Influence of magnetic field errors on the spectrum of the PETRA undulator

At HASYLAB at DESY, a first undulator beamline for the storage ring PETRA is under construction. Due to the low emittance of PETRA it will deliver very brilliant radiation in the energy range from 20 to 200 keV using the 1st, 3rd and 5th harmonic of this insertion device. The brilliance of the undulator radiation is very sensitive to the magnetic field errors which deteriorate the coherence of the emitted radiation and decrease the brilliance of the harmonics. Therefore, we investigated the influence of different types of field errors on the intensities of the 1st, 3rd and 5th harmonic. The results for the PETRA undulator are presented and discussed.