In this letter we consider the effect of synchrotron radiation losses due t
o the betatron motion of the electron beam in its self-induced magnetic fie
ld in a plasma acclerator taking into account the charge neutralization fac
tor. The most favorable case is where the plasma density is smaller than th
e beam density. The contrary regime is strongly disfavored by the synchrotr
on radiation loss for beams with characteristics for TeV energies. In both
cases we find that upon increasing the plasma density the synchrotron losse
s kill the acceleration process, so that there are limitations on the maxim
um allowable plasma density. (C) 1999 Elsevier Science B.V. All rights rese
rved.