Praseodymium Undulator with Textured Dysprosium Poles for Compact X-ray FEL Applications

There is a strong interest in the synchrotron radiation community in developing insertion devices with shorter periods and higher fields. Historically, this has been driven by the synchrotron radiation users demand for higher-brightness hard X-ray fluxes from 3rd Generation Light Sources. Recently, the emergence of X-ray FELs and growing interest towards ultrafast compact soft X-rays facilities, require even shorter period ( & lt; 1 cm) undulator structures. In both cases, the desired undulator parameters are outside of the performance envelope of the conventional permanent magnet in-vacuum undulators, hence new materials and new design approaches are being sought for. This project seeks to develop a novel high peak field, ultra-short period undulator using two unconventional materials: praseodymium iron-boron permanent magnets (PrFeB) and textured dysprosium (Tx Dy) ferromagnetic field concentrators. Both materials exhibit extraordinary magnetic properties at cryogenic temperatures, such as very large energy product and record high induction saturation, respectively. The undulator planned to be built in Phase II will significantly surpass the state-of-the-art and offer an ideal solution for the next generation of compact X-ray light sources. In the Phase I, we experimentally demonstrated feasibility of using Tx Dy poles in a hybrid undulator configuration with PrFeB magnets, achieving 1.4 T on axis field in a 9 mm period undulator (K ~ 1.2). In the Phase II we plan to optimize the Tx Dy pole production process, and fabricate and characterize a complete flange-to-flange prototype undulator system, with period of 7 mm and a peak field on axis of about 1.5 T. Commercial Applications and Other Benefits: Practical realization of the proposed device will significantly surpass state-of-the-art and offer an ideal solution for the next generation of compact X-ray light sources, as well as for some of the most demanding applications at conventional storage ring based synchrotron radiation sources. In addition, the proposed undulator device offers a high added value application for the two new materials, PrFeB and Tx Dy.