First spectral measurements of a cryogenic high-field short-period undulator oleh F. Holy, A. R. Maier, B. Zeitler, R. Weingartner, S. Raith, N. Kajumba, M. El Ghazaly, W. Lauth, D. Krambrich, A. Gaupp, M. Scheer, J. Bahrdt, F. Grüner