Spectroscopic Determination of Electron Temperature in a Helium Plasma

Vries, R F de

doi:10.1063/1.1761689

Cited by 19 publications

(7 citation statements)

References 4 publications

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“…It has been suggested that the deviation from the corona model is primarily due to the metastable contributions. 13,14 Using Eq. ͑6͒ and assuming that the population of the 2 3 S and 2 1 S metastable states remains small when compared to the ground population, the line ratio function including metastable contributions can be written as…”

Section: ϫ3mentioning

confidence: 99%

“…Since first proposed by Cunningham, 10 this line ratio diagnostic has been used to measure electron temperatures in many plasma conditions. [11][12][13][14][15][16][17] Recently, this technique has been considerably improved and extended to high-density, fusion edge plasmas. 18 -23 Until now, the validity of this technique to measure the electron temperature in rf generated plasmas has never been established.…”

Section: Introductionmentioning

confidence: 99%

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Electron temperature measurement by a helium line intensity ratio method in helicon plasmas

2001

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Electron temperature measurements in helicon plasmas are difficult. The presence of intense rf fields in the plasma complicates the interpretation of Langmuir probe measurements. Furthermore, the non-negligible ion temperature in the plasma considerably shortens the lifetime of conventional Langmuir probes. A spectroscopic technique based on the relative intensities of neutral helium lines is used to measure the electron temperature in the HELIX ͑Hot hELicon eXperiment͒ plasma ͓P. A. Keiter et al., Phys. Plasmas 4, 2741 ͑1997͔͒. This nonintrusive diagnostic is based on the fact that electron impact excitation rate coefficients for helium singlet and triplet states differ as a function of the electron temperature. The different aspects related to the validity of this technique to measure the electron temperature in rf generated plasmas are discussed in this paper. At low plasma density (n e р10 11 cm Ϫ3), this diagnostic is believed to be very reliable since the population of the emitting level can be easily estimated with reasonable accuracy by assuming that all excitation originates from the ground state ͑steady-state corona model͒. At higher density, secondary processes ͑excitation transfer, excitation from metastable, cascading͒ become more important and a more complex collisional radiative model must be used to predict the electron temperature. In this work, different helium transitions are examined and a suitable transition pair is identified. For an electron temperature of 10 eV, the line ratio is measured as a function of plasma density and compared to values predicted by models. The measured line ratio function is in good agreement with theory and the data suggest that the excitation transfer is the dominant secondary process in high-density plasmas.

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Section: ϫ3mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Electron temperature measurement by a helium line intensity ratio method in helicon plasmas

2001

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“…T e measurement by using HeI line intensity ratios was proposed by Cunningham in conjunction with a corona model [18] and the HeI line intensity ratio method was applied in several devices [19][20][21][22]. Recent progress of CR modeling of He allow to measure n e as well as T e with better accuracy.…”

Section: Introductionmentioning

confidence: 99%

2D Measurement of Edge Plasma Dynamics by Using High‐Speed Camera Based on HeI Line Intensity Ratio Method

Ohno

Miyamoto

Kajita

et al. 2010

Contrib. Plasma Phys.

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In order to investigate dynamic plasma behaviors in scrape-off layer (SOL) regions, such as ELMs and plasma blobs, we have developed a 4-channel high-speed camera equipped with four interference filters to obtain 2D successive images of spectral intensity of He I emission lines at 667.8 nm, 706.5 nm and 728.1 nm in addition to HeII at 656.0 nm. By using calculated results based on a Collisional Radiative (CR) model for He, the intensity ratios of the He I lines (728.1/706.5 and 667.8/706.5), provides 2D distributions of the electron temperature and density. The 2D profiles of electron density and temperature reconstructed from 2D images of He I emission lines taken in a small tokamak, HYBTOK-II were compared with those measured with the triple probe in order to evaluate the accuracy of this diagnostics. Electron density and temperature measured with the 4-channel high-speed camera are in good agreement with those obtained with the triple probe.

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“…(4) Ej is the excitation energy in electron volts and P(E/kTe) is the average gaunt factor which is a slowly varying function of frequency and Te; when E/kTe> 10 P(E/kTe) =O *066/(E/kTe)1/2. or This expression can be used for the measurement of electron temperature if the plasma is optically thin and excitations are by electron impact from the ground state and Wilson (1962) and de Vries and Mewe (1966) have shown that the approximate condition that has to be satisfied is…”

Section: Methods Of Measurementmentioning

confidence: 99%

Measurement of electron temperature in glow discharge in transverse magnetic field by spectroscopic method

Sadhya

Sen

1980

J. Phys. D: Appl. Phys.

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The electron temperature in the positive column of a glow discharge in hydrogen and helium as a function of the transverse magnetic field in the range of 0 to 1000 G has been obtained by measuring the intensities of two spectral lines having the same lower level. Since the electron number density in the column is of the order of 1010 cm-3 the semicorona model suitably modified has been used to calculate the plasma electron temperature in a magnetic field. For lower values of the field the variation of the electron temperature with the field can be represented by an expression deduced by Sen and Gupta (1971) following Beckman's theory. The electron energy distribution in a transverse field can thus be nearly Maxwellian.

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Spectroscopic Determination of Electron Temperature in a Helium Plasma

Abstract: Optical excitation functions measured in collision chamber experiments should be applied with caution on plasma diagnostics. This is illustrated for the upper level (41S) of λ5048 of neutral helium.

Cited by 19 publications

References 4 publications

Electron temperature measurement by a helium line intensity ratio method in helicon plasmas

Electron temperature measurement by a helium line intensity ratio method in helicon plasmas

2D Measurement of Edge Plasma Dynamics by Using High‐Speed Camera Based on HeI Line Intensity Ratio Method

Measurement of electron temperature in glow discharge in transverse magnetic field by spectroscopic method

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