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  Bahrdt, J.; Bakos, J.; Gaebel, S.; Gottschlich, S.; Grimmer, S.; Knaack, S.; Kuhn, C.; Laube, F.; Meseck, A.; Rethfeldt, C.; Rial, E.C.M.; Rogosch-Opolka, A.; Scheer, M.; Volz, P.I.: The Status of the In-Vacuum-APPLE II Undulator IVUE32 at HZB / BESSY II. In: Frank Zimmermann ... [Ed.] : IPAC2022 : Proceedings of the 13th International Particle Accelerator Conference, in Bangkok, Thailand, 12–17 June 2022Geneva: JACoW, 2022. - ISBN 978-3-95450-227-1, p. THPOPT052/1-3
  https://jacow.org/ipac2022/papers/thpopt052.pdf

Open Access Version

Abstract:
At BESSY II, two new beamlines for RIXS and for X-Ray-microscopy demand a short period variably polarizing undulator. For this purpose, the first in-vacuum APPLE undulator worldwide is under construction. The parameters are as follows: period length=32mm, magnetic length=2500mm, minimum gap=7mm. The design incorporates a force compensation scheme as proposed by two of the authors at the SRI2018. All precision parts of the drive chain are located in air. New transverse slides for the transversal slit adjustment have been developed and tested. Optical micrometers measure the gap and shift positions, similar to the system of the CPMU17 at BESSY II. They provide the signals for motor feedback loops. A new UHV-compatible soldering technique, as developed with industry, relaxes fabrication tolerances of magnets and magnet holders and simplifies the magnet assembly. A 10-period prototype has been setup for lifetime tests of the new magnetic keeper design. The paper describes first results of the prototype and other key-components and summarizes the status of the full-scale undulator.