Development of a 3.8 Meter Variable Polarization Undulator (EPU)

The design of a Variable Polarization Undulator (EPU) of the four row, pure permanent magnet undulator and a length of 3.8 m is presented. The design requirements and mechanical difficulties for holding, positioning, and driving the magnetic arrays are explored. The structural and magnetic considerations that influenced the design are then analyzed. This undulator will be installed on a new beam line for materials science research, designated BL13 at Stanford Synchrotron Radiation Laboratory (SSRL) BL13 is being designed for the photon energy range from 250 to 1600 eV, and to utilize an undulator source that produces linear polarized radiation at variable azimuthal angles as well as both left and right circularly and elliptically polarized radiation.