Parametric analysis of mode coupling and liner energy deposition properties of helicon and Trivelpiece-Gould waves in helicon plasma

Abstract

Based on the finite temperature plasma dielectric tensor model which contains the particle thermal effect, by numerically solving the eigenmode dispersion relation of electromagnetic waves propagating in radially uniform and magnetized warm plasma column which is surrounded by conducting boundary, the mode coupling characteristic and liner damping mechanism induced wave power deposition properties of helicon and Trivelpiece-Gould (TG) waves are parametrically analyzed. The detailed investigations show as follows. Under typical helicon plasma parameter conditions, i.e. wave frequency <i>ω</i>/(2π) = 13.56 MHz, ion temperature is much smaller than electron temperature, for the helicon wave, there exist a cut-off magnetic field <i>B</i><sub>0,H,cutoff</sub> and a cut-off plasma density <i>n</i><sub>0,H,cutoff</sub>, for which under the conditions of <i>B</i><sub>0</sub> > <i>B</i><sub>0,H,cutoff</sub> or <i>n</i><sub>0</sub> < <i>n</i><sub>0,H,cutoff</sub>, the helicon wave becomes an evanescent wave. When the magnetic field intensity changes from 48.4 to 484 G, i.e., <i>ω</i>/<i>ω</i><sub>ce</sub> ranges from 0.01 to 0.1, for the power deposition intensity, Landau damping of TG wave dominates for the <i>m</i> = 0 mode, meanwhile, for the <i>m</i> = 1 mode, which wave, i.e. helicon wave or TG wave, plays a major role in power deposition mainly depends on the magnitude of the magnetic field. On the other hand, for a given magnetic field <i>B</i><sub>0</sub> = 100 G, when <i>ω</i><sub>pe</sub>/<i>ω</i><sub>ce</sub> changes from 3 to 100, for both the <i>m</i> = 0 mode and the <i>m</i> = 1 mode, the power deposition induced by Landau damping of TG wave plays a major role, further, one may notice that the power deposition of TG wave decreases while the power deposition of the helicon wave increases as plasma density increases. Finally, for both the <i>m</i> = 0 mode and the <i>m</i> = 1 mode, the power deposition due to the Landau damping plays a dominant role. All these conclusions provide us with some useful clues to better understanding the high ionization mechanism of helicon wave discharges.

Influence of temperature and pressure gradient on power deposition and field pattern in High Magnetic field Helicon eXperiment

“…Equations ( 1) and ( 2) can be converted by Fourier change into the following six equations to solve the various components in cold plasma [24][25][26] :…”

Influence of magnetic field on power deposition in high magnetic field helicon experiment

“…HELIC code is composed of Maxwell's equations for a radially non-uniform plasma with the standard cold-plasma dielectric elements S, D, P (= ε xx , iε xy , ε zz ). These equations can be manipulated to give the following set of coupled differential equations for the Fourier transformed variables: [19][20][21]…”

“…( 1)-( 4) are programmed to solve, and four basic functions are generated, namely b r , b z , e r , and e z . In the cylindrical coordinate system, if the plasma is uniform, the basis function b 1,2;z (r) is the Bessel function J m (T 1,2 r), where [21] ST 4 1…”

Simulation of a helicon plasma source in a magnetoplasma rocket engine

“…It is worth noting that the electron density is basically the same when the mode converts, even at different input currents. The discharge mode first converts when the density is about 2×10 16 m −3 and it converts for the second time when the density is about (2-3)×10 18 m −3 . If the background magnetic field of the helicon discharge remains constant, the plasma density at the MCS remains unchanged.…”

“…There are two wave branches in the solution of the helicon dispersion relation [11]: one is the helicon wave and the other is called the Trivelpiece-Gould wave (TG wave) [12]. Research showed that the power absorption can be more appropriately explained by the strong damping of the TG wave [13][14][15][16]. Another unique phenomenon in helicon discharges is that the plasma density jumps at a certain power, accompanied by a change of discharge mode [17,18].…”