  The standard design method for conventional straight dipole magnets is
improved in this paper. The good field region is not symmetric with respect to
the magnet mechanical center, and its width is not enlarged to include the beam
sagitta. The integrated field quality is obtained by integrating the field
along nominal beam paths. 2D and 3D design procedures of the improved design
method are introduced, and two application examples of straight dipole magnets
are presented. It is shown that the differences in integrated field quality
between different field integration paths cannot be neglected. Compared with
the traditional design method of straight dipole magnets, the advantage of the
improved method is that the integrated field quality is accurate; the pole
width, magnet dimension and weight of a straight dipole magnet can be reduced.
