Spray gun for a direct-vision image storage tube and an image-storage tube using this gun

An adjustable memory-time direct vision image storage tube comprising in an evacuated envelope a record gun, a spray gun, a memory surface, and a luminescent output screen, the duration of the memory of said tube being adjusted by including means for providing a d.c. potential on a control grid of said spray gun, said spray gun comprising cathode means for producing a beam of electrons;

• said control grid being associated with said cathode for controlling the density of the said electron beam in accordance with the d.c. potential;
• accelerating electrode means for accelerating said beam of electrons and including means for accelerating said beam of electrons and including means for receiving potential which is constant;
• quadraopolar lens means positioned about the path of the accelerated beam, and formed by two pairs of flat plate electrodes occupying four of the faces of a parallelepiped, with the electrodes of a pair being opposite one another, and the electrodes of the pairs being perpendicular to one another about the beam;
• means for applying a greater potential to one of said pairs of electrodes than to the other of said pairs of electrodes, for causing said beam to form a spray shape beam;
• said means for providing the adjusted potential on said control grid thus controlling the density of the electrons in the spray beam, and an image's duration on said tube being proportional to said beam density.