Amplification of ion-acoustic solitons by an ion beam

Ion-acoustic solitons in a plasma traversed by a weak ion beam are studied experimentally by a double plasma device. Large amplitude compressive pulses are amplified and steepened to become solitons of which the amplitude n/nsub(o) is comparable or less than 40%. The amplitude of the soliton is maximum at a beam velocity of Vsub(b)/Csub(s) = 1.7 while the linear growth rate is maximum at Vsub(b)/Csub(s) = 1.3. Theoretical explanations are presented with the use of the fluid model. (author)