  Some electroweak models with extended neutral currents, such as those based
on the $E_6$ group, lead to an increase of the $\bar{\nu}-e$ scattering cross
section at energies below 100 keV. We propose to search for the heavy Z' boson
contribution in an experiment with a high-activity artificial neutrino source
and with a large-mass detector. We present the case for the LAMA experiment
with a large NaI(Tl) detector located at the Gran Sasso underground laboratory.
The neutrino flux is known to within a one percent accuracy, in contrast to the
reactor case and one can reach lower neutrino energies. Both features make our
proposed experiment more sensitive to extended gauge models, such as the $\chi$
model. For a low enough background the sensitivity to the $Z_\chi$ boson mass
would reach 600 GeV for one year running of the experiment.
