How to get a separatrix branch with low divergence at 1/3-integer resonant beam slow extraction

Consideration is given to the separatrix dependent on chromaticity in 1/3-integer resonance. It means that the outgoing separatrices do not overlap for different momentums, in other words, they appear to be smeared. It is desired to get a separatrix branch with low divergence at the septum position in order to minimize the particle losses on it. W. Hardt (1981) proposed the method for compensation of this effect by introducing nonzero dispersions in the beam extraction straight section. But in his formula only global chromaticity is included and not local chromaticity. Formulas are proposed using analytic techniques for solving this problem including both global and local chromaticity effects.<>