Magnesium Diboride Short Period Helical Undulator for the International Linear Collider Positron Source

The positron supply for the International Linear Collider (ILC) will be generated by shining a 285 kW beam of 10.7 MeV photons onto a metallic target. The photons themselves are to be generated from a series of 100 2-meter-long, short-period, double-helical undulator units. This project will design and construct this short-period helical undulator for the ILC. Magnesium diboride (MgB2) will be used as strand material for the winding of such undulators, due to MgB2's high operating temperature margin (Tc = 29 K) and radiation tolerance. In Phase I, a planar undulator cell will be designed for operation at temperatures of up to 10-15 K. The four-coil set will be based on a period of 14 mm, and a field of 1 T within a 6 mm gap. Suitable formers will be constructed and the coils will be wound with s-glass insulated strand, heat treated, and vacuum impregnated. In Phase II, a model helical undulator for the ILC positron source will be designed, and a short period double helical undulator will be constructed and tested. Based on the design, coil formers will be constructed from copper, and the coils will be wound, impregnated, and tested for current carrying capacity and field generation. Commercial Applications and other Benefits as described by the awardee: In addition to the ILC application, the magnesium diboride strand, with relatively high thermal margin and radiation tolerance, should find other near-term accelerator applications in the winding of light-source wiggler and undulator magnets. On the commercial side, MgB2 is being considered for MRI; motor, transformer, and gyrotron-magnet windings; and metal targets exposed to a high intensity photon beam.