Open AccessH- and D- production efficiency in a multi-dipole ECR-plasma source as a function of gas pressure
Author(s) -
M Mitrou,
P. Svarnas,
Stéphane Béchu
Publication year - 2022
Publication title -
journal of physics. conference series
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.21
H-Index - 85
eISSN - 1742-6596
pISSN - 1742-6588
DOI - 10.1088/1742-6596/2244/1/012007
Subject(s) - atomic physics , chemistry , langmuir probe , excited state , deuterium , electron cyclotron resonance , plasma , ion , electron temperature , kinetic isotope effect , electron , analytical chemistry (journal) , plasma diagnostics , physics , organic chemistry , quantum mechanics , chromatography
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.