  A quantum fluid model is used to describe the interacion of a nondegenerate
cold relativistic electron beam with an intense optical wiggler taking into
account the beam space-charge potential and photon recoil effect. A nonlinear
set of coupled equations are obtained and solved numerically. The numerical
results shows that in the limit of plasma wave-breaking an ultra-high power
radiation pulse are emitted at the$\gamma$-ray wavelength range which can reach
an output intensity near the Schwinger limit depending of the values of the FEL
parameters such as detuning and input signal initial phase at the entrance of
the interaction region.
