On peak current in atmospheric pulse-modulated microwave discharges by the PIC-MCC model

Pulse modulation provides a new way to tailor the electron density, electron energy and gas temperature in atmospheric radio-frequency (rf) discharges. In this paper, by increasing the rf frequency to several hundreds of MHz, or even much higher to the range of GHz, a very strong peak current in the first period (PCFP) with much larger electron energy can be formed during the power-on phase, which is not observed in the common pulse modulation discharges at a rf frequency of 13.56 MHz. The PIC-MCC model is explored to unveil the generation mechanism of PCFP, and based on the simulation data a larger voltage increasing rate over a quarter of a period and the distribution of electron density just before the power-on phase are believed to play key roles; the PCFP is usually produced in the microplasma regime driven by the pulsed power supply. The effects of duty cycle and pulse modulation frequency on the evolution of PCFP are also discussed from the computational data. Therefore, the duty cycle and pulse modulation frequency can be used to optimize the generation of PCFP and high-energy electrons.