A 200-kV, 200-mA deuterium ion accelerator has been developed to simulate the operation of an intense neutron source for use in cancer therapy. The thin-film ScD2 target for the neutron source is supported on a water-cooled copper substrate designed to dissipate 40 MW/m2 at a surface temperature of 450 °C. This paper describes the theoretical and experimental analysis of the target and the postmortem analysis of a target after 140 h of operation at power densities exceeding 40 MW/m2. Cooling channel erosion due to nucleate boiling of the cooling water was shown to be the life-limiting feature of the target design.