Schmidt, O.A. Gluskin, E. Jensen Jr., D.P. Pile, G. Strelnikov, N.O. Suthar, K.J. Trakhtenberg, E. Vasserman, I. Xu, J.Z. JACoW Publishing Geneva, Switzerland 978-3-95450-188-5 10.18429/JACoW-MEDSI2016-WECA04 English 288-292 WECA04 ion undulator controls vacuum alignment Contribution to a conference proceedings 2017 2017-06 https://doi.org/10.18429/JACoW-MEDSI2016-WECA04 http://jacow.org/medsi2016/papers/weca04.pdf The Horizontal-Gap Vertically-Polarizing Undulator (HGVPU) is a compact, innovative, variable-gap insertion device developed by Argonne National Laboratory for the LCLS-II HXR beamline at SLAC. A full sized 3.4-meter-long prototype has been built and fully tested meeting all LCLS-II undulator specifications. An array of conical springs compensates the attractive magnetic forces of the undulator jaws. These springs are designed to exhibit non-linear spring characteristics that can be closely tuned to match the force curve exerted by the magnetic field, thereby minimizing the overall deflection of the strongbacks. The HGVPU also utilizes the existing LCLS-I support and motion system along with other existing equipment and infrastructure, thus lowering overall cost and installation downtime.