The spot size and focal length of a one‐eighth betatron wavelength final focusing cell with a nonuniform current density distribution are predicted. The final focusing cell is modeled with an azimuthal magnetic field distribution that varies asrN. A Lie transform method is used to determine the behavior of the ion beam as it passes through the focusing cell. The analysis indicates that a final focusing cell with a current density distribution that is strongly concentrated at the channel edge focuses the beam much less efficiently than a channel with a uniform current density distribution, and provides a scaling relation for the focused beam radius:rfoc∝rc(Ic/If)1/2N, wherercis the unfocused beam radius,Ifis the discharge current in the focusing cell, andIcis the discharge current in the transport channel.