Eddy currents induced by deflection fields in electron guns of cathode ray tubes

Nowadays an optimal design of a combined system of an electron gun and a deflection coil in cathode ray tubes is demanded. Therefore, an analysis is necessary of the effects on electron beam optics of eddy currents in the conducting parts of an electron gun, induced by the magnetic deflection field. Such an analysis, based on numerical calculations and verified by experiment, is presented in this paper. The analysis of the transient behaviour of the induced eddy currents shows that a steady state is reached on a μsec time scale and that the steady-state solution can serve to determine the most important effects on the electron optics. It appears that, in general, both for homogeneous and realistic (inhomogeneous) deflection fields, the influence of the induced fields on the convergence of the electron beams is very small (<50 μm)