Plasma electron density measurements by the laser- and collision-induced fluorescence method

Tsuchida, Koji; Miyake, Shoji; Kadota, K.; Fujita, J.

doi:10.1088/0032-1028/25/9/003

Cited by 36 publications

(19 citation statements)

References 9 publications

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“…The two techniques for measuring plasma parameters non-intrusively are Microwave Interferometry (MWI) 7 and Laser-Induced-Fluorescence (LIF) 8 coupled with Laser-Collision Induced Fluorescence (LCIF) 9,10 . As these measurements are remote from the region whose characteristics are desired, they would seem an ideal solution to the problems of in-situ probe perturbation of an existing environment.…”

Section: Introductionmentioning

confidence: 99%

“…The method we propose is largely insensitive to pressure variations as described and thus is not subject to these drawbacks. The fact that these results can be used existing probe/object/wall measurements to determine the sheath can be extremely useful in the analysis of collected probe data.The two techniques for measuring plasma parameters non-intrusively are Microwave Interferometry (MWI) 7 and Laser-Induced-Fluorescence (LIF) 8 coupled with Laser-Collision Induced Fluorescence (LCIF) 9,10 . As these measurements are remote from the region whose characteristics are desired, they would seem an ideal solution to the problems of in-situ probe perturbation of an existing environment.…”

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confidence: 99%

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On the Non-Intrusive Determination of Electron Density in the Sheath of a Spherical Probe

Walker¹,

Fernsler²,

Blackwell³

et al. 2007

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Standard Form 298 (Rev. 8-98)Prescribed by ANSI Std. Z39.18Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER A new method of determining probe/antenna plasma sheath parameters has been developed. For low neutral pressure environments in the absence of a magnetic field, the method provides these quantities from a probe/antenna surface through the sheath, pre-sheath, and into the bulk plasma. For high pressure environments, where conventional resonances are strongly damped, it can determine bulk plasma density. The paper cites commonly used methods of finding electron density/temperature and points out the inadequacy of each to make sheath measurements in the general case. The primary advantage of the method lies in the fact that a non-perturbative rf signal is applied to the probe/antenna for the determination and this makes the measurement independent of complicating influences such as secondary electron emission, surface conditions, and ion mass. Because of this, the ac impedance depends on frequency but not on the dc voltage unlike a typical Langmuir probe. In this paper we concentrate on the low pressure regime. REPORT TYPE 1. REPORT DATE (DD-MM-YYYY) TITLE AND SUBTITLE AUTHOR(S) PERFORMING ORGANIZATION REPORT NUMBER PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) SPONSOR / MONITOR'S ACRONYM(S) 9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) SPONSOR / MONITOR'S REPORT NUMBER(S)12 20-04-2007Memorandum Report I. AbstractOver the last year the Charged Particle Physics Branch (Code 6750) has developed a technique which differs significantly from conventional techniques used to determine plasma density and temperature. For low neutral pressure environments in the absence of a magnetic field, the method provides these quantities from a probe/antenna surface through the sheath, pre-sheath, and into the bulk plasma. For high pressure environments, where conventional resonances are strongly damped, it can determine bulk plasma density. The technique can be employed with a planar, cylindrical or spherical probe/antenna geometry using a low l...

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Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

On the Non-Intrusive Determination of Electron Density in the Sheath of a Spherical Probe

Walker¹,

Fernsler²,

Blackwell³

et al. 2007

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“…Chall et al [1] measured n e ≈ 5 × 10 12 cm -3 from the time decay rate of the fluorescence signal at the laser wavelength at λ = 587.6 nm in an argon arc plasma of T e ≈ 0.4 eV with small admixture of helium. The electron density in the range n e = 10 11 -10 12 cm -3 in a helium plasma of T e ≈ 5 eV was determined by Tsuchida et al [2] from the ratio of time integrated collision-induced (λ = 667.8 nm) and laserinduced fluorescence signals upon the laser excitation at λ = 501.6 nm in singlet helium. Shcheglov et al [3] determined electron densities of n e ≈ 5 × 10 11 cm -3 in an argon plasma (T e ≈ 10 eV) with helium content using relative collision-induced signals I 388.9 nm /I 706.5 nm upon laser excitation at λ = 587.6 nm.…”

Section: Derivation Of the Electron Density From Laser-and Collision-mentioning

confidence: 99%

“…Hence, at higher temperatures the signals will become poorer and the fits less reliable. In this case additional analysis by using the ratio of the time integrated laser-and collision-induced fluorescence signals can be applied [2]. (From the experimental point of view this additional measurement would require a spatial separation of fluorescence photons at both wavelengths e.g.…”

Section: Derivation Of the Electron Density From Laser-and Collision-mentioning

confidence: 99%

“…The method relies on resonant laser pumping of some levels and analyzing their fluorescence after the end of the laser pulse. Such measurements were already performed in low temperature plasmas with some content of atomic helium [1,2,3]. In this paper, we discuss the applicability of this method in the fusion edge plasma in the density range of 10 12 -10 13 cm -3 when exciting helium atoms with a laser at the wavelength of λ = 388.9 nm tuned to the triplet transition 2 3 S → 3 3 P o and observing the fluorescence light at the laser wavelength and at λ = 587.6 nm (3 3 D → 2 3 P o ).…”

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confidence: 99%

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LIF Measurements on an Atomic Helium Beam in the Edge of a Fusion Plasma—possible derivation of the electron density

Krychowiak

Mertens

Schweer

et al. 2008

AIP Conference Proceedings

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Abstract. Local values of the electron density and temperature in the edge of a fusion plasma can be derived with high space and time resolution by the use of line radiation of atomic helium beams. The accuracy of this method is mainly limited by the uncertainties in the collisional-radiative model which is needed in order to obtain both plasma parameters from the measured relative intensities of atomic helium lines. Combination of a helium beam with a pulsed high-power laser provides a possibility of n e measurement which does not require a detailed knowledge of the collisional-radiative model. The method relies on resonant laser pumping of some levels and analyzing their fluorescence after the end of the laser pulse. Such measurements were already performed in low temperature plasmas with some content of atomic helium [1,2,3]. In this paper, we discuss the applicability of this method in the fusion edge plasma in the density range of 10 12 -10 13 cm -3 when exciting helium atoms with a laser at the wavelength of λ = 388.9 nm tuned to the triplet transition 2 3 S → 3 3 P o and observing the fluorescence light at the laser wavelength and at λ = 587.6 nm (3 3 D → 2 3 P o ). A first test measurement at the TEXTOR tokamak in Jülich performed by use of an excimer-pumped dye laser in connection with a thermal helium beam is shown and discussed.

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Laser-Induced Fluorescence Measurements of Number Densities of Neutral and Ionized Metal Atoms

Lins

1990

Physics and Applications of Pseudosparks

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Plasma electron density measurements by the laser- and collision-induced fluorescence method

Cited by 36 publications

References 9 publications

On the Non-Intrusive Determination of Electron Density in the Sheath of a Spherical Probe

On the Non-Intrusive Determination of Electron Density in the Sheath of a Spherical Probe

LIF Measurements on an Atomic Helium Beam in the Edge of a Fusion Plasma—possible derivation of the electron density

Laser-Induced Fluorescence Measurements of Number Densities of Neutral and Ionized Metal Atoms

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