Wave propagation and noncollisional heating in neutral loop and helicon discharges

Journal Article · Tue Feb 15 04:00:00 EST 2011 · Physics of Plasmas

DOI:https://doi.org/10.1063/1.3551758· OSTI ID:21535145

Celik, Y; Crintea, D L; Luggenhoelscher, D; Czarnetzki, U ^[1]; Ishijima, T ^[2]; Sugai, H ^[3]

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1. Institute for Plasma and Atomic Physics, Ruhr University Bochum, Universitaetsstrasse 150, 44780 Bochum (Germany)
2. Plasma Nanotechnology Research Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603 (Japan)
3. Department of Electronics and Information Engineering, Chubu University, 1200 Matsumoto-cho, Kasugai 487-8501 (Japan)

Heating mechanisms in two types of magnetized low pressure rf (13.56 MHz) discharges are investigated: a helicon discharge and a neutral loop discharge. Radial B-dot probe measurements demonstrate that the neutral loop discharge is sustained by helicon waves as well. Axial B-dot probe measurements reveal standing wave and beat patterns depending on the dc magnetic field strength and plasma density. In modes showing a strong wave damping, the plasma refractive index attains values around 100, leading to electron-wave interactions. In strongly damped modes, the radial plasma density profiles are mainly determined by power absorption of the propagating helicon wave, whereas in weakly damped modes, inductive coupling dominates. Furthermore, an azimuthal diamagnetic drift is identified. Measurements of the helicon wave phase demonstrate that initial plane wave fronts are bent during their axial propagation due to the inhomogeneous density profile. A developed analytical standing wave model including Landau damping reproduces very well the damping of the axial helicon wave field. This comparison underlines the theory whereupon Landau damping of electrons traveling along the field lines at speeds close to the helicon phase velocity is the main damping mechanism in both discharges.

• OSTI ID: 21535145
• Journal Information: Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 2 Vol. 18; ISSN PHPAEN; ISSN 1070-664X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
DAMPING
ELECTRIC DISCHARGES
ELECTROMAGNETIC RADIATION
HELICON WAVES
HIGH-FREQUENCY DISCHARGES
LANDAU DAMPING
PHASE VELOCITY
PLASMA DENSITY
PLASMA PRESSURE
RADIATIONS
STANDING WAVES
VELOCITY
WAVE PROPAGATION