LAUSR

We investigate the influence of the surrounding gas on the behaviour of guided ionization waves by measuring the electric field, propagation dynamics and emission spectra of a kHz operated helium plasma jet in surrounding gases such as nitrogen, oxygen and dry air. The electric field measurements performed using an electro-optic BSO crystal and the amount of deposited charge on the dielectric surface were calculated. These measurements showed a unique growth profile of the surface discharge in each of these surrounding gases after the guided ionization waves reaches the dielectric surface. The branching of surface discharges is observed when the nitrogen was used as the surrounding gas. The surface discharge profile in dry air and oxygen was diffused without any branching and it is wider in oxygen. The speed of growth of the discharge on the surface also decreases in nitrogen compared to dry air and oxygen. The measurements of propagation dynamics showed that the velocity of guided ionization waves is higher in oxygen containing gases. The result of this study showed that the presence of oxygen in the surrounding gas has a significant effect on guided ionization waves. These effects are mainly due to the photoionization of oxygen in the surrounding gas and also the electron detachment from the anions formed from oxygen.