Evaluation of Magnetic and Mechanical Properties of Delta Undulator

The paper describes a test result of a Delta undulator prototype recently built at CLASSE (Cornell Laboratory for Accelerator-based Sciences and Education). This undulator design is optimized for the linac type beam. It has a round bore, very compact, provides full polarization control and has magnetic field significantly stronger than in a conventional undulator. We are planning to use Delta undulator in the Cornell Energy Recovery Linac (ERL) facility, but it can also be employed in FEL (Free Electron Laser) and ILC (International Linear Collider) facilities. The tested prototype was 30cm long with 5mm round gap, 24mm period magnetic structure was assembled with NdFeB (40SH) permanent magnet blocks. The model demonstrated a 1.25T maximum peak field in planar mode and 0.85T in helical. That is approximately 90% of the design value. Calculation of the photon flux spectrum for ERL type of beam using the measured field indicated less than 3% of flux degradation due to the field errors in helical mode and ∼ 20% in planar. In the paper we describe results of magnetic field measurement as well as measurement of structure deformation. Analysis of the deformation suggested improvements in mechanical structure that should bring the peak field up to design value and reduce field errors. This improvement will be implemented in the next model. Overall, the test result can be considered as a proof of principal of the Delta undulator magnets. PACS numbers: 85.70.-w, 41.60.-m, 07.85.Qe ∗ Work supported by National Science Foundation under contract DMR 0225180 †Mail send to: A. Temnykh, Wilson Lab, Cornell University, NY 14850, USA E-mail [email protected] , tel. +1 607 255 4882, fax +1 607 255 8062