Magnetic field of superconductive in-vacuo undulators in comparison with permanent magnet undulators

During the last few years superconductive undulators with a period length of 3.8 and 14 mm have been built. In this paper scaling laws for these novel insertion devices are presented: a simple analytic formula is derived which describes the achievable magnetic field of a superconductive undulator as a function of gap-width and period length.