Effects of magnetic field on electron power absorption in helicon fluid simulation

Abstract

In this study, a code, named Peking University Helicon Discharge (PHD), which can simulate helicon discharge processes under both a background magnetic field greater than 500 G and a pressure less than 1 Pa, is developed. In the code, two fluid equations are used. The PHD simulations led to two important findings: (1) the temporal evolution of plasma density with the background magnetic field exhibits a second rapid increase (termed as the second density jump), similar to the transition of modes in helicon plasmas; (2) in the presence of a magnetic field, the peak positions of electron power absorption appeared near the central axis, unlike in the case of no magnetic field. These results may lead to an enhanced understanding of the discharge mechanism.

Relationship of mode transitions and standing waves in helicon plasmas

“…For the W mode discharges, it is found that the plasma density undergoes the second and/or even multiple jumps over time, as shown in figure 4; the same as the results in [32].…”

“…A single-fluid model of equations (1)-( 5) is applied, with basic discharge processes, such as ionizations, transports, and power depositions. The electromagnetic waves in vacuum and plasma areas can be described by Maxwell's equations (1) and (2) and the generalized Ohm's law equation (3) [1,32]. where J , a J p and B 0 are current densities of the antenna and the plasma, and the background magnetic field, respectively.…”

“…The ionization term = S k n n i n e is only for the ground state atom ionization and H i is the first ionization energy. The calculation of the ambipolar diffusion coefficients D a and Da and other parameters can be found in [32,33]. The boundary conditions on the plasma-wall interface are…”

“…Although many experiments have found density jumps [13,26,30,31], direct simulation results are still lacking. The Peking University Helicon Discharge (PHD) code [32] has been developed to study the mechanism of helicon discharges. It is found in this work that the large-amplitude SHWs formed during the discharge processes are responsible for the mode transitions.…”

First Helicon Plasma Physics and Applications Workshop

“…Mingyang Wu introduced a numerical study on the mode transition and discharge process of helicon plasma [38]. Simulations are conducted through a recently developed code, i.e., Peking university helicon discharge (PHD).…”