In GAMMA 10, plasma was generated and heated by conventional ICRF systems (RF1, RF2). RF3 system with the 10th harmonic ion cyclotron frequency near the midplane of the central cell was applied for the high-density plasma generation. At the same time, a plasma heating by RF3 was observed. Wave damping was calculated by using the hot plasma distribution in infinite and homogeneous plasma. It is clearly seen the high-energy component is important for the damping of high harmonic fast waves. The experimental observations in GAMMA 10 suggest the existence of high-energy tail in the energy distribution of ions.