Electron density modulation in an asymmetric bipolar pulsed dc magnetron discharge

Karkari, S. K.; Ellingboe, A. R.; Gaman, Cezar; Swindells, Ian; Bradley, James W.

doi:10.1063/1.2783980

Cited by 16 publications

(20 citation statements)

References 30 publications

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“…The basic construction of the hairpin probe is well described in the literature [4,5]. Essentially the probe comprises of a 50 Ω microwave coaxial line which has a small loop antenna at one end.…”

Section: Methodsmentioning

confidence: 99%

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Performance of a Floating Hairpin Probe in Strongly Magnetized Plasma

Karkari

Gogna

Boilson

et al. 2010

Contrib. Plasma Phys.

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This paper investigates the application of a floating hairpin probe for measuring the electron density in magnetized plasma. The magnetic field is systematically varied over a wide range (0.01 -0.15 T) and its influence on the probes resonance frequency is studied. The resonance frequency in plasma displays a negative shift when the electron cyclotron frequency becomes comparable with the resonance frequency in vacuum. A general formula for calculating the electron number density in magnetized plasma is hence obtained and the formula is experimentally validated. Comparison of the electron density using the improved formula shows very good agreement with the positive ion density measured by a planar Langmuir probe in the Kamaboko-III negative ion source.

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Section: Methodsmentioning

confidence: 99%

“…In recent years the hairpin probes has been successfully developed and applied to industrial plasmas [4][5][6]. The technique is based on measuring the plasma dielectric constant using a resonant structure resembling a hairpin [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Performance of a Floating Hairpin Probe in Strongly Magnetized Plasma

Karkari

Gogna

Boilson

et al. 2010

Contrib. Plasma Phys.

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“…17,21 The probe is made of tungsten wire of diameter equal to 0.38 mm. The wire is precisely cut and folded in the shape of a hairpin such that the pins are parallel to each other and separated by 3 mm.…”

Section: Resonance Hairpin Probe-assisted Laser Photodetachment Tementioning

confidence: 99%

“…17͒ and pulsed dc modes. 21 In this study, the electron density measurements are made with 10 ns time-resolution. This system is ideally suited for studying the transient behavior of the electron density following the photodetachment of negative ions.…”

Section: Introductionmentioning

confidence: 99%

Resonance hairpin and Langmuir probe-assisted laser photodetachment measurements of the negative ion density in a pulsed dc magnetron discharge

Bradley¹,

Dodd²,

You³

et al. 2011

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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The time-resolved negative oxygen ion density n− close to the center line in a reactive pulsed dc magnetron discharge (10 kHz and 50% duty cycle) has been determined for the first time using a combination of laser photodetachment and resonance hairpin probing. The discharge was operated at a power of 50 W in 70% argon and 30% oxygen gas mixtures at 1.3 Pa pressure. The results show that the O− density remains pretty constant during the driven phase of the discharge at values typically below 5×1014 m−3; however, in the off-time, the O− density grows reaching values several times those in the on-time. This leads to the negative ion fraction (or degree of electronegativity) α=n−/ne being higher in the off phase (maximum value α∼1) than in the on phase (α=0.05–0.3). The authors also see higher values of α at positions close to the magnetic null than in the more magnetized region of the plasma. This fractional increase in negative ion density during the off-phase is attributed to the enhanced dissociative electron attachment of highly excited oxygen molecules in the cooling plasma. The results show that close to the magnetic null the photodetached electron density decays quickly after the laser pulse, followed by a slow decay over a few microseconds governed by the negative ion temperature. However, in the magnetized regions of the plasma, this decay is more gradual. This is attributed to the different cross-field transport rates for electrons in these two regions. The resonance hairpin probe measurements of the photoelectron densities are compared directly to photoelectron currents obtained using a conventional Langmuir probe. There is good agreement in the general trends, particularly in the off-time.

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“…This technique appears to be similar to the microwave hairpin resonance probe 7, 11–14. The microwave hairpin resonance probe detects the resonance signal of a quarter‐wavelength resonator inserted in a discharge.…”

Section: Introductionmentioning

confidence: 99%

Optimised Plasma Absorption Probe for the Electron Density Determination in Reactive Plasmas

Scharwitz

Böke

Winter

2009

Plasma Processes & Polymers

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The plasma absorption probe (PAP) is a recently developed tool for the efficient determination of electron densities, especially in reactive plasmas. A dielectric cover protects this probe against the influences in reactive plasmas and it withstands conditions where Langmuir probes are easily damageable. The lack of adequate calibration constants and the occurrence of multiple absorption signals were two major drawbacks, which are successfully overcome in this work. Design variations are tested by numerical computation and the model‐based achievements are established in experiment. In this work, a redesigned PAP is presented, which is optimised for the easy determination of electron densities. The developed tool works fast and efficiently, in particular in discharges in reactive gases.

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Electron density modulation in an asymmetric bipolar pulsed dc magnetron discharge

Cited by 16 publications

References 30 publications

Performance of a Floating Hairpin Probe in Strongly Magnetized Plasma

Performance of a Floating Hairpin Probe in Strongly Magnetized Plasma

Resonance hairpin and Langmuir probe-assisted laser photodetachment measurements of the negative ion density in a pulsed dc magnetron discharge

Optimised Plasma Absorption Probe for the Electron Density Determination in Reactive Plasmas

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