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. Developing a MgB2 SCU operating at ~12 K, enables the use of a LHe free dry conduction cooled system. Phase II efforts finalized all the thermomechanical design details of the 0.3m MgB2 SCU, refined the magnetic simulation to tune the first and second integrals, established a test bed for key components, developed a pulsed wire test bench and is currently fabricating the full system. The final phase II undulator operating point is designed to be cryogen free and have a period of 15 mm, with an in wire current density Je of 878A/mm^2, operate at 7.5 K in a self-field of 2.1T and a pole gap of 5 mm to generate a 1.13T axial field resulting in a k=1.6. The goal for the Phase IIA project is to scale up the developed processes and techniques to produce, assemble, magnetically tune and test under the operational power load the full scale, a 1-m long MgB2 SCU section. To this end an upgrade of the cryogenic system and magnetic metrology systems are proposed as the main thrust of the project. These new types of SCU insertion devices can entertain considerable and continuous demand at the Synchrotron Light Source and X-ray Free Electron Laser facilities as it would permit the construction of a device that does not require a LHe supply. This would enable implementation and testing of such a SCU locally at one beamline location, without the major upfront cost of developing a facility-wide cryogenic infrastructure and thus well worth the investment. Further, paired with ongoing wire developments, this device could significantly extending towards hard x rays the keV – 20keV spectral range covered by undulators in the medium and high energy synchrotron light source facilities.