Recent advances in insertion devices

The demand for more and better insertion devices (IDs) at new third-generation synchrotron radiation facilities has prompted significant advances in ID technology. Since the advances are being made at different laboratories around the world, an overview is given here of this progress. The focus is on those results that apply to IDs in general rather than to those from one specific ID or laboratory. The advances fall into two general categories: those that reduce the net effect that the ID has on the particle beam, and those that enhance the quality of the emitted light spectrum. The need for these advances, the factors that are most important in achieving them, and the current state of the art are discussed