Ultraviolet (UV) emissions from a unipolar submicrosecond pulsed dielectric barrier discharge (DBD) in He-Air mixtures

The ultraviolet (UV) emission from a fast-pulsed dielectric barrier discharge (DBD) in a He-air gas mixture has been investigated for a wide range of operating conditions (discharge gap: 1 cm, pressure: 100 - 750 Torr, voltage: 2.5 - 8 kV, sawtooth pulse: decay time ∼ 10 ns, frequency: 1.5 - 23 kHz, He-air mixture with 3%-30% air). The short-pulse excitation scheme allows the release of the charges deposited on the dielectric surfaces. The discharge (∼10 ns) studied here is ignited only when a fast shortening pulse is applied to a previously charged electrode. The emphasis of the studies was on the UV emissions from NO, OH, N₂, and N₂⁺ between 200 nm and 400 nm and their dependence on the discharge operating parameters. It was found that the main factor that determines the spectral distribution is the amount of air admixed to the He. Because of the importance of UV emissions around 250 nm in sterilization and biological applications, a calibrated photodiode was used for absolute intensity measurements of the NO γ-band system in the 200 - 280 nm range