A $\hbox{Nb}_{3}\hbox{Sn}$ -Based, Model Superconducting Helical Undulator Fabricated Using a Wind and React Process
A model helical undulator 250 mm in length, with a period of 14 mm, was designed, fabricated and tested. The helical coil was wound with multifilamentary, internal-Sn type Nba3Sn strand. The 0.7 mm OD strand was insulated with S-glass, wound onto the former, and reacted, after which the coil underwent vacuum epoxy impregnation. The beam aperture was 7 mm, the winding bore diameter was 8 mm, and the OD of the complete winding was 18 mm. The helical poles were made from 1016 low carbon steel, and projected slightly above the coil pack, with an OD of 19.06 mm. The coil Ic and the magnetic field in the bore were measured at 4.2 K in a liquid helium bath. The bore field was also measured as a function of position along the length of the undulator.
Design of ${\rm Nb}_{3}{\rm Sn}$-Based Short Period Model Superconducting Helical Undulator
Superconducting undulators are being constructed to satisfy an increasing need within the synchrotron radiation community for higher and higher energy photon beams. The paper focuses attention on the design of a helical undulator for the ILC photon (hence positron) source. Finite element method (FEM) modeling was performed to extend the design of our existing 14 mm period undulator design to shorter periods with a view towards the final design, construction and testing of a 10 mm undulator. To launch this task we modeled the properties of 10 mm period undulators formed around bore tubes of the 6 mm and 8 mm OD with winding-pack cross-sections of 3 mm × 6 mm and 3 mm × 11 mm. These windings do allow a pole width of 2 mm and can take advantage of the corresponding about 0.2 T field increment due to it. In order to reach the target bore field of 1.1 T it is necessary to either reduce the bore size and tighten the associated tolerances, or to use a higher performing strand. In the present work we have chosen to optimize the undulator design basing it on the properties of an advanced tube-type strand keeping the bore tube diameter at 6-8 mm in order to see the needed performance to meet this undulator specification.
Cooperative Collection Development
The author discusses cooperative collection development from an historical perspective and examines some of the projects conceived and implemented during the past forty years. In many cases the projects failed even after years of concentrated effort. However, more important than these failures are new efforts that are being made. The major focus of this article is on both current regional projects and the more broadly based ARL-sponsored North American Collections Inventory Project. The author discusses these efforts and offers some specific judgments regarding the possibility that these projects will lead to a truly successful coordinated collection development project on a national basis.