CO2 monitoring by optical emission spectroscopy and mass spectrometry for CO2 plasmas

Carbon dioxide is a critical gas for many industrial and scientific applications. Different metrologies can be employed to measure the CO2 concentration in such systems. In this work quadrupole mass spectrometry and optical emission spectroscopy methods are compared. The QMS method was implemented by an SRS Universal Gas Analyzer and the OES method through a Gencoa OPTIX remote spectrometer. These are attached to the Carbon Dioxide Optical Measurement Apparatus which attempts to recreate industrial CO2 systems in a lab environment using an inductively coupled plasma discharge. The CDOMA system operates at a pressure of approximately 1 Torr with a gas flow of 140 sccm containing helium, nitrogen, and carbon dioxide. Optical measurement monitored selected peaks from the CO Angstrom and N2 second positive spectroscopic systems. The measurement of CO from the OES and CO2 from the QMS methods are compared as a measurement of net CO2 dissociation rates, a common metric for CO2 containing systems. In addition, the electron energy distribution function of the ICP plasma was measured with Langmuir probe. These results showed a bi-Maxwellian temperature distribution but may require a more rigorous study to confirm. The probe results were connected to a simplified 1-dimensional plug flow reactor model using Cantera. The model, using probe results as inputs, yielded similar results to experiments, but will require further development before it can be used as a predictor for the system. The experimental results showed around 90% CO2 dissociation, with an energy efficiency of 5%, which is comparable to other plasma discharges in literature. Results from the experimental setup showed the QMS method required a specific normalization such that data from different experiments could be compared. Whereas the OES data required calibration before the results could be readily measured. After normalization and calibration, both methods are compared. There is evidence to suggest that QMS is much more sensitive to environmental conditions, whereas the OES data was more sensitive to changes in CO concentration under higher power operation. It is suggested that this is due to the differential pumping of the RGA leading to changes from gas temperature and concentrations, whereas the OPTIX has no or little differential pumping. Overall, the methods are very comparable, and implementation of either or both metrologies would need to be studied further on the system of interest. The OES method is advantageous for recirculating gas systems as it is noninvasive and does not require direct gas sampling or differential pumping. This would be of particular interest for multi-pass CO2 conversion systems or CO/CO2 lasers.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Nuclear, Plasma, Radiolgc Engr

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Herschberg, Andrew Clark

Contributors dc:contributor

• Ruzic, David N
• Qerimi, Dren

• CO2 Plasma
• Optical Emission Spectroscopy
• Mass Spectrometry
• Plasma Diagnostics
• CO2 Plasma Model
• Langmuir Probe

Statement dc:rights

• Copyright 2025 Andrew Herschberg

Language dc:language

en

Handle dc:identifier

https://hdl.handle.net/2142/132589

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/132589