Insertion Device Upgrade Plans at the NSLS

This paper describes plans to upgrade insertion devices (IDs) at the National Synchrotron Light Source (NSLS), Brookhaven National Laboratory, U.S.A. The aging wiggler (W120) at X25 is being replaced by a 1 m long in-vacuum mini-gap undulator (MGU-X25) optimized for a dedicated macromolecular crystallography program. A new, 1/3 m long, undulator (MGU or SCU-X9), will be installed between a pair of RF cavities at X9, and will serve a new beamline dedicated for small angle x-ray scattering (SAXS). Both IDs will have provision for cryocooling the NdFeB hybrid arrays to 150K to raise the field and K-value and to obtain better spectral coverage. Design issues of the devices and other considerations, especially magnetic measurement at low temperature, will be discussed.