Theoretical and computer simulation models of plasma wakefield acceleration often do not take into account the ion motion, considering ions immobile due to the large mass. This approximation is inapplicable in the cases of intense or long drivers, or a large distance between the driver and the witness. In such cases, the ions can move so that the disturbance of the ion density makes significant changes to the field map at the witness location. Accounting for this factor usually leads to a lower amplitude of the electric field in the wake and rapid damping of plasma oscillations.
There are, however, conditions in which ion motion leads to an increase in the amplitude of the accelerating field on the axis. This occurs in a weakly nonlinear wakefield due to the redistribution of its energy over the plasma cross section. The effect can be identified by visualizing the energy flow in the wave. Under certain conditions, an increase in the longitudinal field, as compared with the immobile ions case, can reach 20%.
|Working group||Theory and computation|