Static elimination performance of a corona ionizer in nitrogen-based electronegative gases

Static neutralization characteristics of an AC corona ionizer in oxygen-free gas atmospheres such as mixed N₂-SF₆ and N₂-CF₃I gases have been explored and compared with those in ambient air and pure nitrogen. In pure nitrogen, the negative emitter current is much larger than the positive one due to difference in the mobility between negative (electrons) and positive (ions) carriers; hence the product final voltage VPF deviates to -2 kV. With introduction of CF₃I up to 0.01%, however, VPF reduces to around 0 V, while it happens at as high as 10% in O₂. Therefore it is found that the amount of CF₃I needed to improve the ion balance is three orders of magnitude smaller than that of O₂, due to higher electron affinity of a CF₃I molecule.