A gas inlet system for a wafer processing reactor includes a tubular gas manifold conduit adapted to be connected to a gas inlet port of the wafer processing reactor; and gas feeds including a first feed for feeding a first gas into the tubular gas manifold conduit and a second feed for feeding a second gas into the tubular gas manifold conduit. Each feed has two or more injection ports connected to the tubular gas manifold conduit at a first axial position of the tubular gas manifold conduit, and the injection ports of each of the gas feeds are evenly distributed along a circumference of the tubular gas manifold conduit at the first axial position.