We present images of the source of extreme ultraviolet (XUV) harmonic emission at a wavelength of 220 Å from the interaction of a 20 TW, 1.053 &mgr;m Nd:glass laser beam focused to intensities up to 4×1018W cm−2onto a solid target. From these measurements we determine an upper limit to the source size and brightness of the harmonic emission to show its efficacy as a novel source of short-pulse, coherent XUV radiation. We also demonstrate the empirical scaling of the harmonic generation efficiency with irradiance up to 1019W &mgr;m2 cm−2, and extrapolate to estimate the possible source brightness at higher irradiances. These source brightnesses are compared to those available from an x-ray laser system. ©1997 American Institute of Physics.