We present the first detailed investigations of the ablative acceleration of planar targets while simultaneously using high irradiance (10/sup 14/ W/cm/sup 2/), large focal diameters (1 mm) and long laser pulse duration (3 nsec). Included are measurements of target preheat, ablation pressures and uniformity achieved under these conditions. Targets were accelerated to high velocities with velocity profile uniformity approaching that required for high gain pellet implosions.