Top: loop width FWHM W found from Vis_FwdFit over the same energy ranges as for the (x,y) peak positions shown in Fig. 5. The average width or vertical size of an X-ray source in the radial direction R is . The width was also found using three larger energy bins of 10–12.5 keV, 12.5–18 keV and 18–25 keV, increasing the number of counts and hence reducing the uncertainty. This gives an average width of . Bottom: CLEAN (red) and Vis_FwdFit (blue) image profiles along a line perpendicular to the solar surface and through the centroid position of the coronal source, for the energy bin of 10–11 keV. Both curves are divided by the maximum value for comparison. Vis_FwdFit (blue) fits a Gaussian distribution to the X-ray visibilities, and although the real X-ray profile may deviate from a Gaussian form assumed by Vis_FwdFit (and the CLEAN PSF), the low Vis_FwdFit χ² values tell us a Gaussian is an adequate approximation for the study.