Progress in undulator engineering for synchrotron radiation applications

Abstract Advances in performance and design have been made since the first STI (Spectra Technology, Inc.) undulator was built in 1980. Design enhancements have increased the performance achieved in undulators. These enhancements have produced successively higher and more uniform magnetic fields. The wedged-pole hybrid design has been demonstrated to yield the highest magnetic field to date for a given gap-to-wavelength ratio. A simple shim tuning method of reducing magnetic-field errors has demonstrated the best field uniformity to date. The field uniformity achieved with this tuning technique is the most insensitive to gap changes of methods reported to date. Progress in mechanical design and magnetic measurements have resulted in enhanced serviceability and adaption. These enhancements and their implications on STI's most sophisticated undulator, NISUS (near-infrared scalable undulator system), will be discussed.