Narrow Beam Tube e/m
Narrow Electron Beam Tube The specific electron charge e/m can be determined quantitatively with this tube. A spherical chamber contains an electron beam system consisting of an indirectly heated oxide cathode, a perforated anode, and a Wehnelt cathode. The chamber also contains neon at a residual gas pressure of approx. 1.3 Pascals. Description The gas atoms are ionized by the electrons and glow when excited, producing a visible beam along the electron flight path. The electron beam can be bent into a circle in the uniform magnetic field of the Helmholtz coils, KA6021. Graduations inside the tube, via a stepped ladder, permit parallax-free adjustment of the circle diameter. Reducing the current to the cathode will focus the beam. The tube is mounted on a base plate allowing for all the electrical connections to the tube.