A method for measuring fast time evolutions of the plasma potential by means of a simple emissive probe

Iizuka, Satoru; Michelsen, Poul; Rasmussen, Jens Juul; Schrittwieser, R.; Hatakeyama, Rikizo; Saeki, Koichi; Sato, Naoyuki

doi:10.1088/0022-3735/14/11/017

Cited by 41 publications

(27 citation statements)

References 7 publications

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“…[26][27][28][29][30][31][32][33][34][35] As the name suggests, an emissive probe is sufficiently hot to emit electrons via the thermionic emission mechanism, where the current density is approximately described by the Richardson-Dushman equation (cf. e.g.…”

Section: Emissive Probe Techniquesmentioning

confidence: 99%

Plasma potential mapping of high power impulse magnetron sputtering discharges

Rauch

Mendelsberg

Sanders

et al. 2012

Journal of Applied Physics

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Pulsed emissive probe techniques have been used to determine the plasma potential distribution of high power impulse magnetron sputtering (HiPIMS) discharges. An unbalanced magnetron with a niobium target in argon was investigated for pulse length of 100 µs at a pulse repetition rate of 100 Hz, giving a peak current of 170 A. The probe data were taken with a time resolution of 20 ns and a spatial resolution of 1 mm. It is shown that the local plasma potential varies greatly in space and time. The lowest potential was found over the target's racetrack, gradually reaching anode potential (ground) several centimeters away from the target. The magnetic pre-sheath exhibits a funnel-shaped plasma potential resulting in an electric field which accelerates ions toward the racetrack. In certain regions and times, the potential exhibits weak local maxima which allow for ion acceleration to the substrate. Knowledge of the local E and static B fields lets us derive the electrons' E × B drift velocity, which is about 10 5 m/s and shows structures in space and time.

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Section: Emissive Probe Techniquesmentioning

confidence: 99%

Plasma potential mapping of high power impulse magnetron sputtering discharges

Rauch

Mendelsberg

Sanders

et al. 2012

Journal of Applied Physics

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“…An additional often neglected or underestimated fact is that the floating potential of a cold probe shifts towards more negative values if there are additional electron drifts or beams in the plasma [4], e.g. due to stationary potential structures (such as double layers) or runaway electrons.…”

Section: Introductionmentioning

confidence: 99%

New Results on a Laser‐Heated Emissive Probe

Ioniţă

Balan

Windisch

et al. 2008

Contrib. Plasma Phys.

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Direct measurements of the plasma potential with high temporal and spatial resolution are only possible with special probes whose floating potential becomes equal to the plasma potential. One of these probes is the emissive probe which can be heated to electron emission. This leads to the effect that the plasma electron current towards the probe is compensated by an equal electron emission current flowing from the probe into the plasma which shifts the probe floating potential to the value of the plasma potential. While emissive probes are usually realized by heatable loops of wires of a refractory metal like tungsten or thoriated tungsten, we have developed various types of probes whose tip can be heated by an infrared laser beam. This offers several advantages like higher emission, longer lifetime and faster time response. Here we report on the latest development of a laser-heated emissive probe and on measurements with it in a magnetized helicon plasma.

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“…All the problems, mentioned in section 2, can be circumvented when we use a probe, which not only passively registers the flux of plasma electrons but actively emits an electron current [6,7,8,9,10]. (The ion current can be entirely neglected in these considerations.)…”

Section: The Advantages Of Electron Emissive Probesmentioning

confidence: 99%

“…An additional restriction lies in the fact that a high input impedance R is needed to determine the floating potential of any probe. This, together with inevitable cable and instrument capacities C i , might lead to a rather high time constant RC i which reduces the upper cut-off frequency of fluctuations, which can be picked up by such a probe [9]. An emissive probe is usually realised by a small loop of tungsten wire, carried by a double-bore ceramic tube, and heated by an external current so that the W-wire becomes emissive.…”

Section: The Advantages Of Electron Emissive Probesmentioning

confidence: 99%