TALIF measurements of hydrogen and deuterium surface loss probabilities on quartz in low pressure high density plasmas

Yang, Xuefeng; Kogut, D.; Couëdel, Lénaïc; Angot, Thierry; Roubin, P.; Faure, Jean-Baptiste; Cartry, Gilles

doi:10.1088/1361-6595/abd454

Cited by 7 publications

(5 citation statements)

References 59 publications

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“…In the light of recent calculations [81,82], the cross section of (R58) is close to or even lower than that of (R57). Thus, the commonly observed higher atomic density in D 2 plasmas should be justified by the difference in the transport properties of H and D atoms [83] and points to more intense AD and MN losses in D 2 plasmas, in agreement with the lower negative ion density for a given plasma density shown in figure 11(a).…”

Section: Negative Ion Destruction Reactionssupporting

confidence: 75%

Isotope effect in plasmas driven by ECR modules towards H^– and D^– production

Mitrou,

Svarnas,

Béchu

et al. 2023

Plasma Sources Sci. Technol.

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Optimization of negative ion sources operated with deuterium may be limited by the lack of data on fundamental processes. Insight can be obtained from studies focusing on a direct comparison of "H" _"2" and "D" _"2" plasmas. Herein, the ECR volume negative ion source Prometheus I is operated with both "H" _"2" and "D" _"2" gases and the properties of the generated plasmas are probed by means of electrostatic probes and laser induced photodetachment. A parametric study, involving pressure and microwave (2.45 GHz) power variation, reveals similar qualitative trends for most of the plasma properties in both gases. However, quantitavely, differences do exist for the plasma potential, the cold electron density and temperature, and the negative ion to electron density ratio. The hot electron population density and temperature are similar in both plasmas. EEDFs are thus isotope dependent at the lower energies in the ECR–heated plasmas, suggesting an effect that has been meagerly considered in the literature either experimentally or numerically. Overall, nearly the same maximal "H" ^"_" and "D" ^"_" negative ion densities are achieved (i.e., "4×" 〖"10" 〗^"9" " " 〖"cm" 〗^"-3" ). The results are eventually elucidated according to the ECR heating mechanisms and the production/destruction paths of the negative ions.

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Section: Negative Ion Destruction Reactionssupporting

confidence: 75%

Isotope effect in plasmas driven by ECR modules towards H^– and D^– production

Mitrou,

Svarnas,

Béchu

et al. 2023

Plasma Sources Sci. Technol.

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“…The former can be reduced by collecting more light on the cathode for example by using bigger optics for fluorescence collection [42]. The latter could be improved by increasing the gain of the PMT which causes an increase of the voltage between the dynode stages [42] in combination with gating the PMT as was for example done in [43].…”

Section: Two-photon Absorption Line Profile Measurementmentioning

confidence: 99%

TALIF at H⁻ ion sources for the determination of the density and EDF of atomic hydrogen

Merk

Wimmer²,

Briefi³

et al. 2023

J. Phys. D: Appl. Phys.

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The production of H- ions in negative ion sources relevant for particle accelerator facilities and neutral beam injection systems is based predominantly on the surface conversion of H atoms at a low work function surface covered with caesium (the plasma grid). Therefore, the H atom density n H and energy distribution function (EDF) close to the plasma grid determine the amount of surface produced H- ions. As a direct method for the density and EDF determination, two-photon absorption laser induced ﬂuorescence (TALIF) on H atoms was implemented at the ion source of the teststand BATMAN Upgrade being the ﬁrst time that this was accomplished at an H- ion source. Several challenges had to be overcome concerning the application of the diagnostic at the complex facility and the evaluation of the ﬂuorescence signals against a bright Hα background. The observed line proﬁles suggest a Maxwellian EDF with an H atom temperature of (2000 ± 500) K. The presence of highly energetic H atoms (measured by optical emission spectroscopy, OES) could not be resolved by the TALIF system due to the insuﬃcient signal-to-noise ratio. Atomic densities were measured for H2 and D2 plasmas for varying ion source parameters at BATMAN Upgrade resulting in values between 3×1018 m-3 and 1.1×1019 m-3 for hydrogen. For the operation with deuterium, 30% higher atomic densities are observed for similar ion source parameters which agree well with the previous results obtained with OES.

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“…Firstly introduced by Bokor et al in 1981 [18], TALIF of atomic hydrogen using two-photon excitation to the n = 3 electronically excited level, denoted H(n = 3) hereafter, and subsequent detection of the fluorescence at 656.3 nm, became of increasing use in the combustion [19][20][21][22][23][24][25] and plasma communities [26][27][28][29][30][31][32][33][34] to monitor atomic hydrogen with a good spatial resolution.…”

Section: Introductionmentioning

confidence: 99%

Depopulation mechanisms of atomic hydrogen in the n = 3 level following two-photon excitation by a picosecond laser

Duluard,

Invernizzi,

Hassouni

et al. 2024

Plasma Sources Sci. Technol.

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One of the major constraints of measurements of atomic hydrogen densities using Two-Photon Absorption Laser Induced Fluorescence (TALIF) in most plasma and combustion environments is the determination of fluorescence decay times (τfluo H), especially when using nanosecond-lasers or slow acquisition systems. Therefore, it is necessary to identify the depopulation processes of the laser excited level in order to correctly estimate τfluo H. In this study, depopulation mechanisms of atomic hydrogen excited by two-photon absorption to the n=3 level (H(n=3)) have been investigated using a picosecond-laser excitation and acquisition of fluorescence by a streak camera, which allowed for direct measurement of τfluo H and hence, the atomic hydrogen densities, in a H2 microwave plasma operating in the pressure range 20 – 300 Pa. By combining these measurements with a detailed H(n=3) collisional radiative depopulation model, it was found that full mixing amongst the H(n=3) sub-levels occurs in our discharge conditions, even at a pressure as low as 20 Pa. Moreover, it is also seen that the Lyman β line is only partially trapped, as its escape factor Λ31 decreases from 0.94 – 0.98 down to 0.58 – 0.86 while the measured atomic hydrogen density rises from 8±5×1019 m-3 to 9±6×1020 m-3. This means that the radiative decay rate of H(n=3) atoms varies with pressure and the classical Stern-Volmer method used to determine the quenching cross-section of excited H(n=3) in collisions with H2 molecules, σQ H(n=3)/H2, is not valid for our measurements. We used two different physics-based approaches, and show that the quenching cross-section σQ H(n=3)/H2 lies in the range 90 – 106×10-20 m2, which can be averaged as 98±8×10-20 m2. This substantially improved estimation of σQ H(n=3)/H2 obtained in this work will be useful for the accurate estimation of H(n=3) fluorescence decay times and therefore the atomic hydrogen densities.

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TALIF measurements of hydrogen and deuterium surface loss probabilities on quartz in low pressure high density plasmas

Cited by 7 publications

References 59 publications

Isotope effect in plasmas driven by ECR modules towards H^– and D^– production

Isotope effect in plasmas driven by ECR modules towards H^– and D^– production

TALIF at H⁻ ion sources for the determination of the density and EDF of atomic hydrogen

Depopulation mechanisms of atomic hydrogen in the n = 3 level following two-photon excitation by a picosecond laser

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TALIF measurements of hydrogen and deuterium surface loss probabilities on quartz in low pressure high density plasmas

Cited by 7 publications

References 59 publications

Isotope effect in plasmas driven by ECR modules towards H– and D– production

Isotope effect in plasmas driven by ECR modules towards H– and D– production

TALIF at H− ion sources for the determination of the density and EDF of atomic hydrogen

Depopulation mechanisms of atomic hydrogen in the n = 3 level following two-photon excitation by a picosecond laser

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Isotope effect in plasmas driven by ECR modules towards H^– and D^– production

Isotope effect in plasmas driven by ECR modules towards H^– and D^– production

TALIF at H⁻ ion sources for the determination of the density and EDF of atomic hydrogen