circumpetally that is radially into ablation opening 5 and away from the substrate 15 in ablation opening riser tube 8 because the sweeping gas now carrying particulate matter and gaseous exhaust enters into the lower partial pressure of debris collection chamber 1 the flow follows the walls of ablation riser tube 8 leaving little interference with the ablation radiation beam 6 which follows the axis at a central position the sweeping gas with its gaseous and particulate products collectively u201c waste u201d is sucked primarily into debris exhaust chamber 1 and to a lesser extent bypasses chamber 1 and passes directly into debris exhaust chamber 2 sweeping gas entry chamber 3 is connected to an inert gas inlet 16 supplying inert gas at high partial pressure the sweeping gas is typically one or a mixture of air nitrogen and helium helium is preferred in our embodiment the sweeping gas already reduced to a relatively high partial pressure is fed through multiple atmospheric pressure metering holes 4 the sweeping gas forms an enveloping gas virtual fence around the process region ablation site 7 over the substrate 15 the combination of inert gas debris particles 18 and air are all removed circumferentially out through the ablation opening 5 between chamber 2 and extension of chamber 1 and through the chamber 2 this keeps the light path clear from any debris under uniform gas.