Microwave electron cyclotron resonance (ECR) plasma reactors have demonstrated excellent potential in etching and thin-film deposition applications for semiconductor processing. The further development of ECR plasma processing technology requires that the operation of the reactors be better understood and characterized. This Research Initiation Award project is investigating ECR plasmas through numerical modeling techniques and diagnostic techniques. The objectives of this study are to investigate the spatial uniformity species and electrons. The significance of these studies is that they will produce a predictive model of the reactors and improve the plasma reactors by directing future applications. The ECR plasma reactor studied consist of a single mode microwave cavity that supplies the energy to a plasma production region which has a multipolar static magnetic field. The experimental diagnostics data to be utilized to verify and refine the numerical models includes data collected using laser induced fluorescence spectroscopy, coherent anti-Stokes Raman spectroscopy, emission spectroscopy, actinometry, electric field probing, magnetic field probing, ion energy analysis, and Langmuir probe measurements.