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 and Development of a Superconducting Helical Undulator for a Polarized Positron Source
A small test model superconducting helical undulator for the production of 20 MeV photons has been constructed and tested. The undulator has a period of 14 mm, a bore of approximately 4 mm and produces a magnetic flux density on-axis of 0.8 T as required by the TESLA facility. Work is now underway to modify this design to meet the requirements of the ILC positron source and to manufacture a full scale prototype. This paper details the design, construction and measurements of the small test model and the modeling work necessary to extend that design for use in the ILC
Uncorrelated Emittance Growth in the TTF-FEL Bunch Compression Sections due to Coherent Synchrotron Radiation and Space Charge Effects
In the bunch compressing sections of the Tesla Test Facility Free Electron Laser[1] (TTF FEL), short bunches travel on trajectories with small bending radii. Thus, coherent synchrotron radiation (CSR) will play a significant role in beam dynamics. The energy loss of the bunch will vary longitudinally as well as transversally across the bunch and will induce an emittance growth. The occuring transversal forces, especially the so-called “Talman force” ([3]) and its effects on emittance have been treated before analytically for some specialized arrangements ([2, 4]). The emittance growth will affect the projective as well as the slice emittance (i.e., the emittance of sub-ensembles of particles with equal longitudinal position). The computer simulation code TraFiC4 calculates the fields in the bunch from first principles, thus taking into account radiative as well as space charge effects, which are inseparable on curved trajectories. In addition to dealing with longitudinal dynamics [5], this code has now been extended to handle the transversal dynamics of the bunch. We use it to study the behavior of the fields across the beam and the resulting slice and projective emittance growth. We study its dependence on bunch parameters such as charge and shape and investigate possible cures by shielding.