OES Diagnostics of Pre-Breakdown Light Emission in CoplanarAPGD in Helium

Phase resolved photon counting was applied to record low-resolved optical spectra of pre-breakdown light emitted in coplanar barrier discharge in helium. Light emissions from species as OH∗, N2+∗, He∗ as well as thermoluminescence of Al2O3 ceramics were observed during the whole voltage period. Moreover, a light with continuum spectrum was observed shortly before the discharge breakdown. Assuming neutral bremsstrahlung as the origin of the continuum, electric field of 0.5-1 kV/cm was obtained in this discharge phase.