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Our test setup consisted of one Mott polarimeter mounted in the left Møller leg and a scintillation counter mounted in the right Møller leg. This counter records all events occuring on the Be target and their amplitude spectrum is shown in the figure below.

A representative amplitude spectrum of the scintillation counter, viewing directly the interaction spot of the 3 MeV electron beam at the Be target.

The highest peak corresponds to the beam electrons deflected on Be nuclei (Mott scattering on Be) and going into the right leg; its position on the axis can be used for energy calibration (3 MeV). The lower cusp is due to the symmetric Møller electrons entering the right leg (1.5 MeV). The rise towards the low channel numbers corresponds to the background only. All structures overlap due to a finite resolution of the scintillation counter. The purpose of this measurement was to determine the spectrum of electrons entering the Mott polarimeters.