the power of the spectrum of the turbulence is changed is observed, which is in quantitative agreement with the theoretical prediction. It is also revealed that the turbulent waves are far more effective than the monochromatic waves in increasing the effective collisions