Nanosecond-pulsed dielectric barrier discharges in Kr/Cl₂for production of ultraviolet radiation

Abstract

In this paper, we present a study of nanosecond-pulsed, coaxial dielectric barrier discharges for generation of UV radiation in Kr/Cl 2 mixtures with total pressures of 25 and 50 mbar. This study is based on an ensemble of experimental and modeling results and aims to identify the dominant physical mechanisms leading to the production of KrCl * (B state). The emission band of KrCl * is peaked at 222 nm, which is in the wavelength range of interest for applications in microbial decontamination. We find that for the same energy per pulse deposited in the discharge, more UV radiation is emitted at higher pressures where relatively more of the energy deposited in the gas goes into heating the electrons, with less going to heating the ions in the sheath. The Cl 2 partial pressure significantly affects the KrCl * time-averaged, spatial profiles, leading to different optimal conditions for average and for peak UV power densities. Model results show that the highest KrCl * number density occurs near the walls and is associated with the development of cathode sheaths during the voltage pulse.

Atmospheric pressure dual RF-LF frequency discharge: influence of LF voltage amplitude on the RF discharge behavior

“…The discharge is simulated using a 1D self-consistent fluid model, based on a general 2D plasma code previously used for other discharges and described in [34] [35], which was adapted to the DBD geometry in 1D Cartesian space. This model solves the electron, ion and metastable continuity and momentum transfer equations coupled to Poisson's equation.…”

The effect of the pulse repetition rate on the fast ionization wave discharge

“…Firstly, with a given electric field and pressure of helium, a 0D steady state Boltzmann equation solver (freeware Bolsig+ [18]) is used to obtain the EEDF, which is used to calculate electron transport parameters and rate coefficients for electron collisional processes. Secondly, using these parameters, a fluid model with the local energy approximation is used to obtain the distribution and evolution of the axial electric field, as well as the electron density (n e ), ion density (n i ), and mean electron energy ( ε e ) [19,20]. Thirdly, using EEDF, electron density, and ion density obtained above, a time-dependent collisional-radiative model for helium is used to obtain the temporal evolution of the population of excited states [21][22][23].…”

“…In this work, a 0D steady state Boltzmann equation solver (freeware Bolsig+ [18]) is used to solve the Boltzmann equation and to obtain the EEDF with a given reduced electric field in helium. A similar method has been adopted in a nanosecond pulsed dielectric barrier discharge in Kr/Cl 2 mixture with a pressure of ~25-75 mbar in [19]. Under the steady state assumption, the ∂f/∂t term in equation (3.1) is set to zero.…”

“…Therefore, in this fluid model, the mean electron energy ε e is used instead of the electron temperature and the effect of the EEDF is represented by the electron transport parameters (µ e , D e , µ eε , and D eε ) and rate coefficients for electron collisional processes (R iz , R el , and R inel ). We assume that there is a one-to-one correspondence between ε e and the EEDF, as done in [1,19]. Therefore, the dependence of these parameters on ε e is tabulated, as illustrated in figure 3.…”

Optimizing drive parameters of a nanosecond, repetitively pulsed microdischarge high power 121.6 nm source

“…Such a device holds a unique status for VUV photolithography sources as 121.6 nm occupies essentially the lowest usable wavelength for optics systems, due to the fact that the best VUV optics (LiF and MgF 2 ) will not transmit light below wavelengths of ∼115 nm. Additional applications of UV/VUV sources include the direct photo-ionization of gases [1], energy efficient triggering of undervoltaged spark gaps [1], and sanitation and purification [2,3]. Other applications may be found in high pulse repetition rate triggering of photoconductive solid-state switches, possibly replacing other pulsed light sources at longer wavelengths [4].…”