In Plasma Source Ion Implantation (PSII), a target to be implanted is immersed in a weakly ionized plasma and pulsed to a high negative voltage. Ions in the plasma are accelerated toward the target and implanted in its surface, thereby modifying the properties of the surface. Experimental results reported in the literature have generally been for small targets. We present here the design of a large-scale PSII experiment being assembled Los Alamos National Laboratory, in which we plan to implant targets with surface areas exceeding 1 m2 to doses of up to 5 × 1017 cm−2. In presenting this design, we use Monte Carlo and particle-in-cell simulations to examine sheath expansion, implant current and dose, secondary electron emission, target sputtering, implant depth, and x-ray emission resulting from secondary electrons hitting the vacuum chamber wall.