The IMBL wiggler source produces different spectra, depending on the magnetic field that is used. The IMBL characterisation paper written by Dr. Andrew Stevenson is the primary source for this information [1]. As a guide, the spectral brightness curves for different fields is given in the figure below.
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[1] Stevenson, A.W., et al., Quantitative characterization of the X-ray beam at the Australian Synchrotron Imaging and Medical Beamline (IMBL). Journal of Synchrotron Radiation, 2017. 24: p. 110-141.