Characterization and long term operation of a novel superconducting undulator with 15 mm period length in a synchrotron light source oleh S. Casalbuoni, A. Cecilia, S. Gerstl, N. Glamann, A. W. Grau, T. Holubek, C. Meuter, D. Saez de Jauregui, R. Voutta, C. Boffo, Th. Gerhard, M. Turenne, W. Walter