Curling probe measurement of a large-volume pulsed plasma with surface magnetic confinement. (24th October 2016)

• Record Type: Journal Article
• Authors: Pandey, A; Tashiro, H; Sakakibara, W; Nakamura, K; Sugai, H
• Is Part Of: Plasma sources science & technology. Volume 25:Number 6(2016:Dec.)
• Publication Date: 2016-10-24
• Subjects: curling probe -- electron density -- pulse discharge -- surface magnetic confinement -- cathode sheath; Plasma (Ionized gases) -- Periodicals; 530.44
• DOI: 10.1088/0963-0252/25/6/065013
• Languages: English
• ISSNs: 0963-0252

Abstract

Abstract: A curling probe (CP) based on microwave resonance is applied to the measurement of electron density in a pulsed DC glow discharge under surface magnetic confinement (SMC) provided by a number of permanent magnets on a chamber wall. Owing to the SMC effects, a 1 m scale large-volume plasma is generated by a relatively low voltage (~1 kV) at low pressure (~1 Pa) in various gases (Ar, CH4, and C2 H2 ). Temporal variation of the electron density is measured for pulse frequency f = 0.5–25 kHz for various discharge-on times ( T ON ) with a high resolution time (~0.2 µ s), using the on-point mode. In general, the electron density starts to increase at time t = 0 after turn-on of the discharge voltage, reaches peak density at t = T ON, and then decreases after turn-off. The peak electron density is observed to increase with the pulse frequency f for constant T ON owing to the residual plasma. This dependence is successfully formulated using a semi-empirical model. The spatio-temporal evolution of the cathode sheath in the pulsed discharge is revealed by a 1 m long movable CP. The measured thickness of the high-voltage cathode fall in a steady state coincides with the value of the so-called Child–Langmuir sheath.