ELECTRON GUN, CATHODE RAY TUBE, AND PICTURE DISPLAY DEVICE

摘要

The invention relates to an electron gun 100 for use in a cathode ray tube. The electron gun 100 has an electron source 10, a body 20 with a transmission cavity 25 of which the wall 28 is at least partly coated with an electrical insulator for the emission of secondary electrons, and an electrode 30 for applying a first electric field between the entrance 26 and the exit 27 of the cavity. The electron gun is characterized in that it comprises means for preventing the travelling of positive ions, which are formed by collisions of electrons that have exited from the cavity 25, in reverse direction along the same path as the electrons and colliding with the module 20. Such collisions can damage the cavity exit 27 or the electrical insulator on the wall 28. This is undesirable because the current density of the electron beam 101 exiting from the cavity 25 will deteriorate.