EP0165140B1 - Surface ionisation-type ion source, particularly for the realisation of an ionic probe - Google Patents

Surface ionisation-type ion source, particularly for the realisation of an ionic probe Download PDF

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Publication number
EP0165140B1
EP0165140B1 EP85400969A EP85400969A EP0165140B1 EP 0165140 B1 EP0165140 B1 EP 0165140B1 EP 85400969 A EP85400969 A EP 85400969A EP 85400969 A EP85400969 A EP 85400969A EP 0165140 B1 EP0165140 B1 EP 0165140B1
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Prior art keywords
ions
source according
ion source
active surface
ionization
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German (de)
French (fr)
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EP0165140A1 (en
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Georges Slodzian
Bernard Daigne
François Girard
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Office National dEtudes et de Recherches Aerospatiales ONERA
Universite Paris Sud Paris 11
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Office National dEtudes et de Recherches Aerospatiales ONERA
Universite Paris Sud Paris 11
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J27/00—Ion beam tubes
    • H01J27/02—Ion sources; Ion guns
    • H01J27/26—Ion sources; Ion guns using surface ionisation, e.g. field effect ion sources, thermionic ion sources

Definitions

  • the invention relates to ion sources operating by surface ionization.
  • Ion sources of this type are already known which include, under vacuum, a source of neutral particles of the same nature as the ions to be produced, an ionization support which has at least one active surface suitable for adsorption of the particles. neutrals, followed by their desorption in the form of ions, means for bringing the neutral particles to the ionization support, which transforms them into ions by adsorption / desorption, and means for channeling most of the ions thus produced in a beam emitted in a chosen direction of space.
  • the degree of ionization obtained during such a desorption is governed by the law of Saha-Langmuir. This law expresses an exponential dependence according to the difference between the work of exit of the heated support and the potential of ionization for positive ions or the electronic affinity for negative ions.
  • a suitable choice of the material of the ionization support makes it possible to obtain a probability of ionization close to unity.
  • the temperature of the support then has only a weak influence on the probability of ionization.
  • it plays a decisive role in the desorption process. In particular, it influences the residence time of an atom adsorbed on the surface of the support.
  • a hot surface which receives for example a jet of alkaline atoms such as potassium, rubidium or cesium, will have, in steady state, and in a situation of equilibrium where there is no accumulation, a cover (number of atoms adsorbed per unit area) which will depend on the incident flux of neutral atoms and the temperature of the support. But the presence of these adsorbed atoms then modifies the output work and can therefore influence the probability of ionization, in particular causing it to decrease sharply. It thus appears that the ion sources have a complex functioning.
  • dl is the intensity of the beam emitted by a surface element of in a solid angle dQ defined around a direction characterized by angles 0 and ⁇ , and in an energy band located between E and E + dE.
  • Gloss B is a function of 0, ⁇ and E.
  • Ion sources are already known in which the ionizing member is a sintered tungsten pellet.
  • An alkaline vapor passes through the interstices which remain between the tungsten grains and the pellet is brought to a temperature of the order of 1,200 ° C., while being placed in an electric field intended to accelerate the ions which emerge between the grains.
  • the source of neutral particles is a reservoir of liquid cesium, the temperature of which is adjusted to obtain a pressure of cesium vapor sufficient to force the diffusion of this vapor through the pores of the sintered tungsten pellet.
  • This first known source of ions has the particularity that the atoms to be ionized cross the ionization support.
  • This type of ion source makes it possible to reach high intensities, provided that a large emissive surface is used.
  • Sources of ions using a hot filament are also known. Their assembly is analogous to that of an electron gun: a filament, folded back in a hairpin, is placed in the center of a circular orifice pierced in an electrode which plays the role of screen and Wehnelt electrode. The filament and the Wehnelt are brought to high positive voltage and arranged in front of an electrode at the potential of the earth pierced with a circular hole (equivalent to the anode of an electron gun). The space between the filament and this "anode” is filled with cesium vapor produced by an annex furnace.
  • Ion sources are also known in which the ionization support is arranged in a baffle, which obstructs the passage of neutral particles in the beam of emitted ions.
  • United States patent 3,283,193 can, under certain reservations, be considered as also describing a baffle, in the rather special context of the catalytic production of nascent hydrogen.
  • Electronic bombardment ionizes part of the hydrogen atoms before they have had time to recombine into molecules.
  • the ion source thus produced is not very bright, wide, and fairly dispersed in energy. It is also not very stable, and vapors are released out of the ionizer itself, since few hydrogen atoms are actually ionized.
  • the ionization support is defined by thin conductive parts, all thin parts except one having a central hole and being stacked so that they internally form a cylindrical passage coaxial with the orifice of outlet, and of cross section smaller than that of said closed conduit;
  • the baffle is defined by the fact that said part without central hole is a plate pierced only with peripheral holes inside the passage, which it crosses, while its central part defines said active surface opposite the outlet orifice ; this achieves a quasi-perfect baffle preventing the direct passage of neutral particles in the emitted beam, without them having struck the active surface of the ionization support.
  • the ionization support is housed inside a conductive cap, mounted at the end of said conduit, which is completely closed by the cap except at the outlet orifice of the latter. .
  • the dimensions of the duct are adapted to preserve the chicane effect obtained in the ionization support.
  • the focusing means comprise an external focusing electrode, pierced and arranged to establish between the active surface and the outlet orifice, an electric field suitable for accelerating the ions to constitute the emission beam.
  • the potential difference between the active surface and the external electrode is of the order of at least 10 kilovolts, the size of the outlet orifice being a few tenths of a millimeter, and the latter being flared outwards.
  • the ion source comprises means suitable for heating the ionization support, preferably to a temperature of between 1000 and 1500 ° C.
  • the source of neutral particles may comprise a solid compound capable of delivering said particles by pyrolysis and, preferably, without gassing.
  • the active surface of the ionization support is curved, opposite the outlet orifice.
  • this ion source can function in particular with alkaline atoms, positively ionized, as well as with halogen atoms ionized negatively.
  • a particular arrangement of the active ionization surface makes it possible to obtain a beam which is as rich in ions on its periphery as in its center or, on the contrary, a beam whose ions are essentially concentrated in the emission axis. .
  • the source of neutral particles is designated by 1. It comprises a container consisting of a cylindrical side wall 11 and a bottom 12, integral with a sleeve 14 facing downward, and suitable for being housed on a support of alumina 15. Apart from this alumina support 15, all the parts of the ion source in FIGS. 1 and 2 are metallic.
  • the container 1 is surmounted by a bell 31 communicating with a tubular metal conduit 30 which defines means 3 for bringing neutral particles to the ionization support 2.
  • the bell 31 is screwed to the wall 11, with interposition of a copper gasket 19.
  • tank 1 a solid compound has been shown at 10, but which could be in the form of discrete particles, capable of producing by pyrolysis of vapors (ionized or not).
  • the corresponding neutral atoms can be produced by pyrolysis of a compound such as an alumino-silicate, an iodide, or a carbonate, for example.
  • alumino-silicate is particularly advantageous in that it leaves only solid residues and does not produce gas emissions.
  • the upper end of the tube 30 is provided with a cap 51, which closes it completely, except in an outlet orifice 50 which flares upwards in a flat V-shaped cross section.
  • the periphery of the cap extends axially over a substantial length of the tube 30.
  • a groove machined in the internal wall of the molybdenum cap 51 loqe a nickel seal 53 formed by electron bombardment to obtain a weld.
  • the whole of the ion source itself is brought for example to a potential of 10 kilovolts, which can be applied to the tube 30, or at the level of the reservoir 1 (FIG. 3).
  • a potential of 10 kilovolts which can be applied to the tube 30, or at the level of the reservoir 1 (FIG. 3).
  • an electrode 55 placed at the earth potential is placed. The structure of this electrode 55 will be described in more detail with reference to FIG. 3.
  • the cap 51, the orifice 50 and the electrode 55 define means 5 for focusing the ions produced in a beam which is emitted in a chosen direction of space.
  • ionization support generally designated by 2, and inserted between the cap 51 and the upper end of the tube 30.
  • This ionization support will now be described with reference to FIG. 2A. It comprises, bearing on the tube 30, a first annular washer 61, surmounted by a plate 62, pierced with four holes 65 to 68, then a second washer 63, which can be further surmounted by a last washer 64 , the assembly being held by the underside 25 of the top of the cap 51.
  • the surfaces 21 to 24 as well as 25 are also made of metallic material and, consequently, also capable of adsorption / desorption generating ions.
  • the ions thus created can again adsorb / desorb on the main active surface 20, or possibly exit through the orifice 50, at least for some of them.
  • the material cone of the cap 51 and which defines the orifice 50 here has an angle of 30 °. This leaves room for fairly inclined ion trajectories, at the start, with respect to the main direction of emission D of FIG. 2A.
  • the applied electric field which accelerates the ions in the direction D, of course bends this trajectory so that it returns thereafter on the axis.
  • the direct passage of neutral particles between the tube 30 and the orifice 50 could be made impossible by removing the washer 24, which, like the other stacked members 21 to 23, has a thickness of 0.1 mm. This further decreases the distance between surfaces 20 and 25.
  • the baffle is provided essentially by the fact that the plate 62 has four holes 65 to 68, off-center and drilled in a regularly distributed manner.
  • this embodiment is not limiting. A greater number of holes can be provided, possibly placed irregularly, provided that they are suitably off-center. It is also possible to make annular recesses in the plate 62, reserving the necessary fasteners for the maintenance of its central part 20.
  • the end of the tube 30, the cap 51, and the plate 62 (as well as the washers 61, 63 and 64) are heated to a temperature of between 1000 and 1500 °. C.
  • the tank 1 must for its part be heated to allow the pyrolysis of the compound which it contains. This heating can be independent of the previous one.
  • the heating is ensured by electronic bombardment by means of a filament F, supplied in an adjustable manner with electric current to be brought to the desired temperature.
  • a filament F supplied in an adjustable manner with electric current to be brought to the desired temperature.
  • Independent heating of the reservoir is not therefore essential, since the section and the length of the tube 30 can be provided so that the thermal leak occurring during the heating of the ionization support itself is sufficient to supply the reservoir 1 with l energy needed to bring the compound (alumino-silicate-cesium) it contains to an adequate temperature.
  • FIG. 3 shows a metal support 80 on which is mounted an alumina spacer 81, which in turn supports a metal electrode 82, protected by a heat shield 83.
  • the electrode 55 which here takes on an annular shape pierced with a central hole 58 for the passage of the ions produced. Slightly downstream of this hole 58, the electrode 55 supports a tantalum heat shield 56 pierced with a central hole. Still downstream, a fixing 59 of the grounded electrode 55 supports a lens shown diagrammatically at 90, and receiving a positive high voltage supply 95. Finally, on the bottom side, the electrode 55 is connected to an enclosure shown schematically in 89, isolating the ion source from the atmosphere, and making it possible to create a partial vacuum desirable for its operation.
  • the lens 80 is chosen according to the use for which the ion source is intended.
  • the lens 90 is used to create a real image of the virtual point source that constitutes the ion source of the invention.
  • the core of the probe consists of the cap 51, the baffle, which must be as thin as possible (distance between the surfaces 20 and 25), and the extraction electrode 55 whose role is to establish an electric field as large as possible at the surface 20 of the ionizer to ensure the extraction of ions.
  • a very strong extractor field makes it possible to obtain a high gloss without the need to increase the diameter of the orifice 50.
  • the electrode 55 is made of a material, such as Tantalum , emitting few negative ions due to the bombardment of positive ions in the beam. But this positive ion bombardment will create electrons which return to bomb the cap 51 at + 10 kV.
  • This parasitic phenomenon creates heating additional cap (and the entire ionizer). This increases the feed rate, and may make it impossible to control the temperature of the ionizer.
  • FIGS. 4 and 4A takes advantage of the parasitic phenomenon which has just been described.
  • an insulating insert 57A is placed supporting a ring electrode 57 whose internal, free edge is coaxial with the orifice 58;
  • the operation of the ion source is then started by heating the cap 51 using the filament F, as before. Then, the polarization of the additional electrode 57 is adjusted in order to focus the secondary electrons on the ionizing surface 20. It is then possible to stop the heating by the filament F, or decrease it for an auxiliary heating ensuring the compensation of the heat losses of the external walls of the ionizer assembly (organs 1 to 5).
  • the role of active surface of the ionizer is played essentially by surface 20. But this role can also be played, to a certain extent, by any surface of the same metal brought to a sufficient temperature, which is the case for the internal face 25 of the cap, and for the lateral surfaces 21 to 24, as previously indicated.
  • the ions thus produced laterally can go to the active surface 20, leave again in the same state (of ions) and then undergo the acceleration which will make them exit by the exit orifice 50, then by the hole 58 (FIG. 3) .
  • the emitted ion beam does not have a substantially Gaussian distribution centered on its main direction D, but on the contrary a fairly wide, rather reinforced, distribution on a peripheral ring of this beam;
  • any reduction in beam size by this means produces an increase in the aperture angle and therefore an increase in aperture aberrations, which defeats the purpose, at know how to produce a small probe.
  • This effect makes it necessary to reduce the opening angle, by interposing suitably arranged diaphragms. Under these conditions, as the ions coming from the abovementioned circular crown do not feed the smallest opening angles, they are not useful for the creation of an ion probe.
  • the invention provides (FIG. 2C) that a thin disc of lanthanum hexaboride, denoted 64A, is placed on the internal face 25 of the cap and pierced with a central hole substantially the same size as the orifice 50.
  • the disk 64A can be replaced by a deposit of lanthanum hexaboride produced by vacuum evaporation. The thickness being less, the electric field of extraction is increased.
  • lanthanum hexaboride has a lower output work than the ionization energy of cesium (for example).
  • cesium for example
  • the cesium atoms which have struck the lanthanum hexaboride disc leave in the form of neutral atoms, and then strike the actie surface 20A, which is the only ionizing surface.
  • the ion beam thus obtained is then particularly suitable for producing an ion probe.
  • the source of the invention also allows the production of negative ions, by of course passing the voltage between the ionizer and the electrode 55 to -10 kilovolts.
  • the additional electrode 57 polarized at + 320 V, is used to block positive ions.
  • FIG. 2A has a metal surface 25 and a surface 20 in lanthanum hexaboride.
  • an ion beam starting from the surface 20 will then be produced.
  • This ion beam is of the very point type suitable for ion probes.
  • iodine crystals are placed in the tank, which produce iodine vapor by gentle heating. Iodine atoms do not ionize on metal, whereas they will ionize on lanthanum hexaboride.
  • negative ions can be created from halogens, namely not only iodine, but also chlorine for example. It is also conceivable to produce negative ions from alkaline atoms, although their interest is then more limited.
  • the probability of ionization for positive ions is high when the material of the active surface has, for these ions, an output work greater than their ionization potential.
  • the material of the active surface has, for these ions, an output work lower than their electronic affinity.
  • the geometry of the orifice 50 is not necessarily circular. This geometry may depend on the shape of the ion beam which is desired for working downstream.

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Description

L'invention concerne les sources d'ions opérant par ionisation de surface.The invention relates to ion sources operating by surface ionization.

On connaît déjà des sources d'ions de ce type qui comprennent, sous vide, une source de particules neutres de même nature que les ions à produire, un support d'ionisation qui possède au moins une surface active propre à l'adsorption des particules neutres, suivie de leur désorption sous forme d'ions, des moyens pour amener les particules neutres vers le support d'ionisation, lequel les transforme en ions par adsorption/ désorption, et des moyens de canaliser la plus grande partie des ions ainsi produits en un faisceau émis dans une direction choisie de l'espace.Ion sources of this type are already known which include, under vacuum, a source of neutral particles of the same nature as the ions to be produced, an ionization support which has at least one active surface suitable for adsorption of the particles. neutrals, followed by their desorption in the form of ions, means for bringing the neutral particles to the ionization support, which transforms them into ions by adsorption / desorption, and means for channeling most of the ions thus produced in a beam emitted in a chosen direction of space.

Il est connu depuis longtemps qu'un atome peut désorber d'une surface chaude à l'état d'ion positif ou négatif. Les principaux paramètres qui régissent ce phénomène sont, d'une part, la température du support d'ionisation et le travail de sortie électronique, d'autre part la propension à l'ionisation de l'élément qui désorbe. Cette propension s'exprime par le potentiel d'ionisation ou par l'affinité électronique, suivant qu'il s'agit d'ionisation positive ou négative.It has long been known that an atom can desorb from a hot surface as a positive or negative ion. The main parameters which govern this phenomenon are, on the one hand, the temperature of the ionization support and the work of electronic output, on the other hand the propensity to ionization of the element which desorbs. This propensity is expressed by the ionization potential or by electronic affinity, depending on whether it is positive or negative ionization.

Le degré d'ionisation obtenu lors d'une telle désorption est régi par la loi de Saha-Langmuir. Cette loi exprime une dépendance exponentielle en fonction de la différence entre le travail de sortie du support chauffé et le potentiel d'ionisation pour des ions positifs ou l'affinité électronique pour des ions négatifs.The degree of ionization obtained during such a desorption is governed by the law of Saha-Langmuir. This law expresses an exponential dependence according to the difference between the work of exit of the heated support and the potential of ionization for positive ions or the electronic affinity for negative ions.

Pour des ions à produire déterminés, un choix convenable du matériau du support d'ionisation permet d'obtenir une probabilité d'ionisation voisine de l'unité. La température du support n'a alors qu'une influence faible sur la probabilité d'ionisation. Par contre, elle intervient de façon déterminante dans le processus de désorption. En particulier, elle influe sur le temps de séjour d'un atome adsorbé à la surface du support.For determined ions to be produced, a suitable choice of the material of the ionization support makes it possible to obtain a probability of ionization close to unity. The temperature of the support then has only a weak influence on the probability of ionization. On the other hand, it plays a decisive role in the desorption process. In particular, it influences the residence time of an atom adsorbed on the surface of the support.

Ainsi, une surface chaude qui reçoit par exemple un jet d'atomes alcalins tels que du potassium, du rubidium ou du césium, aura, en régime permanent, et dans une situation d'équilibre où il n'y a pas d'accumulation, une couverture (nombre d'atomes adsorbés par unité d'aire) qui dépendra du flux incident d'atomes neutres et de la température du support. Mais la présence de ces atomes adsorbés modifie alors le travail de sortie et peut donc influer sur la probabilité d'ionisation, en particulier la faire décroître fortement. Il apparaît ainsi que les sources d'ions possèdent un fonctionnement complexe.Thus, a hot surface which receives for example a jet of alkaline atoms such as potassium, rubidium or cesium, will have, in steady state, and in a situation of equilibrium where there is no accumulation, a cover (number of atoms adsorbed per unit area) which will depend on the incident flux of neutral atoms and the temperature of the support. But the presence of these adsorbed atoms then modifies the output work and can therefore influence the probability of ionization, in particular causing it to decrease sharply. It thus appears that the ion sources have a complex functioning.

L'une des qualités principales des sources d'ions est leur brillance, qui peut être définie par l'expression:

  • dl = B.ds.dQ.dE
One of the main qualities of ion sources is their brightness, which can be defined by the expression:
  • dl = B.ds.dQ.dE

où dl est l'intensité du faisceau émis par un élément de surface de dans un angle solide dQ défini autour d'une direction caractérisée par des angles 0 et Φ, et dans une bande énergétique située entre E et E+dE. La brillance B est une fonction de 0, Φ et E.where dl is the intensity of the beam emitted by a surface element of in a solid angle dQ defined around a direction characterized by angles 0 and Φ, and in an energy band located between E and E + dE. Gloss B is a function of 0, Φ and E.

Dans un exemple simplifié, on considère une surface plane émissive parallèle à une électrode plane percée d'un trou rond. Une tension V positive ou négative est établie entre la surface émissive et l'électrode placée au potentiel de la terre. On admet que B est indépendant de l'angle azimutaI Φ et que sa dépendance en fonction de 0, angle de la direction d'émission avec la normale, suit une loi de Lambert en cosinus 0. La brillance B s'écrit alors:

Figure imgb0001

  • où Eo est l'énergie initiale de la particule qui quitte la surface et Jo la densité du courant (intensité par unité de surface) des particules au niveau de la surface émissive. On remarque sur cet exemple que les sources d'ions thermiques fournissent une faible valeur de l'énergie initiale Eo de l'ion quittant la surface. On note également l'importance de la fonction d'apport (qui définit le flux incident de particules neutres), puisque cette fonction d'apport contrôle la densité de courant Jo.
In a simplified example, we consider an emissive planar surface parallel to a planar electrode pierced with a round hole. A positive or negative voltage V is established between the emissive surface and the electrode placed at the earth potential. We admit that B is independent of the angle azimutaI Φ and that its dependence as a function of 0, angle of the direction of emission with the normal, follows a Lambert law in cosine 0. The brightness B is then written:
Figure imgb0001
  • where E o is the initial energy of the particle leaving the surface and J o the current density (intensity per unit area) of the particles at the emissive surface. It is noted in this example that the sources of thermal ions provide a low value of the initial energy E o of the ion leaving the surface. We also note the importance of the input function (which defines the incident flow of neutral particles), since this input function controls the current density Jo.

On connaît déjà des sources d'ions dans lesquelles l'organe ioniseur estune pastille de tungstène fritté. Une vapeur alcaline passe dans les interstices qui demeurent entre les grains de tungstène et la pastille est portée à une température de l'ordre de 1 200°C, tout en se trouvant placée dans un champ électrique destiné à accélérer les ions qui émergent entre les grains. La source de particules neutres est un réservoir de césium liquide, dont la température est ajustée pour obtenir une pression de vapeur de césium suffisante pour forcer la diffusion de cette vapeur à travers les pores de la pastille de tungstène fritté. En effet, cette première source d'ions connue présente la particularité que les atomes à ioniser traversent le support d'ionisation.Ion sources are already known in which the ionizing member is a sintered tungsten pellet. An alkaline vapor passes through the interstices which remain between the tungsten grains and the pellet is brought to a temperature of the order of 1,200 ° C., while being placed in an electric field intended to accelerate the ions which emerge between the grains. The source of neutral particles is a reservoir of liquid cesium, the temperature of which is adjusted to obtain a pressure of cesium vapor sufficient to force the diffusion of this vapor through the pores of the sintered tungsten pellet. This first known source of ions has the particularity that the atoms to be ionized cross the ionization support.

Ce type de source d'ions permet d'atteindre des intensités élevées, sous réserve d'utiliser une grande surface émissive.This type of ion source makes it possible to reach high intensities, provided that a large emissive surface is used.

Cela en limite considérablement l'intérêt lorsque l'on veut produire une sonde ionique, c'est-à-dire une source d'ions fournissant un pinceau fin. En effet, il est a priori difficile de rendre petite la surface émissive, et il faut donc partir d'une surface relativement grande, dont une grande partie des ions qu'elle produit sont par la suite éliminés par des diaphragmes.This considerably limits its advantage when one wants to produce an ion probe, that is to say a source of ions providing a fine brush. Indeed, it is a priori difficult to make the emissive surface small, and it is therefore necessary to start from a relatively large surface, a large part of the ions which it produces are subsequently eliminated by diaphragms.

On connaît aussi des sources d'ions utilisant un filament chaud. Leur montage est analogue à celui d'un canon à électrons: un filament, replié en épingle à cheveux, est placé au centre d'un orifice circulaire percé dans une électrode qui joue le rôle d'écran et d'électrode de Wehnelt. Le filament et le Wehnelt sont portés à la haute tension positive et disposés en face d'une électrode au potentiel de la terre percée d'un trou circulaire (équivalent de l'anode d'un canon à électrons). L'espace entre le filament et cette "anode" est rempli par la vapeur de césium produite par un four annexe. Les atomes de césium qui s'ionisent sur la pointe du filament sont accélérés par le champ électrique et sortent par le trou de l'"anode", en semblant provenir d'une source virtuelle de petite dimension. Ce montage connu permet déjà d'obtenir une source suffisamment ponctuelle pour la réalisation d'une sonde ionique. Il présente cependant deux inconvénients majeurs: le premier est qu'au-delà de 5 kV, les claquages deviennent fréquents, pour des raisons difficiles à contrôler telles que la métallisation des isolants et des émissions électroniques parasites, et le second inconvénient est que la vapeur de césium s'échappe par le trou de sortie, et se condense dans d'autres parties de l'installation.Sources of ions using a hot filament are also known. Their assembly is analogous to that of an electron gun: a filament, folded back in a hairpin, is placed in the center of a circular orifice pierced in an electrode which plays the role of screen and Wehnelt electrode. The filament and the Wehnelt are brought to high positive voltage and arranged in front of an electrode at the potential of the earth pierced with a circular hole (equivalent to the anode of an electron gun). The space between the filament and this "anode" is filled with cesium vapor produced by an annex furnace. The cesium atoms which ionize on the tip of the filament are accelerated by the electric field and exit through the hole in the "anode", seeming to come from a small virtual source. This known arrangement already makes it possible to obtain a source which is sufficiently punctual for the production of an ion probe. However, it has two major drawbacks: the first is that beyond 5 kV, breakdowns become frequent, for reasons difficult to control such as the metallization of insulators and parasitic electronic emissions, and the second drawback is that steam of cesium escapes through the outlet hole, and condenses in other parts of the installation.

On connaît encore des sources d'ions dans lesquelles le support d'ionisation est agencé en une chicane, qui fait obstacle au passage des particules neutres dans le faisceau d'ions émis.Ion sources are also known in which the ionization support is arranged in a baffle, which obstructs the passage of neutral particles in the beam of emitted ions.

C'est le cas du certificat d'addition français N° 65 999 qui concerne un tube à décharge. La chicane, très simple opère à la condition que les atomes neutres se propagent en ligne droite. Mais la source d'ions de ce document antérieur est peu brillante, sujette à dispersion énergétique élevée, et de dimensions assez grandes. De plus il est estimé qu'elle est peu stable, et que des vapeurs vont se répandre à l'intérieur du tube à décharge, ce qui est admissible pour un tel tube.This is the case of the French addition certificate N ° 65,999 which relates to a discharge tube. The very simple chicane operates on the condition that the neutral atoms propagate in a straight line. However, the ion source of this prior document is not very bright, subject to high energy dispersion, and of fairly large dimensions. In addition, it is estimated that it is not very stable, and that vapors will spread inside the discharge tube, which is admissible for such a tube.

Le brevet Etats-Unis 3 283 193 peut, sous certaines réserves, être considéré comme décrivant éqalement une chicane, dans le contexte assez spécial de la production catalytique d'hydrogène naissant. Un bombardement électronique ionise une partie des atomes d'hydrogène avant qu'ils n'aient eu le temps de se recombiner en molécules. Là encore, il est clair que la source d'ions ainsi produite est peu brillante, large, et assez dispersée en énergie. Elle est aussi peu stable, et des vapeurs sont libérées hors de l'ioniseur lui-même, car peu d'atomes d'hydrogène sont effectivement ionisés.United States patent 3,283,193 can, under certain reservations, be considered as also describing a baffle, in the rather special context of the catalytic production of nascent hydrogen. Electronic bombardment ionizes part of the hydrogen atoms before they have had time to recombine into molecules. Again, it is clear that the ion source thus produced is not very bright, wide, and fairly dispersed in energy. It is also not very stable, and vapors are released out of the ionizer itself, since few hydrogen atoms are actually ionized.

Dans ces conditions, la présente invention vient fournir une nouvelle source d'ions qui offre, par rapport aux sources d'ions antérieurement connues, des avantages manifestes et en particulier les suivants:

  • - surface émissive de très faible dimension, à très grande brillance lorsque l'application le veut;
  • - absence de flux direct d'atomes ou particules neutres dans le reste de l'installation;
  • - utilisation d'une tension d'accélération supérieure à une dizaine de kilovolts sans provoquer de claquages;
  • - utilisation d'une source solide de particules neutres fonctionnant sous faible pression, évitant le recours à un métal liquide;
  • - faisceau d'ions stable et de faible dispersion énergétique;
  • - faisceau d'ions dont la géométrie est bien maitrisée, ce qui permet d'éviter l'érosion des électrodes par pulvérisation cathodique.
  • L'invention part d'une source d'ions opérant par ionisation de surface, du type comprenant, sous vide,
  • - une source de particules neutres, de même nature que les ions à produire,
  • - des moyens définissant avec cette source un conduit fermé sauf en un orifice d'extrémité situé à l'opposé de ladite source,
  • - un support d'ionisation, qui possède en regard de l'orifice une surface active propre à t'adsorption des particules neutres, suivie de leur désorption sous forme d'ions, ce support d'ionisation étant arrangé dans le conduit fermé et formant une chicane qui fait obstacle au passage des particules neutres dans le faisceau d'ions émis, et
  • - des moyens de focaliser les ions ainsi produits à travers l'orifice en un faisceau émis dans une direction choisie de l'espace.
Under these conditions, the present invention provides a new ion source which offers, compared to previously known ion sources, obvious advantages and in particular the following:
  • - very small emissive surface, with very high gloss when the application requires it;
  • - absence of direct flow of neutral atoms or particles in the rest of the installation;
  • - use of an acceleration voltage greater than ten kilovolts without causing breakdowns;
  • - use of a solid source of neutral particles operating under low pressure, avoiding the use of a liquid metal;
  • - stable ion beam with low energy dispersion;
  • - ion beam whose geometry is well controlled, which prevents erosion of the electrodes by sputtering.
  • The invention starts from a source of ions operating by surface ionization, of the type comprising, under vacuum,
  • - a source of neutral particles, of the same nature as the ions to be produced,
  • - means defining with this source a closed conduit except at an end orifice situated opposite said source,
  • an ionization support, which has an active surface facing the orifice suitable for adsorption of neutral particles, followed by their desorption in the form of ions, this ionization support being arranged in the closed conduit and forming a baffle which obstructs the passage of neutral particles in the beam of emitted ions, and
  • - Means for focusing the ions thus produced through the orifice in a beam emitted in a chosen direction of space.

Selon une première caractéristique de l'invention, le support d'ionisation est défini par des pièces minces conductrices, toutes pièces minces sauf une ayant un trou central et étant empilées de sorte qu'elles forment intérieurement un passage cylindrique coaxial à l'orifice de sortie, et de section droite inférieure à celle dudit conduit fermé; la chicane est définie par le fait que ladite pièce sans trou central est une plaque percée seulement de trous périphériques à l'intérieur du passage, qu'elle traverse, tandis que sa partie centrale définit ladite surface active en regard de l'orifice de sortie; ceci réalise une chicane quasi-parfaite empêchant le passage direct des particules neutres dans le faisceau émis, sans qu'elles n'aient frappé la surface active du support d'ionisation.According to a first characteristic of the invention, the ionization support is defined by thin conductive parts, all thin parts except one having a central hole and being stacked so that they internally form a cylindrical passage coaxial with the orifice of outlet, and of cross section smaller than that of said closed conduit; the baffle is defined by the fact that said part without central hole is a plate pierced only with peripheral holes inside the passage, which it crosses, while its central part defines said active surface opposite the outlet orifice ; this achieves a quasi-perfect baffle preventing the direct passage of neutral particles in the emitted beam, without them having struck the active surface of the ionization support.

Selon un autre aspect de l'invention, le support d'ionisation est logé à l'intérieur d'un capuchon conducteur, monté en bout dudit conduit, lequel est fermé complètement par le capuchon sauf en l'orifice de sortie de celui-ci. Les dimensions du conduit sont adaptées pour conserver l'effet de chicane obtenu dans le support d'ionisation.According to another aspect of the invention, the ionization support is housed inside a conductive cap, mounted at the end of said conduit, which is completely closed by the cap except at the outlet orifice of the latter. . The dimensions of the duct are adapted to preserve the chicane effect obtained in the ionization support.

Très avantageusement, les moyens de focalisation comprennent une électrode externe de focalisation, percée et agencée pour établir entre la surface active et l'orifice de sortie, un champ électrique propre à accélérer les ions pour constituer le faisceau d'émission.Very advantageously, the focusing means comprise an external focusing electrode, pierced and arranged to establish between the active surface and the outlet orifice, an electric field suitable for accelerating the ions to constitute the emission beam.

Selon encore un autre aspect de l'invention, la différence de potentiel entre la surface active et l'électrode externe est de l'ordre de 10 kilovolts au moins, la taille de l'orifice de sortie étant de quelques dixièmes de millimètres, et celui-ci étant évasé vers l'extérieur.According to yet another aspect of the invention, the potential difference between the active surface and the external electrode is of the order of at least 10 kilovolts, the size of the outlet orifice being a few tenths of a millimeter, and the latter being flared outwards.

De préférence, la source d'ions comporte des moyens propres à chauffer le support d'ionisation, de préférence à une température comprise entre 1 000 et 1 500° C.Preferably, the ion source comprises means suitable for heating the ionization support, preferably to a temperature of between 1000 and 1500 ° C.

Dans ces conditions, la source de particules neutres peut comprendre un composé solide propre à délivrer lesdites particules par pyrolyse et, de préférence, sans dégagement gazeux.Under these conditions, the source of neutral particles may comprise a solid compound capable of delivering said particles by pyrolysis and, preferably, without gassing.

Selon un autre aspect encore de l'invention, la surface active du support d'ionisation est bombée, en regard de l'orifice de sortie.According to yet another aspect of the invention, the active surface of the ionization support is curved, opposite the outlet orifice.

Comme on le verra plus loin, cette source d'ions peut fonctionner notamment avec des atomes alcalins, ionisés positivement, ainsi qu"avec des atomes d'halogène ionisés négativement.As will be seen below, this ion source can function in particular with alkaline atoms, positively ionized, as well as with halogen atoms ionized negatively.

Un aménagement particulier de la surface active d'ionisation permet d'obtenir un faisceau qui est aussi riche en ions sur sa périphérie qu'en son centre ou, au contraire, un faisceau dont les ions sont essentiellement concentrés dans l'axe d'émission.A particular arrangement of the active ionization surface makes it possible to obtain a beam which is as rich in ions on its periphery as in its center or, on the contrary, a beam whose ions are essentially concentrated in the emission axis. .

D'autres caractéristiques et avantages de l'invention apparaîtront à l'examen de la description détaillée qui va suivre, et des dessins annexés, sur lesquels:

  • - la figure 1 est une vue en coupe verticale de la partie principale de la source d'ions selon l'invention;
  • - la figure 2A est un détail de la partie supérieure de la figure 1;
  • - la figure 2B est une vue de dessous du détail de la figure 2A;
  • - la figure 2C est une vue correspondant à la figure 2A et montrant une variante de réalisation de l'invention;
  • - la figure 3 illustre de manière plus complète une source d'ions selon la présente invention; et
  • - les figures 4 et 4A illustrent une variante préférentielle de la source d'ions selon l'invention.
Other characteristics and advantages of the invention will appear on examining the detailed description which follows, and the appended drawings, in which:
  • - Figure 1 is a vertical sectional view of the main part of the ion source according to the invention;
  • - Figure 2A is a detail of the upper part of Figure 1;
  • - Figure 2B is a bottom view of the detail of Figure 2A;
  • - Figure 2C is a view corresponding to Figure 2A and showing an alternative embodiment of the invention;
  • - Figure 3 illustrates more fully an ion source according to the present invention; and
  • - Figures 4 and 4A illustrate a preferred variant of the ion source according to the invention.

La géométrie de la source d'ions selon l'invention est essentielle. En conséquence, les dessins annexés font partie intégrante de la présente description, et pourront contribuer à la suffisance de celle-ci, ainsi qu'à la définition de l'invention.The geometry of the ion source according to the invention is essential. Consequently, the appended drawings form an integral part of this description, and may contribute to the sufficiency thereof, as well as to the definition of the invention.

La source de particules neutres est désignée par 1. Elle comporte un récipient constitué d'une paroi latérale cylindrique 11 et d'un fond 12, solidaire d'un manchon 14 tourné vers le bas, et propre à se loger sur un support d'alumine 15. En dehors de ce support d'alumine 15, toutes les parties de la source d'ions sur les figures 1 et 2 sont métalliques.The source of neutral particles is designated by 1. It comprises a container consisting of a cylindrical side wall 11 and a bottom 12, integral with a sleeve 14 facing downward, and suitable for being housed on a support of alumina 15. Apart from this alumina support 15, all the parts of the ion source in FIGS. 1 and 2 are metallic.

Le récipient 1 est surmonté d'une cloche 31 communiquant avec un conduit métallique tubulaire 30 qui définit des moyens d'amenée 3 des particules neutres vers le support d'ionisation 2. La cloche 31 est vissée sur la paroi 11, avec interposition d'un joint en cuivre 19.The container 1 is surmounted by a bell 31 communicating with a tubular metal conduit 30 which defines means 3 for bringing neutral particles to the ionization support 2. The bell 31 is screwed to the wall 11, with interposition of a copper gasket 19.

Dans le réservoir 1, on a représenté en 10 un composé solide sous forme compacte mais qui pourrait être sous la forme de particules discrètes, propre à produire par pyrolyse des vapeurs (ionisées ou non).In tank 1, a solid compound has been shown at 10, but which could be in the form of discrete particles, capable of producing by pyrolysis of vapors (ionized or not).

On considérera tout d'abord les ions alcalins positifs tels gue les ions de césium, rubidium ou potassium. Ces ions sont intéressants car leur potentiel d'ionisation est plus petit que le travail de sortie de la plupart des métaux. Comme précédemment indiqué, la probabilité d'ionisation positive par désorption est alors voisine de l'unité.We will first consider positive alkaline ions such as cesium, rubidium or potassium ions. These ions are interesting because their ionization potential is smaller than the output work of most metals. As previously indicated, the probability of positive ionization by desorption is then close to unity.

Les atomes neutres correspondants (accompagnés éventuellement d'ions) peuvent être produits par pyrolyse d'un composé tel qu'un alumino-silicate, un iodure, ou un carbonate, par exemple. L'alumino-silicate est particulièrement avantageux en ce qu'il ne laisse que des résidus solides et ne produit pas de dégagements gazeux.The corresponding neutral atoms (possibly accompanied by ions) can be produced by pyrolysis of a compound such as an alumino-silicate, an iodide, or a carbonate, for example. The alumino-silicate is particularly advantageous in that it leaves only solid residues and does not produce gas emissions.

L'extrémité supérieure du tube 30 est munie d'un capuchon 51, qui la ferme complètement, sauf en un orifice de sortie 50 qui s'évase vers le haut selon une section droite en V aplati. La périphérie du capuchon s'étend axialement sur une longueur substantielle du tube 30. Une gorge usinée dans la paroi interne du capuchon en molybdène 51 loqe un joint de nickel 53 formé par bombardement électronique pour obtenir une soudure.The upper end of the tube 30 is provided with a cap 51, which closes it completely, except in an outlet orifice 50 which flares upwards in a flat V-shaped cross section. The periphery of the cap extends axially over a substantial length of the tube 30. A groove machined in the internal wall of the molybdenum cap 51 loqe a nickel seal 53 formed by electron bombardment to obtain a weld.

L'ensemble de la source d'ions elle-même est portée par exemple à un potentiel de 10 kilovolts, qui peut être appliqué au tube 30, ou au niveau du réservoir 1 (figure 3). En regard de l'ouverture 50 est placée une électrode 55 mise au potentiel de la terre. La structure de cette électrode 55 sera décrite plus en détail en référence à la figure 3.The whole of the ion source itself is brought for example to a potential of 10 kilovolts, which can be applied to the tube 30, or at the level of the reservoir 1 (FIG. 3). Opposite the opening 50, an electrode 55 placed at the earth potential is placed. The structure of this electrode 55 will be described in more detail with reference to FIG. 3.

Ensemble, le capuchon 51, l'orifice 50 et l'électrode 55 définissent des moyens 5 de focaliser les ions produits en un faisceau qui est émis dans une direction choisie de l'espace.Together, the cap 51, the orifice 50 and the electrode 55 define means 5 for focusing the ions produced in a beam which is emitted in a chosen direction of space.

La production même de ces ions est faite par un support d'ionisation désigné globalement par 2, et inséré entre le capuchon 51 et l'extrémité supérieure du tube 30. Ce support d'ionisation sera maintenant décrit en référence à la figure 2A. Il comporte, en appui sur le tube 30, une première rondelle annulaire 61, surmontée d'une plaque 62, percée de quatre trous 65 à 68, puis d'une deuxième rondelle 63, laquelle peut être encore surmontée d'une dernière rondelle 64, l'ensemble étant maintenu par la face inférieure 25 du dessus du capuchon 51.The actual production of these ions is done by an ionization support generally designated by 2, and inserted between the cap 51 and the upper end of the tube 30. This ionization support will now be described with reference to FIG. 2A. It comprises, bearing on the tube 30, a first annular washer 61, surmounted by a plate 62, pierced with four holes 65 to 68, then a second washer 63, which can be further surmounted by a last washer 64 , the assembly being held by the underside 25 of the top of the cap 51.

Il a été observé par les inventeurs qu'en jouant sur la distance entre la plaque 82, et la face interne 25 du capuchon, le diamètre de l'orifice 50, celui des trous 65 à 68, et le diamètre du cercle sur lequel se place l'axe de perçage de chacun de ces trous, on peut réaliser une chicane 8 quasi-parfaite, telle que les atomes d'alcalin issus du réservoir 1 ne puissent sortir de la source d'ions qu'après avoir frappé la surface 20 de la plaque 62 qui se trouve en reqard de l'orifice de sortie 50. Ceci concerne du moins la très grande majorité des atomes ou particules neutres produits par la source 1.It has been observed by the inventors that by varying the distance between the plate 82 and the internal face 25 of the cap, the diameter of the orifice 50, that of the holes 65 to 68, and the diameter of the circle on which is located. place the drilling axis of each of these holes, we can achieve a baffle 8 almost perfect, such that the alkali atoms from the tank 1 can not leave the ion source until after striking the surface 20 of the plate 62 which is located in relation to the outlet orifice 50. This at least concerns the very great majority of neutral atoms or particles produced by the source 1.

Comme précédemment indiqué, les phénomènes qui intervienennt sont complexes, et n'ont pu être entièrement expliqués à l'heure actuelle. Il semble que l'obtention d'une bonne chicane soit liée aux caractéristiques suivantes:

  • - Il n'y a pas (ou très peu) de possibilités de passaqe direct des atomes neutres depuis le conduit 30 jusgu'à l'ouverture 50.
  • - La chicane 6 est délimitée latéralement par les parois internes circulaires 21 à 24; elle est délimitée à son extrémité par la face radiale interne 25 du capuchon. Un atome neutre devra nécessairement subir un ou plusieurs chocs sur ces parois avant de rencontrer la surface active 20 qui assure, pour l'essentiel, l'émission ionigue à travers l'orifice 50.
  • - La distance entre la surface 20 et la face 25 est rendue aussi faible que possible.
As previously indicated, the phenomena which occur are complex, and have not been fully explained at present. It seems that obtaining a good chicane is linked to the following characteristics:
  • - There are no (or very few) possibilities for direct passage of neutral atoms from the conduit 30 to the opening 50.
  • - The baffle 6 is delimited laterally by the circular internal walls 21 to 24; it is delimited at its end by the radial face internal 25 of the cap. A neutral atom will necessarily have to undergo one or more shocks on these walls before meeting the active surface 20 which essentially provides ionic emission through the orifice 50.
  • - The distance between the surface 20 and the face 25 is made as small as possible.

Intervient encore le libre parcours moyen des atomes neutres de la vapeur utilisée, ici une vapeur de césium. La relation entre ce libre parcours moyen qui est en principe assez grand, et la taille du conduit 30 ainsi que des éléments de la chicane proprement dite n'a encore pu être établie.There is also the mean free path of the neutral atoms of the vapor used, here a cesium vapor. The relationship between this mean free path, which is in principle quite large, and the size of the conduit 30 as well as the elements of the baffle itself has not yet been established.

On remarque d'ailleurs que les surfaces 21 à 24 ainsi que 25 sont également réalisées en matériau métallique et, par conséquent, susceptibles, elles aussi, d'une adsorption/ désorption génératrice d'ions. Les ions ainsi créés peuvent à nouveau s'adsorber/désorber sur la surface active principale 20, ou éventuellement sortir par l'orifice 50, du moins pour certains d'entre eux. Le cône de matière du capuchon 51 et qui définit l'orifice 50, possède ici un angle de 30°. Ceci laisse la place à des trajectoires ioniques assez inclinées, au départ, par rapport à la direction principale d'émission D de la figure 2A. Le champ électrique appliqué, qui accélère les ions dans la direction D, infléchit bien sûr cette trajectoire pour qu'elle revienne par la suite sur l'axe.It should also be noted that the surfaces 21 to 24 as well as 25 are also made of metallic material and, consequently, also capable of adsorption / desorption generating ions. The ions thus created can again adsorb / desorb on the main active surface 20, or possibly exit through the orifice 50, at least for some of them. The material cone of the cap 51 and which defines the orifice 50, here has an angle of 30 °. This leaves room for fairly inclined ion trajectories, at the start, with respect to the main direction of emission D of FIG. 2A. The applied electric field, which accelerates the ions in the direction D, of course bends this trajectory so that it returns thereafter on the axis.

Par ailleurs, on note que le passage direct de particules neutres entre le tube 30 et l'orifice 50 pourrait être rendu impossible par suppression de la rondelle 24, qui, comme les autres organes empilés 21 à 23, possède une épaisseur de 0,1 mm. Ceci diminue encore la distance entre les surfaces 20 et 25.Furthermore, it is noted that the direct passage of neutral particles between the tube 30 and the orifice 50 could be made impossible by removing the washer 24, which, like the other stacked members 21 to 23, has a thickness of 0.1 mm. This further decreases the distance between surfaces 20 and 25.

Dans le mode de réalisation décrit, la chicane est fournie essentiellement par le fait que la plaque 62 possède quatre trous 65 à 68, décentrés et percés de manière régulièrement répartie. Bien entendu, cette réalisation n'est pas limitative. On peut prévoir un plus grand nombre de trous, éventuellement placés de manière irrégulière, pourvu qu'ils soient convenablement décentrés. On peut encore faire des évidements annulaires dans la plaquette 62, en réservant des attaches nécessaires pour le maintien de sa partie centrale 20.In the embodiment described, the baffle is provided essentially by the fact that the plate 62 has four holes 65 to 68, off-center and drilled in a regularly distributed manner. Of course, this embodiment is not limiting. A greater number of holes can be provided, possibly placed irregularly, provided that they are suitably off-center. It is also possible to make annular recesses in the plate 62, reserving the necessary fasteners for the maintenance of its central part 20.

Pour la plupart des applications, il est nécessaire que l'extrémité du tube 30, le capuchon 51, et la plaque 62 (de même que les rondelles 61, 63 et 64) soient chauffés à une température comprise entre 1 000 et 1 500° C. Le réservoir 1 doit pour sa part être chauffé pour permettre la pyrolyse du composé qu'il contient. Ce chauffage peut être indépendant du précédent.For most applications, it is necessary that the end of the tube 30, the cap 51, and the plate 62 (as well as the washers 61, 63 and 64) are heated to a temperature of between 1000 and 1500 °. C. The tank 1 must for its part be heated to allow the pyrolysis of the compound which it contains. This heating can be independent of the previous one.

Dans le mode de réalisation illustré (figure 3), le chauffage est assuré par bombardement électronique au moyen d'un filament F, alimenté de manière réglable en courant électrique pour être porté à la température voulue. Un chauffage indépendant du réservoir n'est alors pas indispensable, car la section et la longueur du tube 30 peuvent être prévues de manière que la fuite thermique intervenant lors du chauffage du support d'ionisation lui-même suffise à alimenter le réservoir 1 avec l'énergie nécessaire-pour porter le composé (alumino-silicate-de césium) qu'il contient à une température adéquate.In the illustrated embodiment (FIG. 3), the heating is ensured by electronic bombardment by means of a filament F, supplied in an adjustable manner with electric current to be brought to the desired temperature. Independent heating of the reservoir is not therefore essential, since the section and the length of the tube 30 can be provided so that the thermal leak occurring during the heating of the ionization support itself is sufficient to supply the reservoir 1 with l energy needed to bring the compound (alumino-silicate-cesium) it contains to an adequate temperature.

Il est maintenant fait référence à la figure 3. Celle-ci fait apparaître un support métallique 80 sur lequel est montée une entretoise d'alumine 81, qui soutient à son tour une électrode métallique 82, protégée par un écran thermique 83.Reference is now made to FIG. 3. This shows a metal support 80 on which is mounted an alumina spacer 81, which in turn supports a metal electrode 82, protected by a heat shield 83.

On reconnaît au centre les éléments 14, 15, 1, 3 et 51 de la source d'ions proprement dite. On distingue autour le filament F et son alimentation par une liaison électrique 86 traversant l'alumine 81.We recognize in the center the elements 14, 15, 1, 3 and 51 of the ion source itself. A distinction is made around filament F and its supply by an electrical connection 86 passing through alumina 81.

Au-dessus de la source d'ions est placée l'électrode 55, qui revêt ici une forme annulaire percée d'un trou central 58 pour le passage des ions produits. Légèrement en aval de ce trou 58, l'électrode 55 supporte un écran thermique de tantale 56 percé d'un trou central. Encore vers l'aval, une fixation 59 de l'électrode 55 mise à la terre supporte une lentille schématisée en 90, et recevant une alimentation en haute tension positive 95. Enfin, du côté bas, l'électrode 55 est reliée à une enceinte schématisée en 89, isolant la source d'ions de l'ambiance, et permettant d'y faire le vide partiel souhaitable pour son fonctionnement.Above the ion source is placed the electrode 55, which here takes on an annular shape pierced with a central hole 58 for the passage of the ions produced. Slightly downstream of this hole 58, the electrode 55 supports a tantalum heat shield 56 pierced with a central hole. Still downstream, a fixing 59 of the grounded electrode 55 supports a lens shown diagrammatically at 90, and receiving a positive high voltage supply 95. Finally, on the bottom side, the electrode 55 is connected to an enclosure shown schematically in 89, isolating the ion source from the atmosphere, and making it possible to create a partial vacuum desirable for its operation.

La lentille 80 est choisie suivant l'utilisation pour laquelle est prévue la source d'ions. Pour une sonde ionique, la lentille 90 sert à créer une image réelle de la source ponctuelle virtuelle que constitue la source d'ions de l'invention.The lens 80 is chosen according to the use for which the ion source is intended. For an ion probe, the lens 90 is used to create a real image of the virtual point source that constitutes the ion source of the invention.

Les expérimentations qui ont été menées ont pu montrer que la source virtuelle obtenue à l'aide de cette source d'ions possède un diamètre de l'ordre de 50 µm, pour les dimensions illustrées sur les dessins.The experiments which have been carried out have been able to show that the virtual source obtained using this ion source has a diameter of the order of 50 μm, for the dimensions illustrated in the drawings.

Ce montage possède par rapport à l'art antérieur les avantages qui ont été exposés plus haut.This arrangement has over the prior art the advantages which have been explained above.

Le coeur de la sonde est constitué par le capuchon 51, la chicane, qui doit être la plus mince possible (distance entre les surfaces 20 et 25), et l'électrode d'extraction 55 dont le rôle est d'établir un champ électrique le plus qrand possible au niveau de la surface 20 de l'ioniseur pour assurer l'extraction des ions. En effet, un champ extracteur très fort permet d'obtenir une qrande brillance sans qu'il soit nécessaire d'augmenter le diamètre de l'orifice 50.The core of the probe consists of the cap 51, the baffle, which must be as thin as possible (distance between the surfaces 20 and 25), and the extraction electrode 55 whose role is to establish an electric field as large as possible at the surface 20 of the ionizer to ensure the extraction of ions. Indeed, a very strong extractor field makes it possible to obtain a high gloss without the need to increase the diameter of the orifice 50.

En fonctionnement avec un champ extracteur élevé, il a été observé que des ions du faisceau émis peuvent venir frapper la paroi de l'électrode de focalisation 55 autour de son trou 58. L'électrode 55 est faite d'un matériau, comme le Tantale, émettant peu d'ions négatifs sous l'effet du bombardement des ions positifs du faisceau. Mais ce bombardement ionique positif va créer des électrons qui reviennent bombarder le capuchon 51 à + 10 kV.In operation with a high extractor field, it has been observed that ions of the emitted beam can strike the wall of the focusing electrode 55 around its hole 58. The electrode 55 is made of a material, such as Tantalum , emitting few negative ions due to the bombardment of positive ions in the beam. But this positive ion bombardment will create electrons which return to bomb the cap 51 at + 10 kV.

Ce phénomène parasite crée un chauffage supplémentaire du capuchon (et de l'ensemble de l'ioniseur). Ceci accroît le débit de l'alimentation, et peut rendre impossible le contrôle de la température de l'ioniseur.This parasitic phenomenon creates heating additional cap (and the entire ionizer). This increases the feed rate, and may make it impossible to control the temperature of the ionizer.

Une variante préférentielle illustrée aux figures 4 et 4A tire avantage du phénomène parasite qui vient d'être décrit.A preferred variant illustrated in FIGS. 4 and 4A takes advantage of the parasitic phenomenon which has just been described.

Sous l'électrode 55, et autour de son orifice 58, on place un insert isolant 57A supportant une électrode annulaire 57 dont le bord interne, libre, est coaxial à l'orifice 58;Under the electrode 55, and around its orifice 58, an insulating insert 57A is placed supporting a ring electrode 57 whose internal, free edge is coaxial with the orifice 58;

En appliquant à cette électrode supplémentaire 57 une tension de polarisation P = - 320 V environ, on bloque les électrons secondaires (et les quelques ions secondaires négatifs) dus au bombardement de l'électrode de focalisation 55 par les ions primaires positifs.By applying to this additional electrode 57 a bias voltage P = - 320 V approximately, the secondary electrons (and the few negative secondary ions) due to the bombardment of the focusing electrode 55 by the positive primary ions are blocked.

Mieux, en appliquant au contraire à l'électrode supplémentaire 57 une tension p = + 320 V environ, on focalise lesdits électrons secondaires (voire les ions secondaires sur la surface 20 de l'ioniseur, comme schématisé sur la figure 4A.Better, by applying on the contrary to the additional electrode 57 a voltage p = + approximately 320 V, said secondary electrons (or even the secondary ions) are focused on the surface 20 of the ionizer, as shown diagrammatically in FIG. 4A.

Le fonctionnement de la source d'ions est alors lancé par chauffage du capuchon 51 à l'aide du filament F, comme précédemment. Ensuite, on règle la polarisation de l'électrode supplémentaire 57 pour focaliser les électrons secondaires sur la surface ionisante 20. On peut alors arrêter le chauffage par le filament F, ou le diminuer pour un chauffage d'appoint assurant la compensation des pertes thermiques des parois externes de l'ensemble ioniseur (organes 1 à 5).The operation of the ion source is then started by heating the cap 51 using the filament F, as before. Then, the polarization of the additional electrode 57 is adjusted in order to focus the secondary electrons on the ionizing surface 20. It is then possible to stop the heating by the filament F, or decrease it for an auxiliary heating ensuring the compensation of the heat losses of the external walls of the ionizer assembly (organs 1 to 5).

On décrira maintenant différentes variantes de l'invention.We will now describe different variants of the invention.

Dans ce qui précède, le rôle de surface active de l'ioniseur est joué essentiellement par la surface 20. Mais ce rôle peut être joué aussi, dans une certaine mesure, par n'importe quelle surface du même métal portée à une température suffisante, ce qui est le cas pour la face interne 25 du capuchon, et pour les surfaces laterales 21 à 24, comme précédemment indiqué. Les ions ainsi produits latéralement peuvent aller sur la surface active 20, repartir dans le même état (d'ions) et subir ensuite l'accélération qui les fera sortir par l'orifice de sortie 50, puis par le trou 58 (figure 3).In the foregoing, the role of active surface of the ionizer is played essentially by surface 20. But this role can also be played, to a certain extent, by any surface of the same metal brought to a sufficient temperature, which is the case for the internal face 25 of the cap, and for the lateral surfaces 21 to 24, as previously indicated. The ions thus produced laterally can go to the active surface 20, leave again in the same state (of ions) and then undergo the acceleration which will make them exit by the exit orifice 50, then by the hole 58 (FIG. 3) .

Toutefois, les ions qui sont émis par la surface 25, dans sa couronne circulaire proche du trou 50, voient un champ électrique qui peut leur imprimer une trajectoire incurvée, qui les mène sans autre impact jusqu'à sortir par les trous 50 et 58.However, the ions which are emitted by the surface 25, in its circular ring close to the hole 50, see an electric field which can give them a curved trajectory, which leads them without other impact until exiting through the holes 50 and 58.

Ceci n'altère pas la petite taille de la source virtuelle obtenue selon l'invention. Cet effet paraît plutôt de nature à renforcer l'intensité délivrée par cette source.This does not alter the small size of the virtual source obtained according to the invention. This effect seems rather likely to reinforce the intensity delivered by this source.

Il en résulte cependant que le faisceau d'ions émis ne possède pas une distribution sensiblement gaussienne centrée sur sa direction principale D, mais au contraire une distribution assez large, plutôt renforcée, sur une couronne périphérique de ce faisceau;However, the result is that the emitted ion beam does not have a substantially Gaussian distribution centered on its main direction D, but on the contrary a fairly wide, rather reinforced, distribution on a peripheral ring of this beam;

Dans l'application à une sonde ionique, on est amené à diminuer la taille de la source virtuelle par un système optique réducteur composé d'une ou plusieurs lentilles électrostatiques (90). En raison de l'invariant optique, toute réduction de taille du faisceau par ce moyen produit une augmentation de l'angle d'ouverture et par suite, une augmentation des aberrations d'ouverture, ce qui va à l'encontre du but, à savoir produire une sonde de petite taille. Cet effet oblige à réduire l'angle d'ouverture, par interposition de diaphragmes convenablement disposés. Dans ces conditions, comme les ions issus de la couronne circulaire précitée n'alimentent pas les angles d'ouverture les plus petits, ils ne sont pas utiles à la création d'une sonde ionique.In the application to an ion probe, it is necessary to reduce the size of the virtual source by a reducing optical system composed of one or more electrostatic lenses (90). Because of the optical invariant, any reduction in beam size by this means produces an increase in the aperture angle and therefore an increase in aperture aberrations, which defeats the purpose, at know how to produce a small probe. This effect makes it necessary to reduce the opening angle, by interposing suitably arranged diaphragms. Under these conditions, as the ions coming from the abovementioned circular crown do not feed the smallest opening angles, they are not useful for the creation of an ion probe.

Pour cette application, l'invention prévoit (figure 2C) que l'on place sur la face interne 25 du capuchon un disque mince d'hexaborure de lanthane, noté 64A, et percé d'un trou central sensiblement de même taille que l'orifice 50. Le disque 64A peut être remplacé par un dépôt d'hexaborure de lanthane réalisé par évaporation sous vide. L'épaisseur étant moindre, le champ électrique d'extraction est augmenté.For this application, the invention provides (FIG. 2C) that a thin disc of lanthanum hexaboride, denoted 64A, is placed on the internal face 25 of the cap and pierced with a central hole substantially the same size as the orifice 50. The disk 64A can be replaced by a deposit of lanthanum hexaboride produced by vacuum evaporation. The thickness being less, the electric field of extraction is increased.

Contrairement aux métaux, l'hexaborure de lanthane possède un travail de sortie plus faible que l'énergie d'ionisation du césium (par exemple). Il en résulte que les atomes de césium ayant frappé le disque d'hexaborure de lanthane repartent sous forme d'atomes neutres, et viennent alors frapper la surface actie 20A, qui est la seule surface ionisante.Unlike metals, lanthanum hexaboride has a lower output work than the ionization energy of cesium (for example). As a result, the cesium atoms which have struck the lanthanum hexaboride disc leave in the form of neutral atoms, and then strike the actie surface 20A, which is the only ionizing surface.

On pouvait craindre, en agissant ainsi, de perdre dans le faisceau d'ions produits la contribution qui intervenait précédemment du fait de la couronne de la pièce 25 et qui entoure l'orifice 50. De façon assez inattendue, il en a été tout autrement: les conditions d'alimentation de la surface active 20A en atomes d'alcalin se sont modifiées dans un sens favorable à l'amélioration de la brillance de la source. Ceci n'est pas entièrement expliqué, mais peut tenir à d'autres effets, dont l'émission électronique de l'hexaborure de lanthane, et la différence de potentiel de contact entre ce corps et celui de la plaque, qui crée un champ électrique entre la face interne de la plaque 64A et la surface active 20A. Il se peut qu'interviennent également des effets de charges d'espace, qui seraient différents avec la disposition de la figure 2A et celle de la figure 2C.It was feared, by doing so, to lose in the ion beam produced the contribution which previously occurred due to the crown of the part 25 and which surrounds the orifice 50. Quite unexpectedly, it was quite different : the conditions for supplying the active surface 20A with alkali atoms have been modified in a direction favorable to improving the brightness of the source. This is not fully explained, but may be due to other effects, including the electronic emission of lanthanum hexaboride, and the difference in contact potential between this body and that of the plate, which creates an electric field. between the internal face of the plate 64A and the active surface 20A. Space charge effects may also occur, which would be different with the arrangement in Figure 2A and that in Figure 2C.

D'un autre côté, il s'est avéré que l'on pouvait augmenter encore le caractère ponctuel de la source obtenue, en bombant autant que possible la surface active 20A de la plaque 62. En d'autres termes, on donne à cette surface 20A (ou à la surface 20 de la figure 2A) une forte convexité tournée vers l'orifice 50.On the other hand, it has been found that the point nature of the source obtained can be further increased, by bending the active surface 20A of the plate 62 as much as possible. In other words, this is given surface 20A (or on the surface 20 of FIG. 2A) a strong convexity facing the orifice 50.

Le faisceau d'ions ainsi obtenu convient alors particulièrement bien pour la réalisation d'une sonde ionique.The ion beam thus obtained is then particularly suitable for producing an ion probe.

En d'autres applications,on peut rechercher à produire un faisceau conique creux au centre. Il conviendrait alors de remplacer la plaque 62, du moins au niveau de la surface 20, par une plaque en hexaborure de lanthane, et de faire jouer le rôle de support d'ionisation exclusivement à la couronne circulaire de la surface 25 qui entoure l'orifice 50.In other applications, it may be sought to produce a hollow conical beam in the center. It would then be advisable to replace the plate 62, at least at the level of the surface 20, by a lanthanum hexaboride plate, and to play the role of ionization support exclusively at the circular crown of the surface 25 which surrounds the orifice 50.

Dans de qui précède, on a examiné la production d'ions positifs. La source de l'invention permet également la production d'ions négatifs, en faisant passer bien entendu à - 10 kilovolts la tension entre l'ioniseur et l'électrode 55. Dans ce cas, l'électrode supplémentaire 57, polarisée à + 320 V, sert au blocage des ions positifs.In the foregoing, the production of positive ions was examined. The source of the invention also allows the production of negative ions, by of course passing the voltage between the ionizer and the electrode 55 to -10 kilovolts. In this case, the additional electrode 57, polarized at + 320 V, is used to block positive ions.

On remarque immédiatement que la dernière variante de la figure 2A qui vient d'être décrite possède ume surface 25 métallique et une surface 20 en hexaborure de lanthane. Pour des ions négatifs, relatifs à des éléments dont l'affinité électronique est élevée, on produira alors un faisceau d'ions partant de la surface 20. Ce faisceau d'ions est du type très ponctuel convenant pour les sondes ioniques. Par exemple, on place dans le réservoir des cristaux d'iode, qui produisent une vapeur d'iode par chauffage léger. Les atomes d'iode ne s'ionisent pas sur le métal, alors qu'ils le feront sur l'hexaborure de lanthane.It is immediately noted that the last variant of FIG. 2A which has just been described has a metal surface 25 and a surface 20 in lanthanum hexaboride. For negative ions, relating to elements with a high electronic affinity, an ion beam starting from the surface 20 will then be produced. This ion beam is of the very point type suitable for ion probes. For example, iodine crystals are placed in the tank, which produce iodine vapor by gentle heating. Iodine atoms do not ionize on metal, whereas they will ionize on lanthanum hexaboride.

Si, inversement, on souhaite un faisceau d'ions iode conique et creux au centre, on utilisera alors un montage tel que celui de la figure 2C, où la surfacé 20A n'a cependant plus besoin d'être bombée.If, conversely, a beam of conical and hollow iodine ions is desired in the center, then an arrangement such as that of FIG. 2C will be used, where the surface 20A does not need to be curved, however.

Enfin, s'il est intéressant de fournir un faisceau très intense, possédant des ions aussi bien au centre qu'en périphérie, on peut encore utiliser le montage de la figure 2C, mais en utilisant de l'hexaborure de lanthane non seulement pour la plaque 64A, mais aussi pour la surface active 20A, qui, dans ce dernier cas, peut à nouveau être bombée.Finally, if it is interesting to provide a very intense beam, having ions both in the center and in the periphery, we can still use the assembly of Figure 2C, but using lanthanum hexaboride not only for the plate 64A, but also for the active surface 20A, which, in the latter case, can again be curved.

Plus généralement, des ions négatifs pourront être créés à partir d'halogènes, à savoir non seulement d'iode, mais aussi de chlore par exemple. Il est également envisageable de produire des ions négatifs à partir d'atomes alcalins, quoique leur intérêt soit alors plus limité.More generally, negative ions can be created from halogens, namely not only iodine, but also chlorine for example. It is also conceivable to produce negative ions from alkaline atoms, although their interest is then more limited.

En règle générale, la probabilité d'ionisation, pour des ions positifs, est grande lorsque le matériau de la surface active possède, pour ces ions, un travail de sortie supérieur à leur potentiel d'ionisation.As a general rule, the probability of ionization for positive ions is high when the material of the active surface has, for these ions, an output work greater than their ionization potential.

Pour des ions négatifs, il est souhaitable que le matériau de la surface active possède, pour ces ions, un travail de sortie inférieur à leur affinité électronique.For negative ions, it is desirable that the material of the active surface has, for these ions, an output work lower than their electronic affinity.

Dans ce qui précède, on a attaché une grande importance à la probabilité d'ionisation ou à l'affinité électronique.In the foregoing, great importance has been attached to the probability of ionization or to electronic affinity.

Cela est souhaitable lorsqu'on désire construire une source d'ions de forte brillance, qui forme une sorte de canon à ions.This is desirable when it is desired to build an ion source of high brightness, which forms a kind of ion gun.

Une application assez différente consiste à utiliser la source d'ions placée à l'entrée d'un spectromètre de masse pour analyser un matériau inconnu. Ce matériau est placé dans le réservoir 1, chauffé, et dégage des atomes (neutres ou déjà ionisés) qui représentent la nature dudit matériau.Ces ions peuvent très bien être transformés en faisceau en utilisant une source selon la présente invention. Dans une telle application, la brillance de la source importe beaucoup moins. Par contre, les autres avantages demeurent, à savoir:

  • - le fait qu'une pression de vapeur importante n'est pas requise au niveau de la source de particules neutres; - la maîtrise de la géométrie du faisceau et le fait que la surface émissive d'ions est petite;
  • - le fait que toute atome neutre est obligé de rencontrer l'ioniseur avant de sortir de la source;
  • - la possibilité d'utiliser des tensions d'accélération importantes.
A quite different application is to use the ion source placed at the entrance of a mass spectrometer to analyze an unknown material. This material is placed in the tank 1, heated, and gives off atoms (neutral or already ionized) which represent the nature of said material. These ions can very well be transformed into a beam using a source according to the present invention. In such an application, the brightness of the source is much less important. On the other hand, the other advantages remain, namely:
  • - the fact that a significant vapor pressure is not required at the source of neutral particles; - control of the beam geometry and the fact that the ion emitting surface is small;
  • - the fact that any neutral atom is obliged to meet the ionizer before leaving the source;
  • - the possibility of using high acceleration voltages.

On notera que la géométrie de l'orifice 50 n'est pas forcément circulaire. Cette géométrie peut dépendre de la forme du faisceau d'ions qui est désirée pour travailler en aval.It will be noted that the geometry of the orifice 50 is not necessarily circular. This geometry may depend on the shape of the ion beam which is desired for working downstream.

On notera, en outre, que la source d'ions vient d'être décrite dans son utilisation en position verticale. Pour une utilisation inclinée ou horizontale, la disposition relative des éléments est bien entendu conservée mais la source de neutres 1 sera aménagée en conséquence pour contenir le composé solide 10.It will also be noted that the ion source has just been described in its use in a vertical position. For inclined or horizontal use, the relative arrangement of the elements is of course retained, but the source of neutrals 1 will be arranged accordingly to contain the solid compound 10.

Claims (21)

1. Ion source functioning by surface ionization, of the type comprising, under vacuum,
- a source (1) of neutral particles, of the same nature as the ions to be produced,
- means (3, 5) defining with this source (1) a closed conduit (30) except for an end orifice (50) situated away from the said source (1),
- an ionization support (2) which has, facing the orifice (50), a suitable active surface (20) for the adsorption of the neutral particles, followed by their desorption in the form of ions, this ionization support being arranged in the closed conduit and forming a baffle (6) which acts as an obstacle to the passage of the neutral particles in the emitted ion beam, and
- means (5) for focusing the ions thus produced through the orifice (50) into a beam emitted in a chosen direction (D) in space,
characterized in that the ionization support (2) is defined by thin conductive components (61 to 64), all thin stacked so that they internally form a cylindrical passage (21 to 24) coaxial with the exit orifice, and with a cross-section smaller than that of the said closed conduit (3), and in that the baffle (6) is defined by the fact that the said component (62) without a central hole is a plate pierced only by peripheral holes (65, 68) inside the passage, that it passes through, while its central part defines the said active surface (20) facing the exit orifice (50), and this produces a virtually perfect baffle preventing the direct passage of the neutral particles into the emitted beam, without their having struck the active surface (20, 25) of the ionization support.
2. Ion source according to Claim 1, characterized in that the ionization support (2) is housed inside a conductive hood (51), mounted on the end of the said conduit (30), which is completely closed by the hood (51), except at the latter's exit orifice (50).
3. Ion source according to Claim 2, characterized in that the means (5) of focusing comprise an outer focusing electrode (55) pierced (58) and raised in order to establish, between the active surface (20) and the exit orifice (50), a suitable electrical field for accelerating the ions in order to form the emission beam.
4. Ion source according to Claim 3, characterized in that the potential difference between the active surface (20) and the outer electrode (55) is of the order of at least 10 kilovolts, the size of the exit orifice (50) being of a few tenths of millimetres, and the latter being widened outwards.
5. Ion source according to one of Claims 1 to 4, characterized in that it comprises suitable means (F, 86) for heating the ionization support (2), preferably to a temperature of between 1,000 and 1,500° C
6. Ion source according to one of Claims 1 to 5, characterized in that the conduit (30) connecting the source (1) of neutral particles to the ionization support (2) is of dimensions which are chosen in order to preserve the baffle effect.
7. Ion source according to one of Claims 1 to 6, characterized in that the source of neutral particles (1) comprises a suitable compound for yielding the said particles by pyrolysis.
8. Ion source according to Claim 7, characterized in that it comprises means for heating the source of neutral particles separately.
9. Ion source according to one of Claims 1 to 8, characterized in that the active surface (20A) of the ionization support is very bulging opposite the exit orifice.
10. Ion source according to one of the preceding claims, characterized in that the particles are atoms of an alkali metal.
11. lon source according to one of Claims 1 to 9, characterized in that the particles are atoms of a halogen.
12. Ion source according to one of Claims 1 to 10, characterized in that, when the ions are positive, the material of the active surface has, for these ions, a work of emission which is higher than their ionization potential.
13. lon source according to Claim 12, characterized in that the ions are of caesium, rubidium or potassium, and in that the active surface is metallic.
14. lon source according to Claim 13, characterized in that the inner face of the hood (51) comprises a thin disc of lanthanum hexaboride (64A) pierced with a central hole corresponding to the exit orifice (50).
15. Ion source according to one of Claims 1 to 11, characterized in that, when the ions are negative, the material of the active surface has, for these ions, a work of emission which is lower than their electron affinity.
16. lon source according to Claim 15, characterized in that the ions are of iodine or of chlorine, and in that the active surface is made of a material with a low work of emission, such as lanthanum hexaboride.
17. Ion source according to one of Claims 3,4 or 5 to 16, taken subsidiarily to Claim 3, characterized in that the focusing electrode (55) is equipped upstream with an additional electrode (57) making it possible to control the return, towards the ionization support, of secondary particles generated as a result of the electron bombardment of the focusing electrode (55).
18. Ion source according to Claim 17, characterized in that, when the primary ions are positive, the additional electrode (57) is polarized in order to block the beam of secondary electrons.
19. lon source according to Claim 17, characterized in that, when the primary ions are positive, the additional electrode (57) is polarized in order to focus the beam of secondary electrons onto the active surface (30) of the ionization support, through the exit orifice (50) of the hood (51), and this at least partially ensures the heating of the ion source.
20. Ion source according to either of Claims 18 and 19, characterized in that the focusing electrode (55) is made of tantalum.
21. lon source according to one of the preceding claims, characterized in that, downstream of the exit orifice (50) and of the focusing electrode (55), it comprises a reducing optical system permitting its use as a very fine and very bright ion probe.
EP85400969A 1984-05-16 1985-05-15 Surface ionisation-type ion source, particularly for the realisation of an ionic probe Expired EP0165140B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8407606A FR2564636B1 (en) 1984-05-16 1984-05-16 SOURCE OF IONS OPERATING BY SURFACE IONIZATION, IN PARTICULAR FOR THE REALIZATION OF AN IONIC PROBE
FR8407606 1984-05-16

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EP0165140A1 EP0165140A1 (en) 1985-12-18
EP0165140B1 true EP0165140B1 (en) 1988-05-18

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EP (1) EP0165140B1 (en)
JP (1) JPS6151729A (en)
DE (1) DE3562842D1 (en)
FR (1) FR2564636B1 (en)
SU (1) SU1473724A3 (en)

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US11031205B1 (en) 2020-02-04 2021-06-08 Georg-August-Universität Göttingen Stiftung Öffentlichen Rechts, Universitätsmedizin Device for generating negative ions by impinging positive ions on a target

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IL81375A (en) * 1987-01-23 1990-11-05 Univ Ramot Method and apparatus for producing ions by surface ionization of energy-rich molecules and atoms
US4954750A (en) * 1988-07-07 1990-09-04 Albert Barsimanto Flexible ion emitter
JPH042031A (en) * 1990-04-18 1992-01-07 Matsushita Electric Ind Co Ltd Ion source device
GB2460664A (en) * 2008-06-04 2009-12-09 Hiden Analytical Ltd A surface ionization ion source

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US2486452A (en) * 1945-04-30 1949-11-01 Cons Eng Corp Mass spectrometry
FR65999E (en) * 1954-05-25 1956-03-27
US3283193A (en) * 1962-05-14 1966-11-01 Ellison Company Ion source having electrodes of catalytic material
US3336475A (en) * 1964-02-05 1967-08-15 Electro Optical Systems Inc Device for forming negative ions from iodine gas and a lanthanum boride contact ionizer surface
US3864575A (en) * 1970-07-25 1975-02-04 Nujeeb Hashmi Contact ionization ion source
DE2222396B2 (en) * 1972-05-06 1975-04-30 Bodenseewerk Perkin-Elmer & Co Gmbh, 7770 Ueberlingen Selective ionization detector
JPS57205953A (en) * 1981-06-12 1982-12-17 Jeol Ltd Ion source

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11031205B1 (en) 2020-02-04 2021-06-08 Georg-August-Universität Göttingen Stiftung Öffentlichen Rechts, Universitätsmedizin Device for generating negative ions by impinging positive ions on a target

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FR2564636A1 (en) 1985-11-22
US4801849A (en) 1989-01-31
FR2564636B1 (en) 1990-07-06
JPH0451929B2 (en) 1992-08-20
DE3562842D1 (en) 1988-06-23
JPS6151729A (en) 1986-03-14
SU1473724A3 (en) 1989-04-15
EP0165140A1 (en) 1985-12-18

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