A measurement system to measure a concentration of neutral gas species above a substrate includes a substrate support located in a chamber to support a substrate. A plasma source generates plasma in the chamber above the substrate. The plasma generates metastable species having higher ionization energy than a neutral gas species. The metastable species excite the neutral gas species located above the substrate. An optical emission spectrometer (OES) sensor measures spectra from a location above the substrate while the plasma is generated by the plasma source. A controller is configured to determine a concentration of the neutral gas species in a region above the substrate based on the measured spectra and to selectively process the substrate based on the concentration.

A measurement system to measure a concentration of neutral gas species above a substrate includes a substrate support located in a chamber to support a substrate. A plasma source generates plasma in the chamber above the substrate. The plasma generates metastable species having higher ionization energy than a neutral gas species. The metastable species excite the neutral gas species located above the substrate. An optical emission spectrometer (OES) sensor measures spectra from a location above the substrate while the plasma is generated by the plasma source. A controller is configured to determine a concentration of the neutral gas species in a region above the substrate based on the measured spectra and to selectively process the substrate based on the concentration.

A gauge that is configured to detect a time at which radiation enters the gauge. The gauge may include a member that is configured to transition from a first state to a second state upon receipt of the incoming radiation, and may include a light probe that is configured to detect when the member transitions to the second state. The gauge may provide for determining a time of arrival of the radiation at another gauge. For example, the gauge may correlate the time of arrival at the gauge with the another gauge, thereby providing for correlating a response time of a test specimen with actual exposure time of the test specimen to radiation (e.g., an ion beam).

A gauge that is configured to detect a time at which radiation enters the gauge. The gauge may include a member that is configured to transition from a first state to a second state upon receipt of the incoming radiation, and may include a light probe that is configured to detect when the member transitions to the second state. The gauge may provide for determining a time of arrival of the radiation at another gauge. For example, the gauge may correlate the time of arrival at the gauge with the another gauge, thereby providing for correlating a response time of a test specimen with actual exposure time of the test specimen to radiation (e.g., an ion beam).