Author Affiliations

C. Roedig,¹ G. Doumy,^1,2 S.-K. Son,³ C. I. Blaga,¹ A. D. DiChiara,¹ R. Santra,^3,4 N. Berrah,⁵ C. Bostedt,⁶ J. D. Bozek,⁶ P. H. Bucksbaum,⁷ J. P. Cryan,⁷ L. Fang,⁵ S. Ghimire,⁷ J. M. Glownia,⁷ M. Hoener,⁵ E. P. Kanter,² B. Krassig,² M. Kuebel,⁸ M. Messerschmidt,⁶ G. G. Paulus,⁸ D. A. Reis,⁷ N. Rohringer,⁹ L. Young,² P. Agostini,¹ and L. F. DiMauro¹

¹The Ohio State University, Columbus, Ohio 43210, USA

²Argonne National Laboratory, Argonne, Illinois 60439, USA

³Center for Free-Electron Laser Science, DESY, 22607 Hamburg, Germany

⁴Department of Physics, University of Hamburg, 20355 Hamburg, Germany

⁵Western Michigan University, Kalamazoo, Michigan 49008, USA

⁶Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA

⁷Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA

⁸Institute of Optics and Quantum Electronics, 07743 Jena, Germany

⁹Lawrence Livermore National Laboratory, Livermore, California 94551, USA