A model superconducting helical undulator fabricated using a small filament, tube-type, multifilamentary Nb₃Sn wire

Abstract

A model helical undulator 250 mm in length, designed and fabricated with a period of 14 mm, was tested in a liquid helium bath. The helical coil was wound with a multifilamentary, tube-type Nb 3 Sn strand with 217 sub-elements. The coil I c and the magnetic field in the bore were measured at 4.2 K in a liquid helium bath using a Hall probe. I c was found to be 842 A, and the bore field reached the design specification of 0.8 T. The transverse bore field was also measured as a function of position along the length of the undulator axis and was seen to exhibit the expected sinusoidal behavior. The measured I c was compared with that obtained from a crossing of a load line (determined from FEM modeling) with the I c (B) curve of a short sample Nb 3 Sn strand. The coil exhibited the same critical current as the short sample.

Review and prospects of world-wide superconducting undulator development for synchrotrons and FELs

“…A short Nb 3 Sn helical SCU14 model with return-peg design, as shown in figure 3, was first constructed by Kim et al in 2007 for the ILC positron source project; it is based on the wind-and-react technology and reached an on-axis field B 0 of 0.9 T at 7.94 mm magnetic bore after training quenches [21]. With similar configuration, Majoros et al fabricated another two short models: one reached a low B 0 of 0.314 T due to unexpected flux jumps and the other reached an enhanced B 0 of 0.8 T by using small-filament Nb 3 Sn wires [22,23].…”

Current status and future perspectives of accelerator-based x-ray light sources

“…It is well known that an alternative material, Nb 3 Sn, is available for the SC wires, whose critical temperature (18.3 K) is nearly double of that of NbTi (9.5 K), and the critical current is a factor of two higher than that of NbTi at 4.2 K, suggesting the potential of shorter-period SCUs based on this material. In practice, R&D efforts have been made for more than a decade to develop Nb 3 Sn-based SCUs [145,146]. Although they have not been tested under practical conditions in the storage ring, realization of them may lead to a breakthrough in the development of SCUs.…”