Speaker
Description
The Helmhotz-Zentrum Berlin (HZB) is developing an elliptical in-vacuum undulator, IVUE32, following the APPLE-II design with a magnetic force compensation concept. The undulator will be installed in the BESSY II storage ring. It will feature a 7 mm minimum gap and four magnet rows that can be moved to adjust the polarization of the synchrotron radiation. This shift movement requires a complex taper structure and a longitudinal slit in the shielding foils.
Extensive CST wakefield simulations have been conducted to investigate the interaction between the undulator and the beam. The impedance of the device on the beam is studied, as well as the heating of the undulator induced by the beam.
The taper structure has to compensate for two axes of motion. The vertical gap movement and the longitudinal shift movement. The shift movement is different for each half of the shielding foil. Previously presented designs used separate foil tensioning systems to independently compensate for the two axes of motion.
A length constraint due to the $\beta$-function might prohibit the separate compensation. Changing the gap while also compensating for the shift motion introduces an asymmetry in the taper, where the shielding foils have different gradients.
Different asymmetric tapers are studied to find the limits for horizontal impedance for the BESSY II beam.
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