Experiments on ion-acoustic solitons in a plasma

The velocity and width of ion-acoustic waves in a collisionless unmagnetized plasma are investigated both theoretically and experimentally. The solitary wave solutions obtained by a pseudo-potential (PP) method are compared with those of a Korteweg-de Vries (KdV) equation deduced by a reductive perturbation method including the finite temperature of ions. For the velocity of solitons, both results are nearly equal. The square of the width times the height is constant for KdV solitons; however, it decreases with the soliton height for the PP solitary waves. The experiment has been performed by a multi-dipole double plasma machine. The velocity and width of solitary waves are measured as a function of the amplitude which is estimated taking two components of electrons into consideration. Experimental results agree well with the predictions of the PP method.