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.
Development of a MODEL superconducting helical undulator for the ILC positron source
The helical undulator for the proposed International Linear Collider (ILC) positron source requires high-permeability steel poles and superconducting coils to meet the ILC parameters. A short-model undulator with a period of 14 mm was designed, fabricated including high-permeability steel poles, and tested in LHe. The ends of the model were designed to wind the Nb3Sn double helix without any conductor joints. After a few quenches in the first excitation test, the current density in the coil reached 1.28 kA/mm2, which was approximately 90% of the estimated short-sample critical current density. The periodic on-axis fields were mapped at two azimuth angles. Excluding the end fields, the standard deviation of the field amplitudes and higher harmonic coefficients for the periodic field were less than 7times10-3 and 5times10-3, respectively.
Simulation study of high power microwave generation by virtual cathode oscillation in coaxial vircator
Summary form only given, as follows. We have numerically simulated the high power microwave generation by virtual cathode oscillation in a coaxial vircator with 3 dimensional PIC code Magic. It is noted that the coaxial vircator has the advantage of an enhancement of power efficiency and gaining of narrow bandwidth frequency. The study is focused on the design of a diode structure for a coaxial vircator suitable for Chundoong IREB pulser (Max. 600 kV, 85 kA, 60 ns). It consists of a center annular cathode, a cylindrical meshed-anode and a reflector. The simulation results showed that the coaxial vircator can indeed be operated at the selected frequency with the narrow bandwidth and the microwave output power strongly depends on the position and geometry of the reflector. From this simulation results we expect that the maximum microwave output power will be obtained by the reflector of 4 cm in width and also 4 cm in distance away from the IREB, where the resonant frequency of microwave from coaxial vircator is simulated to be 6.577 GHz.