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Communication Dans Un Congrès Année : 2022

H$^{-}$ and D$^{-}$ production efficiency in a multi-dipole ECR-plasma source as a function of gas pressure

Résumé

The electron cyclotron resonance (ECR) negative ion source “Prometheus I” is operated either with high purity H2 (> 99.999%) or D2 (> 99.8%) to probe H$^{-}$ and D$^{-}$ ions, respectively, and examine the isotope effect within a wide range of gas pressure. These ions are predominantly formed in the bulk plasma by dissociative attachment (DA) of low-energy (cold) electrons to highly ro-vibrationally excited molecules. The latter result mainly from the radiative decay and excitation (EV) process sustained by high-energy (hot) electrons heated in the ECR zones. Langmuir probe and laser photo-detachment measurements are realized within the pressure range 0.27 to 2.67 Pa under constant microwave power (0.9 kW). It is revealed that: (i) the plasma potential, cold electron temperature, and cold electron density tend to be higher in deuterium; (ii) no pronounced difference in the hot electron density and temperature is found between the two plasmas; and (iii) overall a similar H$^{-}$ and D$^{-}$ negative ion yield (up to 6×10$^{9}$ cm$^{-3}$; under the present conditions) is achieved. However, for equal plasma densities an isotope effect is exhibited showing higher H$^{-}$ density over the entire pressure range. Finally, the n$_{H}$- / n ratio is constantly higher than the n$_{D}$- / n$_{e}$ one and they both peak around 1.33 Pa.

Dates et versions

hal-03654987 , version 1 (29-04-2022)

Identifiants

Citer

M. Mitrou, P. Svarnas, S. Béchu. H$^{-}$ and D$^{-}$ production efficiency in a multi-dipole ECR-plasma source as a function of gas pressure. 19th International Conference on Ion Sources, Sep 2021, Online, Canada. pp.012007, ⟨10.1088/1742-6596/2244/1/012007⟩. ⟨hal-03654987⟩
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