PURPOSE: To prevent generation of a halo and improve resolution of a picture on an overall screen by making both outside electron beams to excessively be underconcentrated at the center of the screen followed by being concentratedly corrected by means of a quadruple magnetic field of a static concentrator commonly used.

CONSTITUTION: When electron beams BR and BB on both sides are concenratedly corrected to the side of the central electron beam BC, each electron beam receives push power in the left and right directions from a magnetic field in the direction of a horizontal axis and vertical outward attractive force in the direction of a vertical axis as shown by an arrow. On the horizontal axis both outside electron beams BR and BB receives respectively force toward the central electron beam BC and travel each other to the side of the central electron beam BC. When concenratedly corrected in a quadruple magnetic field of a static concentrator 6, deflection strain of the electron beam received from the deflection magnetic field of a self-convergence system is compensated to reduce the halo generation and remarkably improve overall resolution of the scanning picture on a screen.