Modelling the Low‐Pressure N₂O₂ Plasma Afterglow to Determine the Kinetic Mechanisms Controlling the UV Emission Intensity and Its Spatial Distribution for Achieving an Efficient Sterilization Process

Abstract

The flowing afterglow of a N2O2 microwave discharge intended to provide intense and spatially uniform UV emission for an efficient inactivation of bacterial spores is modelled with a 3‐D hydrodynamic model leading to the spatial density distribution of the species in the reactor. The agreement of the calculated densities of the NO(A) and NO(B) UV emitting species with the corresponding measured emission intensities strongly supports the choice of the kinetic reactions retained in the model. In that respect, the specific contribution of N and O atoms to the spatial distribution of the NO(A) density (generating the NOγ system) in the late afterglow is, for the first time, brought into relief.magnified image

Sterilization/disinfection of medical devices using plasma: the flowing afterglow of the reduced-pressure N2-O2discharge as the inactivating medium

“…Figure 3a shows the density variation of N ions, is considered herein as the end of the early afterglow while the subsequent afterglow is referred to as the late afterglow. Figure 3b shows the time evolution of the (groundstate) densities of O and N atoms, indicating that these vary little with time up to 10 ms, their density starting to decrease significantly beyond 100 ms [12]. Figure 2 schematizes the situation where the distance x d from the plasma source to the chamber entrance is not long enough (corresponding to an elapsed time <10 ms in Fig.…”

“…3) to ensure that only late afterglow species are present throughout the chamber. The early afterglow species coming in into the chamber in this case are represented as a slightly divergent cylindrical beam that dies out within the chamber, as functions of the axial distance x from the chamber entrance and distance z from the discharge axis down the chamber [12]. The late afterglow dominates outside this beam flow.…”

O2 dissociation in Ar–O2 surface-wave microwave discharges

“…The calculations are conducted for this critical electron density, so that the species densities are obtained at the end of the plasma column, being thus the initial conditions of the afterglow. The latter is dominated by the gas phase chemical kinetics and surface pro-cesses [4,9,14,18]. The sustaining microwave field for the discharge plasma is self-consistently calculated.…”

“…Afterglow systems based on oxygen containing surface-wave microwave discharges meet several applications in the fields of biomedicine [1][2][3][4] and surface treatment [5,6], with further potential in areas such as nanotechnology [7][8][9]. In numerous applications the major role is played by the O-atoms, although most of the time a synergetic effect between the O-atoms and ions or UV photons is observed.…”

Influence of nitrogen impurities on the formation of active species in Ar-O2plasmas

“…Basically, the homogeneous electron Boltzmann equation is solved in the two-term expansion in spherical harmonics, coupled with a set of rate balance equations describing the creation and loss of the most important neutral and ionic species, including the molecu- [22,23]. Information related to the N 2 -Ar reactions can be found in [25][26][27], to the N 2 -O 2 kinetics in [28][29][30], and to the vibration kinetics and the calculation of the vibration levels in [31,32]. The system of equations is solved in stationary discharge conditions, considering an electron density corresponding to the critical density for surface-wave propagation, n e = 3.74 × 10 11 cm −3 [22], describing approximately the conditions at the end of the plasma column.…”