For examining the deflection of electron beams in a uniform magnetic field using a pair of Helmholtz coils U8481500 and for the quantitative determination of the specific charge of the electron em. Glass vessel with integrated electron beam system, consisting of an indirectly heated oxide cathode, a Wehnelt cylinder and a perforated anode, in neon residual gas atmosphere with precisely set gas pressure and with integrated measurement marks for parallax-free determination of the diameter of the fine beam. Gas atoms are ionized along the electron path and produce a sharply defined, visible fluorescent beam. Tube mounted on base with color-coded connectors.