We have developed a compact laser system capable of amplifying nanosecond-scale pulses form a few picojoules to 20J. The system has a 40-mm clear aperture and a 37-mm working aperture for high-energy output. We measured less than 1 wave phase distortion over full 37-mm aperture for a pulse with 18-J output energy at a shot repetition rate of one shot every 10 min. In experiments with a 30-mm diam beam, a flat-top spatial profile with 4 percent rms over the entire beam diameter was demonstrated for a 1-ns pulse with 20_j output energy. The amplifier has a net gain up to 10<SUP>13</SUP> and fits easily on a 5-ft X 14-ft optical table.