Ultra-Short-Period Undulators for the Next Generation X-ray Free Electron Lasers

There is a growing interest on the compact XFELs to be used in applications such as medical science (surgery, fat removal), material science and military. In order to build a compact XFEL, constructing an undulator with sub-millimeter period (λ_u) is mandatory. Many problems arise due to miniaturization of undulators; such as keeping the magnetic field high while still having a considerable gap to minimize beam scraping. In this work, RADIA program has been employed for the modeling of sub millimeter period undulators (20 µm < λ_u < 400 µm) with three different magnet configuration; namely Up-Down (↑↓↑↓…), Halbach (Wiggler) (↑→↓←↑…) and Hybrid (→↑←↓→…). Effects of sub-millimeter undulator period and gap on the magnetic field pattern of the undulator have been discussed.