Small-gap insertion-device development at the National Synchrotron Light Source--performance of the new X13 mini-ap undulator.

The National Synchrotron Light Source (NSLS) 2.8 GeV electron storage ring continues to set high standards in insertion-device research and development. The Chasman-Green NSLS lattice design provides for dispersion-free long straight sections in addition to a very small vertical β function. As the electron beam size is proportional to the square root of this function, a program to exploit this feature was undertaken more than a decade ago by implementing short-period small-gap insertion devices in the NSLS storage ring. The possibility of utilizing existing moderate-energy synchrotron radiation electron storage rings to produce high-brightness photon beams into the harder X-ray region have been realised using in-vacuum undulators. In this article the operation of a 1.25 cmperiod mini-gap undulator, operating down to a gap of 3.3 mm within the NSLS X13 straight section, is reported. It is the brightest source of hard X-rays in the energy range ∼3.7-16 kev at the NSLS, and replaces an in-vacuum undulator which had a more limited tunability. [ABSTRACT FROM AUTHOR]