Production of hydrogen negative ions in an ECR volume source: balance between vibrational excitation and ionization

Aleiferis, S.; Svarnas, P.; Béchu, Stéphane; Tarvainen, O.; Bacal, M.

doi:10.1088/1361-6595/aabf1b

Cited by 21 publications

(38 citation statements)

References 57 publications

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“…Therefore, we use an ECR plasma as a substitute to the helicon plasma. Five ECR dipolar plasma sources implemented in PROMETHEUS-I reactor 78 give similar n − i /n e density ratio as RAID, 0.25 and 0.22, respectively, at the same working conditions. Even though the absolute density in the PROMETHEUS-I 79 reactor is lower ∼ 5 × 10 15 m −3 than in the RAID reactor, it is obtained at lower input power, 0.9 kW instead of 5 kW.…”

Section: Many Authors Have Used Laser-based High Resolution Methods To Perform Direct Measurements Of V Densitiesmentioning

confidence: 92%

“…) is calculated with the DEA cross section given by Celiberto et al 9 (extrapolated above v =6), and the electron energy distribution function (EEDF), bi-maxwellian, is drawn out from previous experiments 51,78 in similar experimental conditions. The result of this coarse evaluation, presented in Fig.…”

Section: The Effect Of Recombinative Desorption On the Negative Ion Production Yieldmentioning

confidence: 99%

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Direct measurements of electronic ground state ro-vibrationally excited D2 molecules produced on ECR plasma-facing materials by means of VUV-FT absorption spectroscopy

Béchu

Lemaire

Gavilan

et al. 2020

Journal of Quantitative Spectroscopy and Radiative Transfer

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Ro-vibrationally excited molecules of deuterium are involved in non-equilibrium chemical reactions in divertor region of tokamak, molecular assisted recombination, or in neutral beam injector to produce negative ion, dissociative electron attachment, for fusion plasmas. These molecules produced both in a plasma volume and on surfaces are no longer in their electronic ground state X 1 + g (v " 0, J " ) and populate non-uniformly different vibrational (v ) and rotational levels (J ). The high resolution VUV Fourier Transform spectrometer of the DESIRS beam line (SOLEIL synchrotron) is applied to directly scrutinize the ro-vibrationally excited levels of the D 2 ground state from v = 0 to 10 and J up to 8 in an electron cyclotron resonance (ECR) cold plasma. This is performed for different plasma-facing materials, i.e. quartz, tantalum, tungsten, and stainless steel, in order to compare their relative impact in molecular excitation through recombinative desorption from surfaces. A significant effect of these materials on the absolute distribution of the vibrationally states has been found above v > 3. The experimental detection limit for Quartz is v = 7 whereas tungsten and stainlees steel excite the molecules up to v = 9 and tantalum up to v = 10. The use of a bare, temperature-controlled surface of Quartz as a reference, compared to metallic surfaces, allows us to determine the relative production of these excited levels. The recombinative desorption rate on tungsten and stainless steel compared to quartz is ∼2.6 higher and reaches ∼5 for tantalum.

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Section: Many Authors Have Used Laser-based High Resolution Methods To Perform Direct Measurements Of V Densitiesmentioning

confidence: 92%

Section: The Effect Of Recombinative Desorption On the Negative Ion Production Yieldmentioning

confidence: 99%

Direct measurements of electronic ground state ro-vibrationally excited D2 molecules produced on ECR plasma-facing materials by means of VUV-FT absorption spectroscopy

Béchu

Lemaire

Gavilan

et al. 2020

Journal of Quantitative Spectroscopy and Radiative Transfer

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“…Figure 6 shows the side view (left) and top view (right) of the experimental ECR source. 22,23 It consists of a cube- are taken at the center axis 6.5 cm below the magnets. The plasma is considered to only exist in the volume below the magnets due to the presence of grounded guides above the magnets.…”

Section: Validation Of Gmnhis With Experiments For Ecr Dischargementioning

confidence: 99%

Benchmarking and validation of global model code for negative hydrogen ion sources

et al. 2018

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Benchmarking and validation are prerequisite for using simulation codes as predictive tools. In this work, we have developed a Global Model for Negative Hydrogen Ion Source (GMNHIS) and performed benchmarking of GMNHIS against another independently developed code, Global Enhanced Vibrational Kinetic Model (GEVKM). This is the first study to present quite comprehensive benchmarking test of this kind for models of negative hydrogen ion sources (NHIS), and very good agreement has been achieved for electron temperature, vibrational distribution function (VDF) of hydrogen molecules, and H e nn − ratio. The small discrepancies in number densities of negative hydrogen ions, positive ions, as well as hydrogen atoms can be attributed to the differences in the predicted electron number density for given discharge power. Higher electron number density obtained with GMNHIS is possibly due to fewer dissociation channels accounted for in GMNHIS, leading to smaller energy loss. In addition, we validated GMNHIS against experimental data obtained in an electron cyclotron resonance (ECR) discharge used for H − production. The model qualitatively (and even quantitatively for certain conditions) reproduces the experimental H − number density. The H − number density as a function of pressure first increases at pressures below 12 mTorr, and then saturates for higher pressures. This dependence was analyzed by evaluating contributions from different reaction pathways to the creation and loss of the H − ions. The developed codes can be used for predicting the H − production, improving the performance of NHIS, and ultimately optimizing the parameters of negative ion beams for ITER.

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“…If the negative ion to electron n i -/n e density ratio is considered, results obtained at similar plasma conditions and position in PROMETHEUS-I reactor (see Sect. 3.1) [67] (a network of five identical ECR dipolar sources) and in the RAID reactor [76] are comparable: 0.18 and 0.225, respectively. In consequence, the plasma features, produced by an ECR dipolar source, can be considered similar enough to the one obtained in the RAID reactor to allow an investigation of the ECR plasma rather than the helicon plasma when plasma diagnostic cannot be set up for RAID.…”

Section: Experimental Investigation On Recombinative Desorption Mechanism In An Ecr (245 Ghz) Plasmamentioning

confidence: 97%

“…Many other authors [63][64][65][66][67] have developed similar approaches for a better understanding of the formation of negative H − and D − in different sources.…”

Section: Global Models and Relevant Elementary Processes In Caesium-free Nis: Early Studiesmentioning

confidence: 99%

Latest experimental and theoretical advances in the production of negative ions in caesium-free plasmas

et al. 2021

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This topical review gathers the last updates concerning caesium-free negative ion sources presented during the 63rd Course of the International school of Quantum Electronics of the Ettore Majorana Foundation and European collaborative works related to these lectures. Hence, beyond the frame of this course this topical review addresses both theoretical and experimental work performed during these last few years and complexities represented by the conception of a negative ion source ranging from the creation of negative ions to their neutralization.

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Production of hydrogen negative ions in an ECR volume source: balance between vibrational excitation and ionization

Abstract: This is a self-archived version of an original article. This version may differ from the original in pagination and typographic details.

Cited by 21 publications

References 57 publications

Direct measurements of electronic ground state ro-vibrationally excited D2 molecules produced on ECR plasma-facing materials by means of VUV-FT absorption spectroscopy

Direct measurements of electronic ground state ro-vibrationally excited D2 molecules produced on ECR plasma-facing materials by means of VUV-FT absorption spectroscopy

Benchmarking and validation of global model code for negative hydrogen ion sources

Latest experimental and theoretical advances in the production of negative ions in caesium-free plasmas

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