Methods for processing events occurring in a process chamber are provided. In one method, an operation includes carrying gas and receiving an optical signal from the process chamber to an analysis tool that operates in response to the optical signal having a signal-to-noise ratio (SNR) for process analysis. And, dividing the carried gas and optical signal into a plurality of separate gas and optical signals between the process chamber and the analysis tool. The dividing is configured through separate apertures so that the apertures collectively maintain the SNR of the optical signal received at the tool. Methods provide a septum in a second bore dividing the second bore into apertures configured to reduce etching of and deposition on the optical access window and to maintain the desired SNR at the diagnostic end point.