Analysis of microwave propagation in a time-varying plasma slab with particle-in-cell simulations

Abstract

Continuous microwave propagation through a time-varying plasma and frequency up-conversion has been demonstrated by particle-in-cell (PIC) simulation. In principle, it is possible to transform a 2.45 GHz source radiation to an arbitrary larger frequency radiation. The energy conversion is also obtained by the theoretical analysis and has been testified by PIC simulation. The source wave was propagating in a parallel plate waveguide locally filled with the ionized gas. In this paper we would discuss the effects of the rise time, the plasma length, the switching time and the collision frequency on the energy conversion, and the methods to improve the upshift wave energy are proposed. We also put forward the new concept of the critical values of the rise time and the source wave amplitude to provide a theoretical basis for the selection of parameters in the experiments.

Microwave frequency downshift in the time-varying collision plasma

“…So it finds a balance between these two factors. Under this precondition, the plasma thickness d and the rise time T r have no effect on the EM wave frequency [21,22]. The collision frequency self-consistent process in the three models can refer to the MAGIC manual, in which the drag, scattering and straggling are modeled according to the following equations:…”

“…The reason for the two peaks is the influence of the ionization rise time. In our previous work, the effect of the ionization rise time on the frequency conversion is obtained [22]. Suppose that the ionization process is too slow, a part of the incident wave propagates out the time-varying plasma during the ionization rise time, without undergoing a complete time-varying ionization process.…”

“…As for the interaction between EM waves and the timevarying plasma, the frequency upshift is widely known. For example, a more perfect theoretical analysis is proposed by Kalluri [19,20], the particle-in-cell (PIC) simulation verification is demonstrated by Chen [21,22], and several proofof-principle experiments are reported by Kuo [23] and Nishida [24,25]. Nevertheless, the frequency downshift of EM waves in the time-varying collision plasma is disregarded.…”