Development of Superconducting High Heat-Load Undulator

The development of superconducting undulators (SCU) that can stably operate at shorter periods and higher peak fields require designs with smaller gaps. These smaller gaps devices can be subjected to higher heat loads due to increased sensitivity to resistive wall impedances, beam losses, geometric impedance contributions and synchrotron radiation heating. Consequently, short period SCUs should ideally be designed to operate at higher temperatures where the cryo-cooling capacities are larger. Most SCUs developed to date utilize NbTi superconducting wire, which can only be operated at the liquid helium temperatures (< 4.2 K), and thus are very sensitive to the warm core effects. MgB2 is a metallic superconductor with a transition temperature of around 39 K, significantly higher than NbTi or even Nb3Sn. The material also does not suffer from an unstable superconducting state at large currents or fields. Recent progress in the development of the 2nd generation MgB2 with much increased critical current, makes this material a promising new contender for the SCU applications. If one can develop a MgB2 SCU operating at > 12 K, Gifford- McMahon cryocoolers can be used which are less expensive and offer superior cooling capacity compared to their liquid helium counterparts operating below 4.2 K. Phase I of this project will entail the design, simulation and cryogenic system engineering of the SCU prototype device that will utilize MgB2 wire, along with the construction of a sample wound module to gain familiarity with the manufacturing and validation needs. Phase II efforts will manufacture and validate the requisite 0.3m device at RadiaBeam, including field characterization in a cryogenic environment. The undulator will target a period between 12 and 15 mm, with a current density =1500A/mm2, a self-field of 2-3 Tesla, and pole gap of ~ 5 mm. This effort will forge a path towards the production of MgB2 SCU for a medium-energy storage ring. Short gap MgB2 wire based SCU operating at sufficiently high temperatures such that a liquid cryogen free system could effectively remove the heat load from a high repetition rate electron beam, would offer considerable value to the synchrotron light source and X-ray FEL capabilities, by significantly extending the coverage and brightness of the light source facilities.