A study of VUV emission and the extracted electron-ion ratio in hydrogen and deuterium plasmas of a filament-driven H−/D− ion source

Komppula, J.; Tarvainen, O.; Kalvas, Taneli; Koivisto, H.; Myllyperkiö, Pasi; Toivanen, V.

doi:10.1063/1.5095475

Cited by 3 publications

(2 citation statements)

References 31 publications

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“…[20] the authors concluded that: "The volume production of H − is enhanced by gas mixing because the cold electron density near the extraction increases as heavier ions bring cold electrons through the magnetic filter to the low-energy plasma chamber". The given explanation contradicts the conclusion by Komppula et al arguing that volume production of D − ions in a multicusp ion source is limited by the diffusion of the heavier isotope across the transverse filter field [21]. Thus, alternative explanations for the H − beam current enhancement by the Xe admixture should be sought.…”

Section: On the Possibility Of Ion Pair Production In Plasma Ion Sourcesmentioning

confidence: 63%

Photo-assisted O− and Al− production with a cesium sputter ion source

Tarvainen

Kronholm

Laitinen

et al. 2021

Seventh International Symposium on Negative Ions, Beams and Sources (Nibs 2020)

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It has been recently proposed that the production of negative ions with cesium sputter ion sources could be enhanced by laser-assisted resonant ion pair production. We have tested this hypothesis by measuring the effect of pulsed diode lasers at various wavelengths on the O − and Al − beam current produced from Al 2 O 3 cathode of a cesium sputter ion source. The experimental results provide evidence for the existence of a wavelength-dependent photo-assisted enhancement of negative ion currents but cast doubt on its alleged resonant nature as the effect is observed for both O − and Al − ions at laser energies above a certain threshold. The beam current transients observed during the laser pulses suggest that the magnitude and longevity of the beam current enhancement depends on the cesium balance on the cathode surface. It is shown that the ions produced by the laser exposure originate from slightly different potential than the surface produced ions, which allows us to constrain the underlying physical mechanisms. It is concluded that the photo-assisted negative ion production could be of practical importance as it can more than double the extracted beam current under certain operational settings of the cesium sputter ion source. We discuss experiments designed to confirm or dispute the relevance of the ion pair production for negative ion production with cesium sputter ion sources and the possibility of ion pair production explaining the beneficial effect of xenon admixture on the negative ion yield of an RF-driven H − ion source.

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Section: On the Possibility Of Ion Pair Production In Plasma Ion Sourcesmentioning

confidence: 63%

Photo-assisted O− and Al− production with a cesium sputter ion source

Tarvainen

Kronholm

Laitinen

et al. 2021

Seventh International Symposium on Negative Ions, Beams and Sources (Nibs 2020)

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“…Neither the spectra nor the volumetric rates of ionization, excitation, production of high vibrational states, and dissociation between the two isotopes showed any significant difference. It is therefore suggested that in this source, the observed difference between the H − and D − production through dissociative electron attachment (DEA) is attributed most likely to the difference in the diffusion properties of hydrogen and deuterium [27].…”

Section: Introductionmentioning

confidence: 99%

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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Emission spectroscopy of negative hydrogen ion sources: From VUV to IR

Wünderlich

Briefi

Friedl

et al. 2021

Review of Scientific Instruments

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The target parameters of negative ion sources regarding the current of extracted negative ions, the current of co-extracted electrons, the pulse duration, the duty cycle, and the availability of the system can be rather strict. Knowledge of plasma parameters such as the electron temperature and the electron density and also properties of molecules or photon fluxes can provide essential insights into the ion source physics needed for reaching the target parameters. Emission spectroscopy is a non-invasive tool enabling access to line-of-sight averaged values of plasma parameters. This paper gives an overview of the application of emission spectroscopy in the visible range, extended for long wavelengths to the near-IR and for short wavelengths to the vacuum ultraviolet (VUV)/UV range. The amount of information to be gained from measured emission spectra is directly correlated with the effort invested for calibrating the system. Examples are given, ranging from simple monitoring to the complex evaluation of molecular spectra and the determination of highly energetic photon fluxes in the VUV/UV range. Additional emphasis is laid on the population models needed for the interpretation of measured spectra.

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A study of VUV emission and the extracted electron-ion ratio in hydrogen and deuterium plasmas of a filament-driven H−/D− ion source

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 3 publications

References 31 publications

Photo-assisted O− and Al− production with a cesium sputter ion source

Photo-assisted O− and Al− production with a cesium sputter ion source

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

Emission spectroscopy of negative hydrogen ion sources: From VUV to IR

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A study of VUV emission and the extracted electron-ion ratio in hydrogen and deuterium plasmas of a filament-driven H−/D− ion source

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 3 publications

References 31 publications

Photo-assisted O− and Al− production with a cesium sputter ion source

Photo-assisted O− and Al− production with a cesium sputter ion source

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

Emission spectroscopy of negative hydrogen ion sources: From VUV to IR

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