A scenario to verify the knock-on tail formation by energetic protons and the resulting enhancement of the fractional ion heating by using 3He-containing deuterium plasma is presented. On the basis of the Boltzmann-Fokker-Planck (BFP) model, the knock-on tail formation in deuteron distribution function due to nuclear plus interference (NI) scattering of fusion-produced energetic protons and the resulting modification of the neutron emission spectrum are examined. A recognizable change in the energetic-neutron emission rate due to the knock-on tail formation depending on the external 3He inclusion is shown. Another possible scenario to ascertain the enhancement of ion-heating by using -ray-generating 6Li+D reaction is also presented and discussed.