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TY - CONF AU - Bahrdt, J. AU - Holldack, K. AU - Kuske, P. AU - Müller, R. AU - Scheer, M. AU - Schmid, P.O. ED - Petit-Jean-Genaz, Christine ED - Arduini, Gianluigi ED - Michel, Peter ED - Schaa, Volker RW TI - Undulator Photon Beams with Orbital Angular Momentum J2 - Proc. of IPAC2014, Dresden, Germany, June 15-20, 2014 C1 - Dresden, Germany T2 - International Particle Accelerator Conference T3 - 5 LA - english AB - Photons carrying orbital angular momentum (OAM) are present in the off-axis radiation of higher harmonics of helical undulators. Usually, the purity and visibility of OAM photons is blurred by electron beam emittance. However, high brightness OAM beams are expected in ultimate storage rings and FELs, and they may trigger a new class of experiments utilizing the variability of the topological charge, a 3rd degree of freedom besides wavelength and polarization. We report on the first detection of OAM photons in helical undulator radiation in the 3rd generation storage ring BESSY II. Measurements and simulations are compared and the impact of emittance and energy spread is discussed. PB - JACoW CP - Geneva, Switzerland SP - 213 EP - 215 KW - undulator KW - emittance KW - photon KW - experiment KW - storage-ring DA - 2014/07 PY - 2014 SN - 978-3-95450-132-8 DO - 10.18429/JACoW-IPAC2014-MOPRO057 UR - http://jacow.org/ipac2014/papers/mopro057.pdf ER -