RADIABEAM TECHNOLOGIES, LLC — Department of Energy SBIR Phase II: C53-11a

Description

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 entailed 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. The final phase I undulator operating point was designed to be cryogen free and have a period of 15 mm, with an in wire current density Je of ~800A/mm^2, operate at 10K in a self-field of 1.85T and a pole gap of 5 mm to generate a 1.14T axial field resulting in a k=1.6. Further as we are wire vendor agnostic, as the wire material development is progressing rapidly, we can nimbly adjust our design based on the best offering available during potential Phase II execution. If successfully demonstrated, these new type of SCU insertion devices can become a successful product, entertaining a 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 may not require a continuous LHe supply from the very beginning. This would enable to start implementation and testing of such an 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, this device could significantly extend towards hard x rays the spectral range covered by undulators in the medium and high energy synchrotron light source facilities.