Experimental investigation of the change of the electron saturation current of a dc-heated emissive probe

Marek, A.; Picková, I.; Kudrna, P.; Tichý, M.; Apetrei, R.; Olenici, S. B.; Gstrein, Ramona; Schrittwieser, R.; Ioniţă, C.

doi:10.1007/s10582-006-0306-0

Cited by 16 publications

(21 citation statements)

References 10 publications

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“…This dependence of I co (T p ) with the wire temperature T p in Fig. 1 has been previously reported by different authors but has not received a fully satisfactory explanation yet [14]. As proposed in [10], Fig.…”

Section: Resultssupporting

confidence: 49%

“…We have concluded that V p \ could be determined by using hot emissive Langmuir probes plotting V F (T P ) as a function of T p (or equivalently, probe heating current In) as discussed in [8]- [10] and [14]. The abrupt change in the slope of V F (T P ) that appears at temperature T ph where V F (T pl ) ~ V ph determines the value of the plasma potential.…”

Section: Discussionmentioning

confidence: 97%

“…Additionally, the U-shaped wire is small; only a fraction of its surface directly points toward the plasma, and this would increase the reduction of the effective thermionic current also equivalent to a lower emitting surface. This would explain that probes made of wires with varied diameters provide the same value of V p] for different heating currents In [14].…”

Section: Discussionmentioning

confidence: 99%

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Emissive Langmuir probes in the strong emission regime for the determination of the plasma properties

Tierno

Doménech

Donoso

et al. 2012

2012 Abstracts IEEE International Conference on Plasma Science

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Abstract-The determination of the plasma potential V^i of unmagnetized plasmas by using the floating potential of emissive Langmuir probes operated in the strong emission regime is investigated. The experiments evidence that, for most cases, the electron thermionic emission is orders of magnitude larger than the plasma thermal electron current. The temperature-dependent floating potentials of negatively biased V p < V^i emissive probes are in agreement with the predictions of a simple phenomenological model that considers, in addition to the plasma electrons, an additional electron group that contributes to the probe current. The latter would be constituted by a fraction of the repelled electron thermionic current, which might return back to the probe with a different energy spectrum. Its origin would be a plasma potential well formed in the plasma sheath around the probe, acting as a virtual cathode or by collisions and electron thermalization processes. These results suggest that, for probe bias voltages close to the plasma potential V p ~ V^i, two electron populations coexist, i.e., the electrons from the plasma with temperature T e and a large group of returned thermionic electrons. These results question the theoretical possibility of measuring the electron temperature by using emissive probes biased to potentials V p < V^i.

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Section: Resultssupporting

confidence: 49%

Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Emissive Langmuir probes in the strong emission regime for the determination of the plasma properties

Tierno

Doménech

Donoso

et al. 2012

2012 Abstracts IEEE International Conference on Plasma Science

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“…[1][2][3]5]. This wire is heated up to the electron thermoionic emission using a DC current and is electrically biased as the collecting probes.…”

Section: Introductionmentioning

confidence: 99%

“…For large enough wire temperatures this emitted electron current produces a steeper transition in the IV curve. Then, this transition from electron emission to collection creates an abrupt jump in I p (V p ) that allows an accurate determination of the plasma potential V sp , currently determined from the IV curves by means of either, the floating point or the inflection point methods [1,[3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Measurements of Plasma Properties Using Fast Sweep Langmuir Probes in Unmagnetized Weakly Ionized Plasmas

Troll

Conde

Criado

et al. 2010

Contrib. Plasma Phys.

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The performances of a simple circuit for fast sweep measurements using collecting and emissive Langmuir probes are evaluated. The probes are biased by means of a time dependent ramp voltage signal with a variable pulse frequency and the current voltage curves are measured along the increasing flange of this sawtooth voltage. The response of this fast probe polarization circuit was verified under actual experimental conditions by measuring the properties of a stationary Maxwellian plasma produced by means of a glow discharge. The results are independent of the experimental conditions and essentially rely on the discharge properties for polarization pulse repetition rates below a threshold. This upper bound lies below the ion plasma frequency and is related with the faster time scale involved in the sawtooth signal probe bias voltage. The motion of ions would not follow the rapid change of the electric field around the probe associated to the short decreasing edge of the sawtooth polarization voltage and, therefore, the probe perturbs the local electric field. We conclude that these time scales should be considered for the interpretation of these measurements in addition to the electron and ion plasma frequencies in fast sweep Langmuir probe techniques. We conclude that these time scales should be considered for the interpretation of these measurements in addition to the electron and ion plasma frequencies in fast Langmuir probe techniques.

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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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Experimental investigation of the change of the electron saturation current of a dc-heated emissive probe

Cited by 16 publications

References 10 publications

Emissive Langmuir probes in the strong emission regime for the determination of the plasma properties

Emissive Langmuir probes in the strong emission regime for the determination of the plasma properties

Measurements of Plasma Properties Using Fast Sweep Langmuir Probes in Unmagnetized Weakly Ionized Plasmas

New Results on a Laser‐Heated Emissive Probe

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