Excitation of large-amplitude ion-wave wake fields

Plasma wake fields in the ion-wave regime have been excited by injecting ion bunches with a variety of shapes. An excited-wave amplitude ({δ}n/n₀) of up to 17% has been observed for a bunch falloff time less than the wake-field period. The large-amplitude wake wave damps out, along with oscillations of the wave envelope. A simple linear theoretical model is developed, which can explain most of the observed phenomena, except for the large-amplitude oscillations.