[en] Recently the authors completed a design of the second-harmonic (i.e., N = 2) central region of the Princeton University AVF cyclotron which will replace the existing one. The study for this new central region was motivated from the fact that the single-turn extraction for N = 2 beams has never been satisfactory in our cyclotron. Through the beam orbit dynamics studies, it was found that the problem was due to the combination of an over-sensitive phase-dependent orbit centering error and large energy speed at the position of radial beam defining slit. In the new design, the authors reduced these problems. This paper describes the design procedure and result