WO1994003919A1

WO1994003919A1 - Process and device for generating beams of any highly charged ions having low kinetic energy

Info

Publication number: WO1994003919A1
Application number: PCT/EP1993/002047
Authority: WO
Inventors: Jürgen ANDRÄ
Original assignee: Andrae Juergen
Priority date: 1992-08-08
Filing date: 1993-07-30
Publication date: 1994-02-17
Also published as: AU4705593A

Abstract

A plasma chamber (5) is disclosed in which the vacuum required for generating the plasma is generated and in which the microwaves are input, with a plasma electrode (10) and an extraction electrode (13) through which the generated ions are extracted from the plasma, a so-called drawing field being formed between the plasma electrode and the extraction electrode by a potential difference (about 20 kV). The plasma chamber (5) is equipped with one or several material evaporating ovens (8) which allow plasmas and thus ions of any desired elements to be generated. An electrically and magnetically directed electron beam (12) generated in the extraction electrode (13) is superimposed on the ion beam (11) coming from the plasma chamber (5) and running through the plasma and extraction electrodes (10 and 13), so that an electronic extraction channel with space charge compensation for the ions is formed.

Description

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Method for generating rays of any high-energy ions with low kinetic energy and device for carrying out the method

The invention relates to a method for generating rays of any highly charged ions of low kinetic energy (approximately 1 to 200 eV) with good brilliance according to the preamble of claim 1.

It is known to extract highly charged ion beams from EZR ion sources with high yield. The design features of known EZR ion sources are known from patent documents (EP 138 642, 130 607, 142 414, 145 584, 238 397, 252 845 and French laid-open documents 24 75 798, 25 12 623, 25 92 518) and other scientific and technical publications . According to the previous publications, a plasma is enclosed by two or more circular, not necessarily identical magnetic coils that are at a certain axial distance from one another. A maximum of the magnetic field strength arises at the location of the coils on the axis of symmetry of the enclosed plasma and a minimum between the coils. This magnetic field structure can be realized with conventional or with superconducting coils with the same or opposite current direction. In more recent designs, this axial magnetic field structure is also used with permanent magnets without Ver using coils. The radial plasma confinement is effected by magnetic multipole sensors, usually hexapoles, which are usually constructed with permanent magnets. However, superconducting coils or iron-reinforced copper coils can also be used.

A cylindrical plasma chamber made of metal is used in this magnetic field structure on the axis of symmetry, which essentially serves as a vacuum chamber. A low pressure of 10 ^-1 to 10 ^-3 Pa of the gas or gas mixture to be ionized is maintained in the plasma chamber. The gas inlet takes place directly into the plasma chamber or into the pump lines between the vacuum pumps and the plasma chamber, with very often not only the gas to be ionized but also a so-called support gas being let in. The microwave energy is coupled into the plasma chamber radially or axially with high-frequency waveguides or with coaxial lines, possibly in combination with antennas, a microwave-permeable but vacuum-tight window ensuring the vacuum closure of the plasma chamber. The plasma electrode is a pierced electrode through which the ions are extracted axially using a drawing field. This plasma electrode is arranged in the area of one of the two axial magnetic field maxima, hereinafter referred to as the front one. The drawing field is built up by the voltage difference between the plasma electrode and another, pierced electrode, the so-called extraction electrode. The plasma electrode and the entire plasma are at a more positive potential than the extraction electrode.

The geometrical shape and the axial distance of the plasma and extraction electrodes as well as their position relative to the magnetic field maximum and plasma partly determine the brilliance of the extracted ion beam. It is known to optimize the brilliance by the electrode gap and the axial magnetic field maximum can be varied during operation until the best brilliance of a desired ion type is achieved.

The brilliance of an ion beam is defined as the ion current of a given emittance, i.e. H. per beam cross-sectional area and solid angle, which are filled by the ion beam. The surface normal and the axis of symmetry of the solid angle lie on the beam axis. The smaller the emittance and the greater the brilliance, the better the ion source with its extraction, because the brilliance cannot be improved by ion-optical manipulation (Liouville theorem). The brilliance is the measure for the achievable ion current per unit area and solid angle on a target surface.

In the continuous operation of such EZR ion sources, high absolute ion currents of medium charge q _m = ½ · Z can be achieved. (Z = atomic number of the corresponding gaseous element).

Elements that are solid at room temperature are either introduced into the plasma in the form of gaseous chemical compounds or evaporated into the plasma or evaporated from the plasma itself after the element in question has been introduced into a plasma chamber in solid form. In principle, ions of all elements can be generated with such EZR ion sources.

A disadvantage of EZR ion sources is their relatively poor emittance relative to other ion sources, especially to electron beam ion sources. Despite absolutely high ion currents, optimal brilliance is not achieved. In applications where low-energy, highly charged ions are required, the non-optimal brilliance is a very disturbing, limiting

The reasons for the relatively poor emittance of EZR ion sources are to be found in the very large plasma emission area and in the large extraction current of several mA.

The plasma emission area is defined through the opening in the plasma electrode. This must necessarily be large in order to obtain a good acceleration field penetration up to the charged ions in the front EZR zone on the axis of symmetry. This leads to strong space charge expansions, which irreversibly deteriorate the emittance even over short stretches of an extraction stream. In addition, the average charge state of the extracted ions is reduced, since the ions have to pass through an area of neutral gases with significant density from the front of the EZR ion source to the extraction electrode, where they lose charge due to so-called resonant electron capture.

As an alternative to EZR ion sources, electron beam ion sources are known for the production of ion currents from highly charged ions. An intense electron beam of given energy generates a mixture of charge states of the gas element up to high charge states in a given density in the geometric range of the highest electron beam density. These uploaded ions are extracted either radially or axially from the area of high electron beam density with an electric pull field. This is generated between a pair of electrodes. Radial extraction does not allow an increase in the electron beam density due to a magnetic field running axially to the electron beam and requires the charged ions to pass through zones of relatively high gas density. at Axial extraction eliminates these disadvantages, so that only ion sources with axial extraction are discussed below, for which the EBIS source ("Electron Beam Ions Source") [MP Stöckli, Zeitschrift für Physik D, Zeitschrift für Physik D, volume 21, Supplement, pages Slll to S115, 1991] and the EBIT source

("Electron Beam Ion Trap") [D. Schneider, M.W. Clark, B.M. Penetrante, J. McDonald, D. DeWitt, and J.N. Bardsley, Physical Review A, Volume 44, pages 3119 to 3124, 1991] are the outstanding examples. EBIS and EBIT sources result in an intense, axial electron beam in an axial magnetic field. The magnetic field ensures the radial confinement of the ions, while the axial ion confinement can be ensured by pierced, negative electrode disks at the entrance and exit of the electron beam.

In the EBIS source, the ions are stored in an axial, mostly superconducting magnetic field structure over a relatively long distance of a few decimeters and exposed to the axial electron beam over their entire length in order to generate higher charge states through successive ionization, whereby the electron beam compressed in the magnetic field together acts as an ion trap with the magnetic field. After a selectable storage time of the ions, they are extracted axially from the source in the form of an ion beam pulse by changing the potentials of the pierced electrodes. On average, the EBIS source can be used to generate higher charge states with smaller absolute ion currents, but with much better emittance than with EZR sources, so that the brilliance of the EBIS source is greater, especially for highly charged ions than for EZR sources. With medium charge states q _m = ½. Z. the absolute ion currents from the EBIS source are not sufficient to compete with the brilliance of the EZR source. EBIS sources also require a very high technical effort, which practically excludes their industrial use. The introduction of elements into the EBIS source, which are present at room temperature, is also very difficult, but is possible with high financial and technical effort in the form of ion injection.

In the EBIT source, the highest possible axial magnetic field with superconducting coils is generated over a distance of a few centimeters, in which an intense axial electron beam is maximally compressed on this route and very high electron beam densities are achieved. These electron densities are so great that the electron beam, supported by the magnetic field, serves as a radial ion trap on this route, which is axially closed electrostatically by a negative pair of electrodes. In this ion trap the absolutely highest charge states with q = 82 are generated, which are less likely to be axially extracted after a selectable storage time by electrically opening the trap. The ion currents that can be achieved in this way are very high and absolutely very small. Since the compressed electron beam has an extremely small diameter of the order of a few tens of μm, the ions can be extracted with very good emittance, as with the EBIS source, so that the brilliance of the EBIT source can be expected to be attractive values for very high charge states. With medium charge states q _m = ½ · Z, the absolute ion currents of the EBIT source are not sufficient to compete with the brilliance of the EZR source to be able to. EBIT sources also require a very high technical outlay, which practically excludes the industrial use of previously known embodiments. The introduction of elements into the EBIT source that are permanently available at room temperature also creates great difficulties.

In summary, it can be stated that EZR ion sources with high absolute ion currents of medium charge state, but only moderate emittance and electron beam ion sources with very good emittance, but only small absolute ion currents of medium and high charge state exist and that for both types of ion sources the introduction is more solid Elements is not solved satisfactorily. This situation limits the use of highly charged ions, especially in applications where low-energy ions are required, because the deceleration of ion beams basically lowers their brilliance by a factor of E ₁ / E ₂ , E _{1 being} the

Extraction energy per charge and E ₂ mean the decelerated energy of the ions per charge, so that the extraction brilliance must be as high as possible in order to achieve satisfactory brilliance of the decelerated ion beams.

The fundamental problem of ion beam rotation about the ion beam axis, which arises from the extraction acceleration from areas with radial magnetic field components of all magnetic field-supported ion sources and correspondingly worsens the emittance, is also disadvantageous for all applications where low-energy ion beams that are as parallel as possible are required.

Accordingly, there are two tasks, namely to combine the basic principles of EZR and electron beam ion sources in order to take advantage of the respective advantages and to reduce the respective disadvantages and to eliminate the ion beam rotation by suitable measures.

The first object is achieved in a method for operating an ion source device of the type mentioned at the outset, which is characterized in that the ion beam coming from the plasma chamber and passing through the extraction electrode opens up behind the extraction electrode front surface (viewed in the direction of the ion beam) and is generated by the existing magnetic field the axis converging electron beam is sent towards the other side, so that a space charge compensating electron extraction channel for the ions is thereby formed. The same basic idea also characterizes an ion source device of the aforementioned type, as follows from the characterizing part of claim 2.

In the method and the ion source device which is suitable for carrying out the method, the basic principles of EZR and electron beam ion sources are quasi combined to form an electron beam EZR hybrid ion source with space charge-compensated extraction for the generation of any uploaded ion beams with good emittance.

The aforementioned electron beam EZR hybrid ion source then results in a space charge-compensated extraction, in that, viewed in the direction of the ion beam behind the extraction electrode front surface and preferably concentrically around the ion beam, an intensive electron emission of approximately 10 to 400 eV energy is generated in such a way that the electron velocity vectors are parallel or superimposed on the magnetic stray field lines of the ion source so that the electrons on spiral tracks can follow these magnetic field lines into the plasma chamber, from the extraction electrode are accelerated to the plasma electrode in the pull field of the ions. As a result, the ion current accelerated from the plasma is compensated for by the electrons in the entire superimposition region. To ensure that this area fills the entire space close to the axis up to the first ion-optical component, the generation of electrons should take place as close as possible to this component. At the same time, in the form of the electron beam compressed in the axial magnetic field of the EZR source, a very small-area extraction channel for highly charged ions from the EZR zone to the extraction electrode is formed by, as with an EBIT source, the uploaded ions in the area of the EZR Zone up to the plasma electrode can be temporarily stored and further ionized.

In this electron beam-EZR hybrid construction, the EZR plasma serves as a supplier of high currents of highly charged ions, which are further ionized by the electron beam and channeled into a good emittance, the electron beam simultaneously increasing the electron density in the EZR plasma, so that the gas density is reduced can be and the average state of charge in the plasma is increased. In principle, all known embodiments of EZR ion sources can be combined with the electron beam. If there is a zero crossing of the field sign of the axial magnetic stray field, the electrons in the immediate vicinity of this zero crossing must be generated with velocity vectors parallel to the magnetic field lines in such a way that they are directed towards the extraction electrode on the side of the zero crossing facing the extraction electrode and on the side facing away from the extraction electrode Side of the zero crossing are directed away from the extraction electrode. Since, in the case of a hybrid ion source, the actual plasma area continues to have an EZR character, in principle everyone can also use her known methods of introducing ionizing elements and support gases in EZR ion sources continue to be used and improved if necessary.

In the ion source device, a metallic extraction electrode with an inner cylinder is preferably used, in which there is an inner channel, on the inner walls of which highly charged ions, which diverge outwards at the periphery of the ion beam, produce secondary electrons with high yield. On the one hand, these compensate for the space charge in the ion beam by means of axial velocity components in the direction of the ion beam; on the other hand, they generate an intense electron beam between the extraction and plasma electrodes by passing through the extraction field, which electron beam is accelerated into the plasma with the potential difference between the plasma and extraction electrodes, so that the ion current accelerated from the plasma between the plasma and the extraction electrode is compensated for space charge. At the same time, the electron beam is compressed in the magnetic field of the EZR ion source, which converges axially in the direction of the plasma electrode, so that there is a very small-area extraction channel for highly charged ions from the EZR zone to the extraction electrode. As with an EBIT source, the uploaded ions in the area from the EZR zone to the plasma electrode are temporarily stored and further ionized.

The extraction electrode preferably has a cylindrical inner channel in which the inner diameter is about 2: 1 to 3: 1 in length. The inner channel can also be designed slightly conical, with it narrowing or widening slightly in the direction of the ion beam. Combinations of straight cylinders, an expanding inner cone and a narrowing inner cone are also possible. These are supposed to are subsumed under the term "substantially cylindrical".

The inner channel of the extraction electrode is advantageously preceded by a front surface surrounding the inlet bore to the inner channel and concave towards the plasma chamber. As a result, the secondary electrons from the extraction hole and the secondary electrons, which are generated by diverging ions on this concave surface itself, are accelerated in a focused manner in the direction of the plasma electrode, a focusing that is intensified by the converging magnetic field lines.

The method can also be carried out in that, viewed in the direction of the ion beam, behind the extraction electrode front surface at the potential of the extraction electrode and concentrically around the ion beam, an intensive low-energy electron emission is directed parallel to the magnetic stray field lines there and concentrically towards the ion beam and axially towards the plasma electrode. On the one hand, this compensates for the space charge in the ion beam behind the extraction electrode front surface and, on the other hand, an intense electron beam is generated between the extraction and the plasma electrode of an EZR ion source. This is accelerated into the plasma with the potential difference between the plasma and extraction electrodes, so that the ion current accelerated from the plasma between the plasma and extraction electrodes is compensated for space charge and at the same time, in the form of the electron beam compressed in the axial magnetic field of the EZR source, a very small-area extraction channel for charged ions from the EZR zone to the extraction electrode.

In the latter method, the electrons are advantageously generated by glow emission with a relatively high anode voltage and are re-opened if necessary slowed down low energy. In this case, electrons are extracted in the desired direction of the magnetic stray lines by glow emission from heating wires arranged conically and about the axis through an anode grid likewise arranged conically. Between the anode grid and a likewise conically arranged braking or post-acceleration grid, they can be braked to a desired energy or post-accelerated. Overheating of the overall arrangement can be prevented by cooling the extraction electrode body.

Alternatively, it is also possible for the electrons to be generated by field emission from micropoint surfaces arranged conically around the axis, and if necessary they can be decelerated or post-accelerated between the anode surface of the micropoints and a conical braking or post-acceleration grid.

The cone geometry can be replaced by a non-rotationally symmetrical emission geometry for the generation of the electrons by glow emission as well as by field emission with microdots, as long as it is ensured that the electrons are guided onto the axis by the magnetic stray field lines or by an additional guide field in the direction of the plasma electrode. this guiding field should influence the ions as little as possible.

The electron beam from the extraction electrode into the plasma can be made so intense with active generation and so much energy can be introduced into the plasma that the coupled microwave power for maintaining the plasma can be reduced to low values, in the limit case even to zero, since the electron beam then the plasma itself is supported with magnetic confinement and, in the limit, even completely gets right.

A significant increase in brilliance and emittance can be achieved if the plasma electrode - even during operation - of the ion source can be moved mechanically, axially relative to the plasma chamber. Furthermore, it is advantageous if both the piasmal electrode, the extraction electrode and possibly also the electron generation can be moved axially independently of one another and with a different stroke relative to the magnetic field structure and to the plasma chamber of the ion source.

A further significant improvement in the principle of the invention can be achieved if special precautions are taken for the introduction of solid elements, in particular by improving the evaporation technique. The material to be evaporated is usually locked in a metal cylinder with a small axial steam outlet opening. This cylinder is thermally insulated, inserted axially from the rear into the EZR source until it touches the rear EZR zone, whereby it is heated.

It is proposed to work with an evaporation cylinder, which is made of heat-resistant material and is arranged at the end of a heat-conducting arm, which is coolable at the other end, and with which the evaporation cylinder can be moved close to an EZR zone located inside the ion source device is.

"Evaporation cylinder" is not to be understood specifically, but generally in the sense of a cylindrical shape. The well thermally conductive arm, the z. B. is formed as a copper tube, is connected to a well-defined heat sink (cooling). The evaporation cylinder can be equipped with thermocouples in the front, in the middle and in the back be equipped, which allow an accurate temperature measurement along its axis. The measured temperature, ie the signal from the heat sensors, is used to regulate the axial feed of the cylinder, so that the desired temperature is set for the optimal evaporation rate of the material to be ionized. The contact between the cylinder and the heat sink should be small for very high temperatures and large for low temperatures.

A drawback of this concept may be the withdrawal of energy from the plasma. In order to avoid this problem, the evaporation cylinder can additionally be provided with a heating coil. By equipping the evaporation cylinder with its own heating coil, its position becomes independent of an EZR zone. The evaporation cylinder can therefore also be placed up to a few decimeters behind the EZR zone on the axis, so that an axial atomic (molecular) steam jet is directed into the plasma chamber. As long as this atomic (molecular) steam jet is directed into the plasma chamber, the evaporation cylinder can also be attached outside the axis of the ion source. This makes it possible to arrange several evaporation cylinders charged with different materials around the ion source axis, which allows the element to be ionized to be successively changed during operation of the ion source.

The evaporation container is preferably provided with a gas flow opening in the direction of the thermally conductive arm. This embodiment preferably applies to all designs of evaporation cylinders.

A two-stage ion source is also advantageously used, in which two plasma confinement zones are provided by a microwave-transparent, differential pump aperture axial hole for the plasma passage are separated from each other. When pumping on the extraction side, a pressure drop is thus formed between the two plasma confinement zones, so that the plasma diffuses from the first zone through the aperture hole into the second zone on the extraction side.

In order to optimize the axial magnetic field structure both for the magnetic confinement of the charged particles in the plasma and for the external generation and guiding of the electrons to be injected, soft iron-supported arrangements with one or more current-carrying coils, which can be supplemented by permanent magnets, or pure soft iron supported Permanent magnet arrangements proposed. These arrangements generate a so-called axial, rotationally symmetrical, magnetic mirror field as for conventional EZR ion sources, which is characterized by a sequence magnetic field maximum, minimum, maximum along the axis, the maxima need not be the same.

When the front maximum (extraction side of the ion source) is generated by a coil, a soft iron support in the form of a coaxial disk lying in front of the coil with an outer diameter that exceeds that of the coil by about 5 cm and with a central bore for the extraction is selected, so that the magnetic field strength outside the iron structure drops as quickly as possible without suffering a zero crossing of the field sign.

The rear field maximum is generated either like the front field by a coil with iron support or by radially arranged permanent magnets supported by soft iron, whereby a zero crossing of the field sign may occur. The soft iron in the latter The arrangement can consist of two concentric rings, the outer diameter of the outer coil exceeding that of the front coil by approximately 5 cm and the inner diameter of the inner one being adapted to the passage for the microwave and gas supply. A multiple of six radially magnetized permanent magnets is arranged between the two rings in such a way that the polygonal outer diameter of the inner ring is fully equipped with permanent magnets. The permanent magnets can have the shape of cuboids or trapezoids, they can also be replaced by a radially magnetized ring. If the other dimensions vary accordingly, one of the two soft iron rings can be omitted.

The field strength of the maxima is thereby increased and the external stray fields of the overall arrangement are reduced in that a soft iron cylinder with the inner diameter of the outer diameter of the front coil and about 5 cm larger outer diameter effects the main magnetic connection from the front soft iron disc to the rear, outer soft iron ring.

A small part of the magnetic flux in this soft iron cylinder is deflected in the radial direction by appropriate shaping shortly behind the coil and in the same way in front of the rear, concentric soft iron rings by a relatively thin, coaxial soft iron disk with a large inner diameter. This creates magnetic shunts through which the field strength of the field minimum between the two maxima can be determined as desired. The soft iron cylinder of the magnetic main circuit therefore has a smaller thickness in the middle than at both ends. The thickness difference for the river deflections in the radial direction changes into the thickness of the two soft iron disks.

The soft iron disks can be on their respective Front and rear sides are covered with current-carrying coils so that the field minimum can be varied electrically during operation of the ion source. The radial field generated by these disks can be strengthened by radially magnetized permanent magnets which are inserted into the slides in a similar manner to that described for the rear, concentric rings.

Since only stray fields are formed in the exterior of this magnetic field concept on the extraction side, the field lines of which converge concentrically to the axis up to the first maximum, the electrons to be injected can be generated in this entire spatial region close to the axis

become. It is only limited by the condition that the stray field should be significantly stronger than other interfering fields, e.g. the earth's magnetic field or the stray field of an ion-optical component.

When the front maximum is generated by permanent magnets, a zero crossing of the field sign cannot be avoided. Such a zero crossing destroys every low-energy electron beam. The electrons to be injected must therefore be generated in the immediate vicinity, but on the side of the zero crossing facing the plasma. As a result, the electrons "see" field lines converging up to the field maximum towards the axis and converge accordingly when they are generated and accelerated tangentially to these field lines. So that enough space for this generation and

If there is acceleration, the field strength increase on the axis on both sides of the zero crossing must not take place too quickly. This slow field increase can be achieved by a soft iron assisted, radially magnetized permanent magnet configuration, as previously described for the rear maximum on the back of the ion source. The main difference consists of the thickness of the two concentric soft iron rings measured in the axial direction and the space between the two rings filled with radially magnetized permanent magnets. The greater this thickness, the slower the increase in field strength, but the higher the costs. It is therefore the most economical compromise between the method and the efficiency of electron generation and the effort for the magnetic field configuration.

For the space charge compensation of the ion beam on the side of the zero crossing facing away from the plasma, the electrons must be generated as just described, but on this side of the zero crossing.

In the space that was previously free between the front and the rear field maximum, a coaxial, as strong as possible multipole field made of permanent magnets was placed in direct contact with the outer wall of the plasma chamber, as was customary so far, in order to ensure the radial magnetic inclusion of the plasma. This permanent magnet multipole field may only be supported by soft iron, i.e. be reinforced that the axial magnetic field described above is not disturbed or only in a well-controlled manner.

The following special features should also be noted:

The aforementioned concept of space charge compensation after extraction and the creation of an extraction channel by an intense electron beam can in principle be applied to all ion sources in which ions have to be extracted from a range of ion production.

A further explanation of the invention takes place on the basis of examples and drawings. The figures of the drawing The details show:

1 shows a schematic structure of a first arrangement of an electron beam EZR hybrid ion source, with details in FIGS. 1a, 1b and 1c;

Figure 2 shows a second embodiment, with details in

Figures 2a and 2b;

Figures 3 and 4 further embodiments, each with details in Figures 3a, 3b and 3c and 4a;

Figure 5 shows a modified embodiment with two or more evaporation cylinders and with details in Figure 5a;

FIG. 6 shows an embodiment of an arrangement for compensating for the intrinsic rotation of the ion beam when braking.

Embodiment 1 (see FIGS. 1, 1a, 1b and 1c)

1, 1a, 1b and 1c schematically show an ion source device for the generation and extraction of ion beams, which corresponds to the CAPRICE type, as is evident from the documents of the European patent 138 642.

A plasma is magnetically enclosed in a plasma zone 1. The magnetic confinement of the plasma in the plasma zone 1 is in this case effected by two coaxial coils 2, which are located in a composite iron yoke 3 (3a to 3f), and a permanent multipole magnet (Quadru-, Hexa- or Octopol) 4. In this example, coaxial discs 3a, 3b with central bores for the Ex are used as soft iron support for the coils traction or selected for the microwave inlet (tube 11) so that the magnetic field strength outside the iron structure drops as quickly as possible without suffering a zero crossing of the field sign. A field strengthening is achieved at the microwave inlet by a soft iron ring 3f.

The field strength of the axial magnetic field 5 (represented schematically by the curve) is thereby increased and the external stray fields of the overall arrangement are reduced in that the outer soft iron cylinder 3c establishes the main magnetic connection between the soft iron disks 3a and 3b. A small part of the magnetic flux in this soft iron cylinder is deflected in the radial direction by appropriate shaping on the inside of the coils by a relatively thin, coaxial soft iron disk 3d and 3e with a large inside diameter. This creates magnetic shunts through which the field strength of the field minimum 6 between the two maxima 7 and 8 can be determined as desired. The outer soft iron cylinder 3c therefore has a smaller thickness in the middle than at its two ends. The difference in thickness for the flow deflections in the radial direction changes into the thickness of the two soft iron disks.

The plasma zone 1 is enclosed by a cylindrical plasma chamber 9 designed as a partial cylinder. High-temperature metals, ceramics or quartz are used for this. A plasma chamber made of electrically conductive material is separated from the soft iron yoke 3 and the multipole magnet 4 by an insulation layer 10.

The microwave power is coupled into the plasma chamber 9 through the coaxial tube 11. A pipe 22, preferably made of copper, is inserted concentrically to the pipe 11 and can be moved axially. A cylindrical ver Steaming container 20 is fitted with the help of a casing 21 at the end of the tube 22, as can also be seen from FIGS. 1b and 1c. The sheath 21 of the cylindrical evaporation container 20 and the support tube 22 assume the role of the inner conductor of a microwave coaxial line, the outer sheath of which forms the tube 11, ie the microwave power is thus coupled into the plasma chamber 9.

At its so-called front end (on the left in FIG. 1), the plasma chamber 9 is closed off by a pierced plasma electrode 12. Furthermore, there is an extraction electrode 13 which has a hollow, cylindrical shape and the end 13 'of which is solid with a cylindrical inner channel 15. The extraction electrode 13 lies opposite the plasma electrode 12 at a negative potential, so that a so-called pulling field is formed between these two electrodes, which extracts an ion beam 16 through the plasma electrode 12 from the plasma 1 created by the coupling of the microwave power, which then forms the inner channel 15 of the Extraction electrode 13 penetrates; the inner channel can therefore also be referred to as an extraction channel. The extraction electrode 13 is axially movable relative to the plasma electrode 12. In order to achieve this mobility, a vacuum-tight bellows 14 is provided for the corresponding

Parts of the ion source device are arranged, as can be seen from FIG. 1.

The shape of the extraction electrode 13 on the side 17 facing the plasma electrode 12 is essential for good emittance and brilliance of the extraction of the ions in the ion beam 16. FIG. 1 a shows the situation in an enlarged view. The axially drilled inner channel 15, through which the ion beam 16 passes, is designed as an elongated cylinder jacket or as a weak, positive or negative cone, the length being centered behave like 2: 1 to 3: 1.

In addition, the front surface 17 of the extraction electrode 13 is made concave in the region up to approximately three times the bore diameter, the radius of curvature of the concavity corresponding approximately to three to five times the radius of the inner channel 15. Parts of the diverging ion beam 16 hit the inner wall of the inner channel 15 and generate there a number of very low-energy secondary electrons, corresponding to approximately q ² , which increases rapidly with the charge of the ions. These secondary electrons have radial but also axial speed components. Together with the passage of the extraction field between the extraction electrode 13 and the plasma electrode 12, between which there is a voltage difference for the ion acceleration to be carried out

prevails, part of these secondary electrons is therefore accelerated towards the plasma zone 1. They increase the electron density in the plasma. Due to the concavity of the front surface 17 of the extraction electrode 13 and the axial magnetic field maximum 7 in this area, the resulting electron beam 18 is strongly focused and constricted radially. The negative space charge of this electron beam 18 attracts the ions in the plasma and in the area between the plasma and extraction electrodes 12 and 13, so that the electron beam represents an extraction channel for the ions, which leads to an improvement in the emittance and brilliance of the extracted ion beam.

Another part of the secondary electrons with velocity components in the direction of the ion beam 16 runs with the ion beam and compensates for its space charge in the area 19 up to the next ion-optical component. This space charge compensation in region 19 largely prevents and prevents the Coulomb explosion of the very intense ion beam after the extraction thus also improving its emittance and brilliance.

1b and 1c show examples of evaporation containers 20. In this case, the cylinders are inserted axially into the plasma chamber 9 from behind. They are each supported by a jacket 21 and a heat-conducting tube 22 as an arm, which is connected at its rear end 23 to a heat sink (cooling) in order to generate a well-defined heat loss at the rear end of the evaporation container 20. The heat-conducting tube 22 is preferably made of copper. The closer the front end of the casing 21 and the evaporation tank 20 to the rear EZR zone 24, the more the front end of the evaporation tank 20 is heated, so that as a function of this approach a defined temperature gradient from the front to the rear part of the evaporation tank 20 can be observed or generated. In order to control this temperature gradient, one or more thermocouples 25 are attached along the evaporation container 20, which not only allow temperature reading, but also allow the axial, motorized feed of the evaporation container 20 to be controlled by means of an electronic control circuit in comparison with a setpoint temperature, as in FIG 1 schematically outlined. Using a corresponding servomotor or actuator

A corresponding signal can be generated via a differential amplifier (not shown).

The evaporation container 20 is shown in FIG. 1b as a closed container (first embodiment) with a small opening 26 for the steam outlet in the direction of the plasma. In FIG. 1c (second embodiment), it also has a second opening 27 at the rear end, through which an additional gas can flow through the evaporation container from behind during operation. Embodiment 2 (see FIGS. 2 and 2a)

FIG. 2 schematically shows a two-stage ion source device which doubles the principle of the CAPRICE type ion source according to FIG. 1. In a plasma chamber 9, two plasma zones 1 'and 1 "are formed with different pressures. The rear zone 1" has the higher pressure and therefore has a plasma zone with a lower mean state of charge in the plasma, while the front zone 1' has the lower pressure and therefore has a higher mean state of charge of the plasma in the plasma zone 1 '.

In order to maintain this pressure drop, the plasma chamber 9 is separated into the two areas by a differential pump aperture 30, which is partially transparent to the microwave. Pumping takes place on the (left) extraction side. The gas or vapor to be ionized is admitted from the rear (right). Technically, this ion source is realized in comparison to that in FIG. 1 by an elongated soft iron yoke 31, by three coils 32 and by two multipole permanent magnets 33.

As can be seen from FIG. 2a, the cylindrical wall of the extraction electrode 13, which is movable in the axial direction, is broken through in such a way that a heat-resistant, electrically insulating body 35, which is shaped in this way, can be fastened in the interior of the extraction electrode 13 in a fixed position 34 relative to the soft iron yoke 31 of the ion source and is drilled to allow wires to be clamped onto three electrically separated cone surfaces 36, 37, and 38. The wires can be clamped in a spiral or, as here, in planes parallel to the axes. A potential protection 39 on the isolating body 35 ensures that they run through it de ion beam 16 is always exposed to the potential of the extraction electrode. By charging with current and a negative voltage U _K , the wire of the cone surface 36 is heated and so this cone surface is used as a hot cathode grid for electron emission of the energy U _K eV. The wire on the cone surface 37 is charged to positive voltage U _A , so that a conical anode grid for the increased extraction of the electrons from the hot cathode grid with an electron energy of e • (| U _K | + | U _A |) eV takes place. The wire on the cone surface 38 is at the same potential U _E as the extraction electrode 13 and thus forms a conical brake grid, so that the electrons pass through this grid with the final energy e · U _K eV. In this way, an intensive electron emission of about 10 to 400 eV energy can be generated actively, concentrically around the ion beam and perpendicular to the conical lattice surfaces in such a way that the electron velocity vectors are approximately parallel or antiparallel to the magnetic stray field lines of the ion source if the opening angles of the conical ones Grids are adapted to the local magnetic lines. The electrons generated in this way follow the magnetic field lines into the plasma 1, where they converge on spiral paths around these magnetic field lines up to the maximum of the axial magnetic field to a minimum electron beam diameter and then diverge again and at the same time accelerate from the extraction electrode surface 17 to the plasma electrode 12 in the pulling field of the ions become. As a result, the ion beam 16 accelerated from the plasma is offered in the entire superimposed area by the electron beam 18 an extraction channel which compensates for space charge and which increases its brilliance. A cooling 28 of the extraction electrode 13 is provided in order to prevent the glu to dissipate heat developed.

So that the overlapping area of the ion beam 16 and the electron beam 18 fills the entire space close to the axis as far as possible up to the first ion-optical component, the electron generation described in FIG. 2a is attached as close as possible to this component in FIG. arranged at a great distance from the plasma electrode 12, where the magnetic stray field components of the ion source just outweigh other stray fields and thus ensure a well-defined electron beam. It should be noted that when generating electrons at such large distances from the plasma electrode 12, the concentric and rotationally symmetrical electron generation can be replaced by asymmetrical electron generation on one side of the axis if the magnetic guidance of the electrons ensures that the Electrons converge towards the axis of the ion source and, especially in the extraction area between the extraction electrode 13 and the plasma electrode 12 in the area near the axis, offer an extraction channel and a space charge compensation for the ions.

Embodiment 3 (see FIGS. 3, 3a, 3b and 3c)

3 shows a magnetic field configuration and the resulting axial magnetic field component 40 on the axis, in which the left magnetic field maximum 41 is generated by a current-carrying coil 42 and the right magnetic field maximum 43 by permanent magnets 44 arranged radially over the entire circumference, with a zero crossing of the field sign takes place. The same applies to the soft iron support of the overall arrangement as in exemplary embodiment 1, with the exception of the embedding of the radial permanent magnets 44. It consists of two concentric rings 45 and 46, the outside diameter of the outer (46) is equal to the outer diameter of the front soft iron disk 3a and the inner diameter of the inner (45) is adapted to the outer diameter of the plasma chamber insulation 10. A multiple of six radially magnetized permanent magnets 44 is arranged between the two rings 45 and 46 such that the polygonal outer diameter of the inner ring is fully equipped with permanent magnets. The permanent magnets 44 can have the shape of cuboids or trapezoids, they can also be replaced by a radially magnetized ring. With a corresponding variation of the other dimensions, one of the two soft iron rings 45 or 46 can be omitted.

Another special feature of this arrangement is that the soft iron disks 3d and 3e for the magnetic shunts towards the center of the ion source are thin

current-carrying coils 47 are occupied, so that the magnetic shunts can be changed by varying the current in these coils and thus the magnetic field minimum 52 during operation of the ion source.

The arrangement is completed by a permanent multipole magnet 53 for radial, magnetic confinement of the plasma.

As can be seen from FIG. 3a, electrons can be actively generated in the interior of the extraction electrode 13 on a cone jacket analogous to embodiment 2. In contrast to embodiment 2, the electrons are not generated here by glow emission, but with a so-called micropoint arrangement 48, as shown enlarged in FIG. 3a. Such a micropoint arrangement 48 consists of approximately 1 μm conical tips 49 at intervals of 10 μm, so that there are 10,000 micropoints per mm ² . Such a construction is known from the publications such as follows: CA Spindt, I. Brodie, L. Humphrey, and ER Westerberg, Journal of Applied Physics, Volume 47, page 5248 ff., 1976; CC Curtis and KC Hsieh, Review of Scientific Instruments, Volume 57, pages 989 ff., 1986; RE Mitchell, JBA Mitchell, and JW McGowan, Journal of Physics E, Volume 18, pages 1031 ff., 1985. Isolated from these cone tips, an anode matrix 50 is attached opposite them, on which a pulling voltage U _A of about 200 V compared to negative voltage of the cone tips U _{K is} applied. Due to the small dimensions, this relatively small voltage difference | U _A | + | U _K | is sufficient to draw 49 electron currents of up to about 0.1 μA from each cone tip by field emission, so that an electron current of up to 1 mA can be emitted per mm ² with negligible heat development. The electrons of the energy e · (| U _A | + | U _K |) are transferred to the potential U _{E of} the extraction electrode 13 by the brake grid cylinder 51 to the energy e · | U _K | decelerated so that a high density of electrons of low energy is generated in the region of the ion beam 16 between the electron generation 48 and the plasma electrode 12 for the space charge compensation of the ion beam and for the acceleration into the plasma 1.

3b, the electron generation described in FIG. 3a is placed as close as possible to this component, that is to say arranged at a great distance from the plasma electrode 12, so that the overlapping region of the ion beam 16 and electron beam 18 fills the entire space near the axis up to the first ion-optical component. where just the magnetic stray field components of the ion source outweigh other stray fields and thus ensure a well-defined electron beam. The opening angle of the Electron production cone is adapted to the direction of the magnetic stray field components in this area. In contrast to exemplary embodiment 1, the evaporation container 20 in this example is actively heated by a heating coil 54, as is shown enlarged in FIG. 3c. You will z. B. carried by a cylindrical ceramic holder 55 with a furrow spiral 56. Otherwise, all the essential features of exemplary embodiment 1 are obtained, as were explained with reference to FIGS. 1b and 1c. The current is supplied by a single supply line 57, because the return line is taken over by the conductive sheathing 21 of the ceramic cylinder 55 and by the heat-conducting carrier tube 22.

Embodiment 4 (see FIGS. 4 and 4a)

The exemplary embodiment according to FIG. 4 schematically shows an embodiment in which the front 60 (in the sketch on the left) and the rear magnetic field maximum 61 for the axial inclusion of the plasma 1 are generated by radially magnetized permanent magnets 62. The radial permanent magnets are embedded in concentric soft iron rings 63 and 64 for the front maximum and 65 and 66 for the rear maximum so that the polygonal outer diameter of the inner rings and the polygonal inner diameter of the outer rings are fully equipped with permanent magnets. The permanent magnets 62 can take the form of cuboids or

Trapezoids, they can also be replaced by a radially magnetized ring. With a corresponding variation of the other radial dimensions, either the outer or the inner soft iron ring can be omitted.

For the generation of magnetic shunts are as in Embodiments 1 and 3, the soft iron disks 3d and 3e provided, the interpretation of the depth of the

Determine magnetic field minimums 67 relative to the maxima 60 and 61. As in the exemplary embodiments 1 and 3, a soft iron cylinder 3c serves as a mechanical spacer and as the main magnetic circuit of the overall arrangement. A permanent multipole magnet 68 again ensures the magnetic radial confinement of the plasma 1.

In the axial direction, the soft iron rings and their fitting with radial permanent magnets on the extraction side (in the sketch on the left) are significantly longer than on the back of the ion source, with a ratio of 1: 0.8 to 1: 1.2 between the inner diameter of the inner ring 63 and its axial length is desirable. The resultant lower axial field gradient in the region of the zero crossing of the sign of the axial magnetic field component 69 (further simply called zero crossing) is used profitably for the arrangement of an active electron production which is concentric about the axis and takes place on a cone surface with a suitable opening angle, as shown in FIG 4a is shown enlarged. The electron generation with micropoints according to FIG. 3a of embodiment 3 is chosen in a double arrangement, mirror-symmetrical to the zero crossing, "once with the cone 70 opening towards the plasma and once with the cone 71 opening in the opposite direction. The two microdot cones with respective anode and brake grids 51 are carried by a common carrier body 72 made of any heat-resistant material (preferably ceramic) and centered exactly on the zero crossing, for this purpose the carrier body is mechanically fixed to the soft iron structure via a metallic cylinder 73, via insulation elements 74 and via a holder 75 connected to the ion source, the carrier body 72 and the Zy Linder 73 are electrically connected to the brake grids 51 and the extraction electrode 13.

This arrangement of electron generation compensates for the space charge of the ion beam 16 in the region from the zero crossing to the plasma electrode 12 by the electron beam 18 and in the region from the zero crossing to the next ion-optical component by the electron beam 76. The resulting improved brilliance of the ion source can be further optimized by varying the axial position of the plasma electrode 77 and independently of the extraction electrode 78. This is necessary because the electron generation and the magnetic field configuration are fixed in space and time by permanent magnets and therefore only these mechanical variations are available for optimization.

By choosing an evaporation arrangement with active heating according to FIG. 3c of embodiment 3, its position becomes independent of the rear resonance zone 24 and can therefore be attached easily accessible outside the ion source. As shown in FIG. 4, solid, vaporizable material is evaporated into the plasma 1 from the evaporation container 20 through a small steam opening 79 in the shield 80 of the microwave supply.

The microwave supply with its vacuum window 81 is schematically indicated here for longer microwave lengths with a Lecher line 82, the two conductors being shown next to one another in FIG. 4, but in reality are supposed to lie one behind the other.

Embodiment 5 (see FIGS. 5 and 5a)

The exemplary embodiment according to FIG. 5 schematically shows a magnetic field configuration equivalent to exemplary embodiment 4, as is evident from the similarity of the course of the FIG axial magnetic field component on the axis 90 with the course 69 shown in FIG. However, it differs significantly in that an iron-free design, which is only constructed with permanent magnets, is shown. The radially magnetized permanent magnet rings embedded in soft iron in FIG. 4 are arranged here in direct contact with the outer wall (including insulation and possible cooling) of the plasma chamber 91 to 93. The front ring, which is attached in the area of the extraction, is in two rings 92 and 93 divided, wherein the ring 92 can have a larger inner diameter than the ring 93, which are separated by a space 94, so as to bring about a minimum of the positive slope of the axial magnetic field component 90 in the region of the electron generation 95. Instead of the magnetic shunts in Figure 4, additional, radially magnetized permanent magnet rings 96 and 97 have to be attached here, which reduce the field of the permanent magnet main rings 91 to 93 to the center in such a way that their strength and position reduce the depth of the magnetic field minimum 98, relative to the front maximum 110 and to the rear maximum 111 of the magnetic mirror field. By axially displacing these rings 96 and 97 during operation of the ion source, this minimum and thus also the resonance zones can be displaced relative to the plasma electrode and the extraction of certain ions can be optimized. The composition of the radially magnetized permanent magnet rings can be carried out as in exemplary embodiment 4 or using adhesive technology. The axial magnetic structure is again supplemented by a permanent multipole magnet 99 for the radial confinement of the plasma 1.

The small axial field gradient caused by the gap 94 between the radially magnetized permanent magnet rings 92 and 93 at the zero crossing of the sign of the axial magnetic field component 90 (further simply called zero crossing) is analogous to FIGS. 4 and 4a is also used here profitably for the arrangement of active electron generation which is concentric about the axis and takes place on a cone surface with a suitable opening angle, as is shown enlarged in FIG. 5a. Electron generation with glow emission according to FIG. 2a of embodiment 2 is selected here in a double arrangement, mirror-symmetrical to the zero crossing, one with opening of the

Cone 100 to the plasma and once with the opening of the cone 101 in the opposite direction. The two glow emission cones 102 with respective anode 103 and brake grids 104 are carried by a common carrier body 105 made of any high-temperature-resistant material (preferably ceramic) and centered exactly on the zero crossing. For this purpose, the carrier body 105 is mechanically connected to the soft iron structure of the ion source via a metallic cylinder 106, via insulation elements 107 and via a holder 108, the carrier body 105 and the cylinder 106 being electrically connected to the brake grids 104 and the extraction electrode 13.

This arrangement of electron generation compensates for the space charge of the ion beam 16 in the region from the zero crossing to the plasma electrode 12 by the electron beam 18 and in the region from the zero crossing to the next ion-optical component by the electron beam 76. The resulting improved brilliance of the ion source can be further optimized by varying the axial position of the plasma electrode 77 and independently of the extraction electrode 78.

FIG. 5 also schematically shows how at the same time a plurality of evaporation containers 20, actively heated by heating coils and charged with different substances, outside the actual ion source body with the steam direction into the plasma 1 and with steam jet valves len 109 can be attached. It is thus possible to change the vapor material and recharge the evaporation containers while the ion source device is operating.

Sufficient free space remains between the alternating magnetic poles of the permanent magnet multipole 99 in order to be able to couple the microwave power with a rectangular waveguide 84 directly radially into the plasma chamber through a microwave-permeable vacuum window 85, the electric field vector of the microwave being perpendicular to the

Axis of the ion source device is and the coupling location can be freely selected between the permanent magnet rings 96 and 97. In this geometry, the incident microwave power can be coupled out again on the opposite one, or can be reflected in a manner adapted in such a way by a rectangular waveguide piece 86 with a movable closing piston 87 that a standing wave with a field maximum arises on the axis of the plasma chamber. The same standing microwave with a field maximum on the axis of the plasma chamber can also be achieved actively by symmetrically supplying two identical microwave powers with corresponding phase adaptation from above 84 and from below 86 in FIG. In this case, the rectangular waveguide 88 and thus also the microwave coupling can take place at angles other than 90 degrees to the axis of the plasma chamber, so that the field maximum not only on the axis but also e.g. is forced near the front resonance zone 89. With microwave supply from three radial directions offset by 120 degrees with corresponding phase adjustments of 120 degrees each, a maximum electrical field vector rotating about the ion source axis can be generated on the ion source axis.

The choice of the diameter of the metallic inner wall of the cylinder proves to be particularly advantageous drischen. Plasma chamber of approximately less than 0.59 of the wavelength of the microwave used. As a result, microwave resonances in the plasma chamber and thus not only unstable functional areas of the ion source, but also the axial microwave power transport to cyclotron resonance areas outside the multipole magnet are reduced. At the same time, with a microwave supply from one side, a standing microwave with an electric field maximum is almost achieved on the axis of the ion source by reflection on the opposite plasma chamber wall.

Embodiment 6 (see FIG. 6)

The exemplary embodiment 6 according to FIG. 6 shows schematically the braking of an ion beam 120 in a system of five pierced electrode disks 121 to 125, to which a magnetic field is superimposed with the aid of a coil 127 supported by a soft iron yoke 126. The ion beam 120, which originally comes from the right with 20q keV beam energy, is focused at point 128 and then passes through the five electrodes which are on the in

Figure 6 potentials are, and will be braked to the final energy of 1q keV and focused at point 129. q is the charge of the ions in the ion beam. The shape and the axial position of the course of the axial magnetic field component 130 shown are chosen so that the still high-energy ion beam enters the magnetic field in such a way that it experiences a strong inherent rotation due to the radial components of the increasing magnetic field 130 which are necessarily present and which emerge from the Magnetic field with lower energy is only partially reversed. 6, a well-defined self-rotation of the ion beam about its own axis is generated, which depends on the shape and the axial position of the magnetic field and the deceleration factor depend..

Through the choice of the sign of the magnetic field, the beam rotation generated in this way can be made the same in sign and strength in exactly the opposite direction as the beam's own rotation, as the ion beam 120 incident from the right has due to its acceleration of extraction from areas with radial magnetic field components of the ion source. The net result after the deceleration of the ion beam is therefore an ion beam 131 without self-rotation and thus an ion beam with better emittance and brilliance. It should also be noted

* that the extraction electrode (13) has a substantially cylindrical inner channel (15), in which preferably the inner diameter is about 2: 1 to 3: 1 to the length;

* that the inner channel (15) of the extraction electrode is preceded by a front surface (17) surrounding the inlet bore to the inner channel and concave towards the plasma chamber, which preferably has a radius of curvature which corresponds to three to five times the inner diameter of the inner channel (15);

* That ions, which diverge outwards at the periphery of the ion beam, generate secondary electrons on the wall of the inner channel (15), which on the one hand compensate for the space charge in the ion beam by axial velocity components in the direction of the ion beam and on the other hand between the extraction electrode and the plasma electrode by penetrating the extraction field in an electron beam can be bundled, which is accelerated into the plasma with the potential difference between the electrodes mentioned, so that that from the plasma coming ion current is space charge compensated and at the same time an extraction channel for ions is formed in the form of an electron beam from the EZR ion source to the extraction electrode, which is further amplified by secondary electrons which are generated by diverging parts of the ion beam on the concave front surface (17) of the extraction electrode;

* That seen in the ion beam direction behind the front surface (17) of the extraction electrode (13) mostly rotationally symmetrical about the ion beam axis electrons are generated and accelerated approximately tangentially to the magnetic stray field lines there (at low energies about 5 to 400 eV), which affect cyclotronic orbits these stray field lines and therefore along this

Move stray field lines and thus, like these, converge concentrically to the axis up to the front magnetic field maximum (7.41.60), so that a converging electron beam is formed which is well focused at the magnetic field maximum (7.41.60) and which corresponds to the potential difference between the Extraction and the plasma electrode (12) or (13) is accelerated into the plasma (1), so that the ion current (16) coming from the plasma is compensated for space charge and at the same time there is an extraction channel for the ions in the form of the electron beam (18) from the plasma to the extraction electrode (13);

* That the electrons are seen in the ion beam direction at a location at a greater distance behind the extraction electrode (13), so that the space charge compensation of the ion beam to a longer

Extend distance, provided that the magnetic stray field of the ion source at this location still dominates over other fields and that there is no zero crossing of the field sign from the field maximum of the extraction (7.41) to this location; * That the electrons are seen at a large distance behind the extraction electrode (13) when viewed in the direction of the ion beam, where the magnetic stray field of the ion source device is negligible and the electrons are generated asymmetrically, on one side of the ion beam axis in the form of a bundled beam and with the aid of a weak one magnetic auxiliary field can be directed to the axis and inside the ion source device.

* that the electrons are generated in the ion beam direction immediately before the location of a zero crossing of the sign of the magnetic stray field behind the front surface of the extraction electrode;

* That electrons are also seen and viewed in the ion beam direction immediately behind the location of a zero crossing of the field sign of the magnetic stray field behind the front surface of the extraction electrode approximately tangentially to the stray field lines present there (to low energy of about 5 to 400 eV), so that a forms with the ion beam accompanying electron beam, converging up to the secondary maximum of the stray field that necessarily occurs after a zero crossing and then diverging, but drawn by the positive ions, which compensates for the ion beam up to locations where other fields begin to dominate;

* that the electrons are generated by means of glow emission and accelerated to low energy or, if necessary, first accelerated and then decelerated again to low energy;

* that suitable heating wires for glow emission

are arranged concentrically around the ion source axis in the form of an emitting cone surface (36, 102) from which electrons can be extracted by means of a drawing voltage between the heating wires and a likewise concentric, conical anode grid (37, 103) spanned by fine wires;

* that the electrons can be braked to a low energy between the anode grid (37, 103) and a likewise concentric, conical brake grid (38, 104) spanned by fine wires;

* That the extraction electrode (13) is provided with a liquid cooling device (28) or with another form of heat dissipation;

* that micropoint surfaces (48) suitable for field emission are arranged concentrically and conically around the axis of the extraction electrode, from which electrons can be extracted by means of a drawing voltage between the micropoints (49) and the associated anode hole matrix (50);

* that between the microdot surfaces (48, 49) and their associated anode hole matrices (50) and a concentric, conical brake grid (51) spanned with fine wires, the electrons can be braked to a lower energy;

* That the plasma electrode (12) is axially displaceable relative to the plasma chamber (9) during operation of the ion source device;

* that the extraction electrode (13) is axially displaceable relative to the plasma electrode (12) during operation of the ion source device;

* that the entire magnetic structure (2, 3, 4; 31, 32, 33), the microwave supply (11), the plasma chamber (9), the The plasma electrode (12) and the electron generation (35-39) of the ion source device can be displaced axially relative to the extraction electrode during their operation, a bellows (14) ensuring the relative mobility and vacuum tightness;

* that the evaporation container (20) consists of heat-resistant material, is provided with a steam outlet opening (26), and with the help of a jacket (21) at the end of a heat-conducting arm (22)

is arranged, the other end (23) can be cooled and with which the evaporation container (20) with its casing (21) can be displaced in the vicinity of an EZR zone (24) located in the plasma chamber;

* that the arm is a thermally conductive tube (22), preferably of the same diameter as the casing (21) of the evaporation container (20);

* That the tube (22) and the sheath (21) at the same time the inner conductor of a waveguide for the

Are microwaves;

* that the evaporation container (20) is provided with at least one temperature sensor (25);

* that the axial position of the evaporation container (20) relative to the EZR zone (24) can be regulated by means of a servo device which can be controlled by signals from the temperature sensors (25);

* that the evaporation container (20) is provided with a heating device, preferably consisting of heating coil (s) (54);

* That the evaporation tank (20) is an evaporation cylinder made of a ceramic carrier cylinder the (55) is surrounded, which in turn carries the heating coil (54), and that the current is supplied via a wire (57) and the current is discharged via the casing (21) and the support arm designed as a tube (22);

* that several evaporation cylinders (20) are installed within the ion source device with steam direction in the plasma chamber (9), but separated from the plasma chamber (9) by vacuum valves (109);

* That the evaporation container (20) is provided in the direction of the support arm (22) with a gas flow opening (27);

* That the plasma chamber (9) of a two-stage ion source device is divided into two plasma areas (1 'and 1 ") by a perforated aperture that is as transparent as possible for microwaves and as tight as possible for gas, the plasma from the first area

(1 '') can diffuse into the second region (1 ') on the extraction side;

* That the plasma-enclosing magnetic field maximum (60) is generated on the extraction side with radially magnetized permanent magnets which are tightly packed between two soft iron rings (63) and (64), the inner diameter of the inner soft iron ring (62) being less than its length in the axial direction behaves as 1: 0.6;

* Ion source device according to claims 1 and 2 and 30, characterized in that the radially magnetized permanent magnets (62) packed between soft iron rings (63) and (64) are replaced by a radially magnetized permanent magnet ring with an outer soft iron ring, the inside diameter of the permanent magnet ring changing to its length as less than 1: 0. 6 behaves;

* that the soft iron support of the magnetic field generation in the interior is equipped with two soft iron disks (3d) or (3e) for the purpose of magnetic shunt, which are to be dimensioned so that the magnetic field minimum (6,52,67,98) the desired value relative to the magnetic field maxima (7.41.60.99) or (8.43.61.100);

* that the soft iron disks (3d) or (3e), which are installed for the purpose of magnetic shunt, are impressed with current-carrying coils (47), which allow the magnitude of the magnetic field minimum (6,52,67,98) relative to the magnetic field maxima ( 7.41, 60.99) or

(8,43,61,100) to vary during operation of the ion source device;

* That the maximum of the plasma-enclosing magnetic mirror field is generated on the extraction side with two, separated by an axial space, radially magnetized permanent magnet rings with the same or different field strength with the same or different inside diameters, which can also be composed of cuboid or trapezoidal individual magnets, the inside diameter the axial length of this double ring arrangement is less than 1: 0.8, so that a reduction of the axial magnetic field gradient is generated axially between the two rings for efficient electron production;

* that the arrangement claimed in claim 34 can be displaced axially during operation relative to the plasma chamber and to the plasma electrode fixed therein, so that the front electron cyclotron resonance zone can thereby be displaced relative to the plasma electrode and thus the ion yield can be optimized; * That the maximum of the plasma-enclosing magnetic mirror field on the side facing away from the extraction with a radially magnetized, during operation axially displaceable to the plasma chamber, permanent magnet ring, which can also be composed of cuboid or trapezoidal individual magnets, with an inner diameter that is the same or almost the same the outside diameter of the plasma chamber is to be produced, the inside diameter being less than 1: 0.6 relative to the axial length of this arrangement;

* that radially magnetized permanent magnet auxiliary rings with inner diameters slightly larger than the outer diameter of the multipole magnet near the two ends of this multipole magnet are so axially displaceable that their axial position, their polarity and their magnetization strength refer to the magnetic field minimum of the axial mirror field with respect to its absolute value, its relative value is determined on the front maximum of the mirror field and its axial position;

* That the microwave power directly with a rectangular waveguide between two poles of the permanent multipole magnet radially with electrical

Field vector perpendicular to the ion source axis is coupled into a plasma chamber, the metallic inner diameter of which is chosen to be less than 0.59 times the microwave length in a vacuum, so that the microwave is reflected on the cylinder wall opposite the coupling and thus a standing wave with maximum amplitude near the plasma chamber axis arises;

* that half of the microwave power is radially directly into the plasma chamber with two rectangular waveguides mounted radially symmetrically to the axis of the ion source between the poles of the permanent multipole magnet mer is coupled, the phase relationship of the two

Partial waves are chosen so that a standing microwave with a field maximum is formed on the ion source axis in the plasma range;

* that the microwave power to an Nth with N> 2 directly with N symmetrically around the

Rectangular waveguides attached to the ion source axis are radially coupled into the plasma chamber between the poles of the permanent multipole magnet, the phase position of the N partial waves being selected so that a standing microwave with an electric field maximum is formed on the ion source axis in the plasma region, the electric field vector of which rotates with the microwave frequency around the ion source axis ;

* the microwave power is coupled radially into the plasma chamber with rectangular waveguides between the poles of the permanent magnet dipole magnet, the axes of the rectangular waveguides taking an angle other than 90 degrees with respect to the axis of the ion source;

* that the plasma chamber is designed in the entire area of the magnetic structure as a continuous, metal-coated, microwave-transparent quartz or ceramic tube, which at the same time assumes the vacuum window function for the microwave supply;

* That the ion beam is braked at a great distance from its generation in an electrostatic electrode geometry known to those skilled in the art, which overlays an axial magnetic field (130) which is generated with a coil (127) with an iron yoke (126) or by permanent magnets with an iron yoke is that the existing self-rotation of the ion beam about its axis at Ab braking is eliminated;

* That the microwave power is directly coupled radially into the plasma chamber between two poles of the permanent multipole magnet and radially symmetrical to the axis of the ion source in a second rectangular waveguide connection, which is also between two poles of the permanent multipole magnet, is reflected on an adjustable piston surface, so that the phase the reflected wave can be adjusted so that a standing microwave with field maximum can form on the ion source axis.

Reference list

1, 1 ', 1' 'plasma zones 11 coaxial tube

2 coils 12 plasma electrode

3a -3f soft iron 13 extraction electrode

4 multipole magnet 14 bellows

5 magnetic field loss 15 extraction channel

6 magnetic field mini. 16 ion beam

7 magnetic field maxi. 17 concave front surface

8 magnetic field maxi. 18 electron beam

9 plasma chamber 19 space charge region

10 isolation circuit 20 evaporation container - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

21 sheathing

22 heat-conducting carrier tube

23 rear end of the support tube

24 rear EZR zone

25 thermocouples

26 steam opening

27 gas opening

28 Cooling - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

30 differential pump aperture

31 soft iron yoke

32 spools

33 multipole magnets

34 bracket

35 insulating body

36 cathode grid

37 anode grid

38 brake grille

39 Potential protection

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

40 Magnetic field profile 50 Anode matrix 41 Magnetic field maximum 51 Brake grid 42 Coil 52 Magnetic field minimum 43 Magnetic field maximum 53 Multipole magnet 44 Radial permanent magnet. 54 Heating winding 45 Soft iron inner ring 55 Ceramic body 46 Soft iron outer ring 56 Furrow spiral 47 Auxiliary coils 57 Power supply 48 Electron generation 49 Micropoint cone - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

60 front magnetic field maximum 61 rear magnetic field maximum

62 radial permanent mag.

63 front soft iron inner ring

64 front soft iron outer ring

65 rear soft iron inner ring

66 rear soft iron outer ring

67 magnetic field minimum

68 multipole magnet

69 Magnetic field course

70 electron generation cones

71 electron generation cone

72 carrier body

73 metal cylinders

74 isolator

75 bracket

76 electron beam

77 Plasma electrode shift

78 Extraction electrode shift

79 Steam opening

80 microwave shielding

81 vacuum windows

82 Lecher line

84 rectangular waveguide

85 vacuum windows

86 rectangular waveguide 87 reflection pistons

88 rectangular waveguide

89 Front resonance zone 90 Magnetic field

91 permanent magnet ring

92 "

93 "

94 space

95 Electron generation

96 permanent magnet ring

97 "

98 magnetic field minimum

99 multipole magnet

100 electron generation cones

101 "

102 glow emission cone

103 anode grid

104 brake grille

105 carrier body

106 metal cylinders

107 isolator

108 bracket

109 steam jet valve

110 front magnetic field maximum

111 rear magnetic field maximum

120 ion beam

121 electrode disc

122 ''

123 ''

124 ''

125 ''

126 soft iron yoke

127 coil

128 input focus

129 Initial focus

130 magnetic field profile

131 decelerated ion beam

Claims

Expectations:

1. A method for generating rays of any highly charged ions of low kinetic energy (about 1 to 200 eV per charge) with good brilliance

by generating and extracting the ions from a magnetically enclosed plasma contained in an ion source device, which is generated and heated by means of microwaves using the electron cyclotron resonance (EZR ion source),

with a plasma chamber (9) in which the vacuum required for plasma generation is generated and into which the microwaves are coupled,

with a plasma electrode (12) and an extraction electrode (13) through which the ions generated are extracted from the plasma, a high voltage difference (about 20 kV) between the plasma and the extraction electrodes (12) and (13) so-called electric pulling field is built up in a di- or converging magnetic field, in which the ion beam experiences an acceleration causing its own rotation around its axis,

characterized.

that the plasma chamber (9) is equipped with one or more material evaporator furnaces (20) which make it possible to generate plasmas and thus ions of any elements,

that the ion beam (16) coming from the plasma chamber (9) and passing through the plasma (12) and extraction electrode (13) is a electron beam (18) generated in the direction of the ion beam behind the extraction electrode front surface (17) and is electrically and magnetically focused near the ion beam axis above is stored and sent back that an electronic extraction channel with space charge compensation for the ions is formed,

that electron generation also takes place with velocity components parallel to the ion beam for the space charge compensation of the ion beam behind the location of the electron generation (19) and

that magnetic plasma confinement is achieved using suitable magnet configurations,

that with the aid of suitable microwave couplings into the plasma, a microfield amplitude is ensured at a sufficient height on the ion source axis, microwave resonances and thus piasma stability are to be avoided, and

that the self-rotation of the ion beam is reversed to the desired low energies by braking the ions in a magnetic field (120).

2. The method according to claim 1, characterized in that seen in the ion beam direction behind the front surface (17) of the extraction electrode (13) rotationally symmetrical about the ion beam axis generates and accelerates electrons approximately tangentially to the magnetic stray field lines there by means of glow emission with an adapted cooling device or by other methods are (at low energies about 5 to 400 eV), which move on cyclotron orbits around these stray field lines and therefore along these stray field lines and thus like this up to the front magnetic field maximum

(7,41,60,110) converge concentrically on the axis, so that a converging electron beam (18) is formed which is well focused at the magnetic field maximum (7,41,60,110) and which corresponds to the potential difference between the extraction and the plasma electrode (12 ) or (13) is accelerated into the plasma (1), so that the ion current (16) coming from the plasma is space charge compensated, and at the same time in the form of the electron Beam (18) an extraction channel for the ions from

Plasma (1) up to the extraction electrode (13).

3. The method according to claims 1 or 2, characterized in that the electrons seen in the ion beam direction immediately before the location of a zero crossing of the field sign of the magnetic stray field (69) behind the front surface (17) of the extraction electrode (13) are generated and that electrons immediately behind the location of this zero crossing, if necessary, are generated and accelerated rotationally symmetrically about the ion beam axis approximately tangentially to the stray field line present there (to low energy of about 5 to 50 eV), so that a moving along with the ion beam (16) up to after one Zero crossing necessarily occurring secondary maximum of the stray field converges and then diverges, but with the positive ions moving electron beam (76), which compensates for the ion beam up to places where other fields begin to dominate.

4. ion source device, suitable for carrying out the method according to claim 1 for the generation of rays of any uploaded ions of low kinetic energy (about 1 to 200 eV per charge) with good brilliance

with a plasma electrode (12) and an extraction electrode (13) through which the ions generated are extracted from the plasma, with high voltage difference (about 20 kV) between the plasma and the

Extraction electrode (12) or (13) a so-called electric pulling field is built up in a di- or converging magnetic field, in which the ion beam experiences an acceleration causing its own rotation about its axis,

characterized,

that the plasma chamber (9) is equipped with one or more material vaporizing furnaces (20) which make it possible to generate plasmas and thus ions of any elements, that that coming from the plasma chamber (9) and through the plasma (12) and extraction electrode ( 13) passing through an ion beam (16), viewed in the direction of the ion beam behind the extraction electrode front surface (17) and electrically and magnetically focused electron beam (18) is superimposed and sent in such a way that an electronic extraction channel with space charge compensation for the ions is formed, that electron generation also takes place with velocity components parallel to the ion beam for the space charge compensation of the ion beam behind the location of the electron generation (19) and that magnetic plasma confinement is achieved with the aid of suitable magnet configurations,

that with the aid of suitable microwave couplings into the plasma, a microfield amplitude is ensured at a sufficient height on the ion source axis, microwave resonances and thus plasma instabilities must be avoided, and that the ion beam's own rotation by braking the ions in a special magnetic field (120) on the targeted low energies is reversed.

5. ion source device for performing the method according to claims 1 and 2 and 3 and 4, characterized in that suitable for the field emission micropoint surfaces (48) are arranged concentrically and conically around the axis of the ion beam, from which by means of a drawing voltage between the micropoints (49) and the associated anode hole matrix (50), electrons are decelerated to a low energy by a brake grid (51), which is spanned concentrically and conically about the ion beam axis with fine wires and is mostly at the potential of the extraction electrode (13).

6. Ion source device according to claims 1 and 2, characterized in that the axial magnetic field maxima including the plasma (60,61) with a cylindrical soft iron yoke (3c), supplemented by soft iron disks (3d, 3e) with possible support by current-carrying coils (47) for the purpose of generating magnetic shunts, which allow the depths of the axial magnetic field minimum (67) to be determined, and with radially magnetized permanent magnet rings (62) or with tightly packed radially magnetized permanent magnets (62), which are produced between soft iron rings

(63,64) and (65,66) are packed, whereby the inner diameters of the inner soft iron rings (63,65) can have a length in the axial direction of 1: 0.5 to 1: 1.5 and the inner soft iron rings (63, 65) can be omitted in favor of the permanent magnet rings (62), the inner diameter of which is then adapted to the outer diameter of the plasma chamber.

7. ion source device according to claims 1 and 2 and 6, characterized in that the maxima

(110,111) of the axial magneti enclosing the plasma see mirror field with radially magnetized permanent magnet rings or tightly packed radially magnetized permanent magnets (91-93) with possibly inserted axial gaps (94), the inner diameter of the rings to their lengths in the axial direction as from 1: 0.5 to 1 : 1.5, and the minimum (98) of the axial magnetic mirror field enclosing the plasma by the axial distance of the permanent magnet rings (91-93) which can be changed during operation of the ion source and by two radially or axially magnetized permanent magnet rings or by tightly in Ring-shaped packed, radially or axially magnetized permanent magnets (96.97) with inner diameters somewhat larger than the outer diameter of the multi-pole magnet are determined, which are so axially displaceable near the two ends of this multipole magnet that during operation of the ion source by varying its axial Magnetic field minimum position (98) Both in terms of its absolute value and in terms of its axial position can be changed so that the plasma zone (1) can be influenced and axially displaced relative to the plasma electrode 12, which in this magnet configuration is in the region of the zero crossing by a second EZR resonance plasma zone (1 ') the axial magnetic field (90) in the middle of the rear permanent magnet ring (91) is supported, so that there is a real two-stage EZR ion source, the plasma zones (1 and 1 ''') of which are still partially separated by a microwave-permeable differential pump aperture (30) so that a pressure drop can be built up from the rear plasma zone (1 ') to the front plasma zone (1).

8. Ion source device according to claims 1 and 6 and 7, characterized in that the microwave power directly with a rectangular waveguide (84,86) through a vacuum-tight, microwave-transparent window (85) between two poles of the multipole magnet by radial, perpendicular or oblique to the plasma chamber axis, with an electric field vector perpendicular to the ion source axis in the plasma chamber, whose metallic inner diameter is to be chosen less than 0.50 times the microwave length in a vacuum, so that no microwave resonances can form in the plasma chamber and so that the Microwave is reflected on the opposite cylinder wall, and so a standing wave with maximum amplitude is generated near the plasma chamber axis.

9. Ion source device according to claims 1 and 2 and 7 and 8, characterized in that the microwave power directly with N rectangular waveguides with an angular distance of 2n / N around the plasma chamber axis through vacuum-tight, microwave-transparent window between the poles of the multipole magnet radially, with electrical Field vector perpendicular to the ion source axis are coupled into the plasma chamber, the power and the phase position of the N partial waves being chosen such that a standing, linearly polarized microwave with a field maximum forms on the ion source axis at N = 2 in the plasma chamber and at

N> 2 forms a standing, circularly polarized microwave with a field maximum on the ion source axis.

10. Ion source device according to claims 1 and 2 and 6 to 9, characterized in that the plasma chamber in the entire area of the magnetic structure is designed as a continuous, metallic sheathed, microwave-transparent quartz or ceramic tube, which also takes over the vacuum window function for the microwave supply at the points where the metallic cladding for the microwave rectangular waveguide

(84.86) is broken.

11. Ion source device according to one of the previous Henden claims, characterized in that the ion beam is braked at a great distance from its generation in an electrostatic electrode geometry known to the person skilled in the art, which has an axial magnetic field (120) connected to a coil (117) with an iron yoke (116) or by permanent magnets with an iron yoke is generated, is superimposed so that the existing self-rotation of the ion beam around its axis is eliminated when braking.