A method for cleaning a substrate is provided that includes applying a liquid medium to a surface of the substrate such that the liquid medium substantially covers a portion of the substrate that is being cleaned. The ammunition system includes an ammunition canister and feed system, the canister having a pair of brackets releasably coupled to a pair of receivers supported by a vertical mounting surface. The apparatus also has reference image updating means for determining when to generate a new reference image, for generating the new reference image, for replacing the current reference image with the new reference image, and for storing the new reference image as current reference image in the storage device. The flap member provides for control of airflow through the machine after proper clearances are established. Conventional helical scanning may still be undertaken. The scatter gather descriptor, context descriptor, and immediate data space are arranged contiguously in the descriptor ring to allow the descriptor ring to be read in a single direct memory access transfer or burst.