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In this paper, the authors describe an aging process to solve the unbalanced emission slump, which does not need any change in the electron gun design. The principle is to apply a high frequency (HF) magnetic field on the electron gun during the aging process. The effect is that the scanning electron beam and the HF magnetic field heat up the gun parts by electron bombarding and eddy current heating. In this way the grids are effectively degassed. A part of the desorbed gases is pumped by the Ba-getter in the tube, whereas another part is ionized by electron collision. These ionized gas molecules, notably Ar+, are partially trapped in gun parts. Therefore a lower residual gas pressure can be achieved. According to the theoretical and experiment results, we may conclude that the application of a magnetic ion trap during aging can improve the emission slump of the central beam and gas pressure in the tube significantly. The heating of the electron gun by an HF-coil or the DU in a pull back position during aging is rather easy to implement in a CRT factory.