Energy spectra of plasma self-emission recorded in the soft X-ray, as measured by the VSG diagnostic for B = 20 T (top row) and B = 30 T (bottom row; in the 30 T case for 15° and 30° the lighter band around z = 3 − 4 mm is an artefact due to a local loss of sensitivity of the detector which was used for these shots). These are raw data corrected for the detector (image plate) response to the X-rays and for the grating reflectivity, which is dependant on the X-ray energy (see text).