Les sources d'ions à excitation électrique de haute fréquence

Abstract

2014 Les sources à excitation électrique de haute fréquence (ou sources H. F.), délivrent des courants intenses d'ions positifs ; elles sont couramment employées dans les accélérateurs de particules, les microscopes ioniques, les appareils thermonucléaires. Elles produisent des ions presque monocinétiques et sont donc intéressantes pour la spectroscopie de masses. Les publications qui les concernent, assez nombreuses, appartiennent à des domaines très divers, et les données relatives à ces sources s'insèrent souvent dans une étude à caractère plus général. Il nous a paru utile d'effectuer une synthèse de cet ensemble assez disparate, afin d'établir les conditions pratiques d'emploi de ces sources. Après avoir décrit les modèles usuels de sources H. F., nous procédons à leur classement selon le mécanisme de la décharge (annulaire, linéaire, avec ou sans un champ magnétique auxiliaire). Le problème de l'extraction des ions est ensuite abordé ; nous passons en revue les principaux systèmes d'extraction, ainsi que les paramètres qui conditionnent l'intensité du faisceau extrait. Nous indiquons enfin quelle est la valeur de l'énergie moyenne des ions et la dispersion autour de cette valeur moyenne. Abstract. 2014 Sources excited by high frequency oscillators (or H. F. sources) give high currents of positive ions, they are of current use in particle accelerators, ion microscopes, thermonuclear apparatus. Producing nearly monoenergetic ions, they are of value for mass spectroscopy. The papers about them, rather numerous, are related to very different matters, so that the data on these sources are found often in a more general study. We have considered that a synthesis of this rather varied material would be useful, in order to state the conditions of practical use of the sources. After describing the usual models of H. F. sources, we class them according to the mechanism of the discharge (annular, linear, with or without addition of a constant magnetic field). Then, we describe the problem of the extraction of ions ; we describe the principal extraction systems, and we review the various parameters influencing the intensity of the extracted stream. Finally, we give the average ion energy, and the dispersion around this average value.

Metastable He+(2S) production by a RF ion source

“…In the first approximation, V, does not change the plasma state (Reifenschweiler and Frohner 1964). However V, affects R,, by quenching metastable ions in the accelerating gap between the plasma limit and the internal end of the exit canal (Blanc and Degeilh 1961) (see figure 3 ) .…”

Sputtering and electron emission under mercury ion bombardment in the energy range 15-100 keV

“…The ion beam was not magnetically analysed to obtain velocity or mass separation, but it was deflected electrostatically to remove any energetic neutral atoms formed by charge exchange. Although the energy spread of ions from an rf source can be as much as 100 eV (Blanc and Degeilh 1961) this is small compared with the beam energies.…”

RF and Microwave Ion Sources Study at Institute of Modern Physics

“…During those years, different designs were tested. However, one of the major drawbacks of RF-produced plasma was the large energy dispersion (above tens of eV), which caused chromatic aberration and therefore limited the formation of a high-brightness high spatial resolution ion beam for micro-nano-scale applications [23,24]. Ero [25] and Levitskii [26] independently argued that the observed large energy spread anomalies are due to the modification and variation of the plasma potential by energetic electrons that have come under the influence of strong RF electric fields existing in the region between the plasma and the electrode, or between the plasma and the walls.…”