Evidence for electron energization accompanying spontaneous formation of ion acceleration regions in expanding plasmas

Aguirre, Evan; Bodin, Rikard; Yin, Neng; Good, T. N.; Scime, Earl

doi:10.1063/5.0025523

Cited by 15 publications

(11 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This is basically consistent with the previous reports [e.g. 35,67,68], indicating a change from edge heating to central heating through the radial electron temperature and electric field profiles as well as power deposition, accompanied by the transition to BC mode. According to this mechanism, the transition from NW to BC mode in a helicon plasma looks like a transition from general helicon waves propagation into the anti-resonance region of TG waves with enhanced volume absorption by helicon waves, although the transition conditions are needed to be clarified.…”

supporting

confidence: 93%

Comparison of heating mechanisms of argon helicon plasma in different wave modes with and without blue core

Cui

Zhang²,

Yuan³

et al. 2022

Plasma Sci. Technol.

View full text Add to dashboard Cite

In this work, we investigated the discharge characteristics and heating mechanisms of argon helicon plasma in different wave coupled modes with and without blue core. Spatially resolved spectroscopy and emission intensity of argon atom and ion lines were measured via local optical emission spectroscopy (LOES), and electron density was measured experimentally by an RF-compensated Langmuir probe (LP). The relation between the emission intensity and the electron density was obtained and the wavenumbers of helicon and TG waves were calculated by solving the dispersion relation in wave modes. The results show that at least two distinct wave coupled modes appear in argon helicon plasma at increasing RF power, i.e., blue core (or BC) mode with a significant bright core of blue lights and a normal wave (NW) mode without blue core. The emission intensity of atom line 750.5 nm (IArI750.5 nm) is related to the electron density and tends to be saturated in wave coupled modes due to the neutral depletion, while the intensity of ion line 480.6 nm (IArII480.6 nm) is a function of the electron density and temperature, and increases dramatically as the RF power is increased. Theoretical analysis shows that TG waves are strongly damped at the plasma edge in NW and/or BC modes, while helicon waves are the dominant mechanism of power deposition or central heating of electrons in both modes. The formation of BC column mainly depends on the enhanced central electron heating by helicon waves rather than TG waves since the excitation of TG waves would be suppressed in this special anti-resonance region.

show abstract

supporting

confidence: 93%

Comparison of heating mechanisms of argon helicon plasma in different wave modes with and without blue core

Cui

Zhang²,

Yuan³

et al. 2022

Plasma Sci. Technol.

View full text Add to dashboard Cite

show abstract

“…That helped to reduce the collision frequency to maintain high T e at the edge. This phenomenon meant that the central heating by the helicon wave was weakened, while the edge heating in the skin layer was strengthened by stochastic heating [27,33,68] or TG wave [52,69], and this enhancement also meant the change of power dissipation mechanism of the waves with the increase of pressure. It is also shown that the intermediate pressure case exhibits the lowest value rather than the highest pressure in figure 9.…”

Section: ( ) ( )mentioning

confidence: 99%

Effect of neutral pressure on the blue core in Ar helicon plasma under an inhomogeneous magnetic field

Wang

Liu²,

Sun³

et al. 2023

Plasma Sci. Technol.

View full text Add to dashboard Cite

The effect of neutral pressure on blue core in Ar helicon plasma under inhomogeneous magnetic field was investigated in this work. The neutral pressure was set to 0.08 Pa, 0.36 Pa and 0.68 Pa. Nikon camera, intensifies charge coupled device (ICCD), optical emission spectrometer (OES), and Langmuir probe were used to diagnose the blue core in helicon plasma. Helicon plasma discharges experienced density jumps from E-, H- to W-mode before power just rose to 200 W. The plasma density increased and maintained the central peak with the increase of neutral pressure. However, the brightness of the blue core gradually decreased. It demonstrated that the relative intensity of Ar II spectral lines and the ionization ratio in the central area were reduced. Radial electron temperature profiles were flattened and became hollow as neutral pressure increased. It demonstrated that increasing the neutral pressure weakened the central heating efficiency dominated by helicon wave and strengthened the edge heating efficiency governed by the TG wave and skin effect. Therefore, the present experiment successfully reveals how the neutral pressure affects the heating mechanism of helicon plasma in inhomogeneous magnetic field.

show abstract

“…The RF power is mainly absorbed by electrons in the inductively coupled or helicon modes [1]. Note that the neutral energy is negligibly small because the neutral temperature is roughly 300 K, while the measured ion and electron temperatures are 0.1-1 eV [24] and 1-20 eV [25,26], respectively. In addition, the magnetostatic field produced by the solenoid supplies no energy to the plasma.…”

Section: Introductionmentioning

confidence: 97%

Vector Resolved Energy Fluxes and Collisional Energy Losses in Magnetic Nozzle Radiofrequency Plasma Thrusters

2021

View full text Add to dashboard Cite

Energy losses in a magnetic nozzle radiofrequency plasma thruster are investigated to improve the thruster efficiency and are calculated from particle energy losses in fully kinetic simulations. The simulations calculate particle energy fluxes with a vector resolution including the plasma energy lost to the dielectric wall, the plasma beam energy, and the divergent plasma energy in addition to collisional energy losses. As a result, distributions of energy losses in the thruster and the ratios of the energy losses to the input power are obtained. The simulation results show that the plasma energy lost to the dielectric is dramatically suppressed by increasing the magnetic field strength, and the ion beam energy increases instead. In addition, the divergent ion energy and collisional energy losses account for approximately 4%–12% and 30%–40%, respectively, regardless of the magnetic field strength.

show abstract

Evidence for electron energization accompanying spontaneous formation of ion acceleration regions in expanding plasmas

Cited by 15 publications

References 43 publications

Comparison of heating mechanisms of argon helicon plasma in different wave modes with and without blue core

Comparison of heating mechanisms of argon helicon plasma in different wave modes with and without blue core

Effect of neutral pressure on the blue core in Ar helicon plasma under an inhomogeneous magnetic field

Vector Resolved Energy Fluxes and Collisional Energy Losses in Magnetic Nozzle Radiofrequency Plasma Thrusters

Contact Info

Product

Resources

About