ANL, Argonne, Illinois, USA
Superconducting planar undulator (SCU) technology has been developed and is currently in use at the Advanced Photon Source (APS). The experience of building and operating the first short-length, 16-mm period superconducting undulator, SCU0, paved the way for two 1-m long, 18-mm period devices, SCU18-1 and SCU18-2. The first of those undulators has been in operation since May 2015, while the second one replaced SCU0 in September 2016. The possibility of building planar SCUs with a high quality field has been demonstrated at the APS. The measured phase errors of SCU18-2 at the design operational current are only 2 degrees rms, for example. An FEL SCU prototype - a 1.5-m long, 21-mm period undulator - was also built and tested as part of an LCLS SCU R&D program. This undulator successfully achieved all LCLS-II undulator requirements including a phase error of 5 degrees rms. The superconducting undulator technology also allows the fabrication of circular polarizing devices. Currently, a new helical SCU is under construction at the APS. In addition, the concept of a novel Superconducting Arbitrarily Polarizing Emitter, or SCAPE, has been suggested and is now under development.
