Study of NO production and UV emission over the E-H mode transition in a double inductively coupled plasma device

Inductively coupled plasma devices (ICP) are known for the production of higher electron densities than comparable capacitively coupled plasma devices (CCP). These increased electron densities promote the production of excited and reactive species, as well as increased photon emission, which are crucial to multiple technological applications.

In this work a low-pressure double inductively coupled plasma (DICP) is ignited in gas mixtures of nitrogen and oxygen, with the goal of producing nitric oxide molecules and UV radiation. The plasma is studied with respect to gas temperature and photon emission rates by optical emission spectroscopy (OES), absolute densities of nitric oxide by laser-induced fluorescence (LIF), as well as electron density and electron temperature by multipole resonance probe (MRP). A collisional radiative model is then benchmarked against the measured UV photon emission rates.

The results reveal a sensitive dynamic between the densities of nitric oxide, the excitation of this species driven by electron impact and nitrogen metastables, and the resulting UV photon emission rate. The nitric oxide density is shown to increase with power while the discharge remains in E-mode, and decreases significantly with the transition to H-mode. The UV photon emission rate, however, due to increasing electron densities in H-mode, is shown to increase continuously towards higher powers. The chemical kinetics model is able to reflect this dynamic accurately, qualitatively and quantitatively.