Ion Energy Increment by Ion Acoustic Waves

An ion energy increment by externally excited ion acoustic waves has been studied in a simple double plasma device. The energy increment was measurd in detail by means of a small electrostatic energy analyzer whose resolving power was better than 0.1 eV. A small energy increment of about 10% was observed under the condition where ion fluctuations caused by the wave fields were less than 10% and the ratio of the electron-to-ion temperature was about 10. The measured energy increment was approximately proportional to the wave frequency and to the square of the wave potential. The fact is well understood if the wave energy is transferred to the ions through the Landau damping. The electron energy increment, however, was negligible in accordance with the above interpretation.