Overview of hot topics in insertion device design

Emphasis in insertion devices (undulators and wigglers) is evolving. Conventional designs account for the majority of devices in use as synchrotron radiation (SR) or free-electron laser (FEL) sources, but more is being demanded with each succeeding application. Totally passive field compensation, gap independence, and the perfecting of phase and spectral properties are areas of major interest. However, the shift toward specialty designs is increasingly important. Designs are tailored to achieve specific radiation characteristics. These range from SR sources with time-dependent polarization capabilities to long devices optimized for FEL operation in the X-ray regime. Strong focusing and other beam dynamics related characteristics are becoming extremely important for the next generation of FEL devices. As electron beam quality continues to increase, small-gap, small period, and unconventional field profiles are becoming necessary for compact sources. These areas of increased interest are examined.