Effect of pulse width and repetition frequency on the uniformity and accumulation effect of atmospheric-pressure nanosecond pulsed DBD

Abstract Nanosecond (ns) pulse excitation is considered a promising method for enhancing atmospheric-pressure plasma chemical reactivity due to its good controllability and uniformity. Pulse width and pulse repetition frequency (PRF) are important parameters of the pulsed voltage, which significantly influence the discharge processes both within a single discharge cycle and between adjacent discharges. In this paper, the uniformity and accumulation effect of discharges with different pulse widths and PRFs are investigated by experimental and numerical methods. To reveal the variation of voltage on gap ( U g ), discharge current ( I g ), electron density ( n e ), and accumulated charges on the dielectric barrier, the measured voltage-current waveforms were separated. The results show that as pulse width increases, on the rising edge, U g and I g change little, but on the falling edge, increase significantly due to the dissipation of space-active species. Higher U g and a higher reduced electric field ( E / n ) on the falling edge lead to more electron avalanches, which enhance discharge uniformity ( n e ) and electron temperature ( T e ). With a further increase in pulse width, U g on the falling edge increases, leading to distortion of the space electric field and a reduction in uniformity. An increase in PRF causes the increase of space residual active species, which decrease U g and I g and the discharge uniformity. The spatiotemporal evolutions of discharge are recorded by intensified charge-coupled device (ICCD) camera and one-dimensional (1D) fluid simulation is also performed to explain the roles of electric field and charge accumulation.