To measure the beam polarization the Møller scattering technique will be used. Longitudinally polarized beam electrons will scatter from a target which contains longitudinally polarized atomic electrons. The counting rate of the scattered electron depends on whether the spins of the electrons are parallel or anti-parallel. The ratio of the two counting rates is a measure for beam polarization:
where 
and 
are the beam and target polarization,
the asymmetry coefficients. For energies higher than 1 GeV, there are only
three non zero asymmetry coefficients 
= -1/9, 
= +1/9 and
= -7/9 (maximum values).
Background under the Møller peak is dominated by Mott scattering and its radiative
tail. To reduce this background the coincidence technique will be used by detecting
scattered and recoiling electron in coincidence. The easiest geometry corresponds to
a detection under 90 
CM. there has its maximum and the cross
section is (independent of energy)
For energies between 1 and 6 GeV the corresponding 90 CM angles are in the
range 1.8 
to 0.75 in the lab frame.