  Using 2d3v code LCODE, the numerical simulation of nonlinear wakefield
excitation in plasma by shaped relativistic electron bunch with charge
distribution, which increases according to Gaussian charge distribution up to
the maximum value, and then decreases sharply to zero, has been performed.
Transformer ratio, as the ratio of the maximum accelerating field to the
maximum decelerating field inside the bunch, and accelerating the wakefield
have been investigated taking into account nonlinearity of the wakefield. The
dependence of the transformer ratio and the maximum accelerating field on the
length of the bunch was investigated with a constant charge of the bunch. It
was taken into account that the length of the nonlinear wakefield increases
with increasing length of the bunch. It is shown that the transformer ratio
reaches its maximum value for a certain length of the bunch. The maximum value
of the transformer ratio reaches six as due to the profiling of the bunch, and
due to the non-linearity of the wakefield.
