Abstract: A multi mode ion source is disclosed that includes an ion source incorporating an ionization chamber for ionizing gas species and configured to have at least two discrete modes of operation; namely, an arc-discharge mode and a non-arc discharge mode of operation.

Abstract: This invention relates to a method of producing a dopant gas species containing a required dopant element for implanting in a target and to an ion source for implementing such a method. In particular, although not exclusively, this invention relates to producing dopant ions for implanting in semiconductor wafers using an ion implanter. The present invention provides a method of producing a dopant gas species containing a required dopant element for implanting in a target, the method comprising: exposing a source mass of the element to gaseous bromine and element react to form a reactant product, and ionising the reactant product to produce ions of the dopant gas species.

Abstract: A cold-cathode closed-drift ion source includes an anode, a cathode and a power supply. In certain example embodiments, neither the positive nor negative terminals of the power supply are connected to ground, and the anode and cathode are also not connected to ground. Thus, the ion source operates in a floating mode. As a result, the likelihood of formation of a problematic secondary circuit from the source to the power supply through the walls can be reduced and/or eliminated (or suppressed). Therefore, the chance of drawing a net positive charge from the ion source which induces a positive charge on dielectric or other surfaces proximate the wall(s) can be suppressed and/or reduced.

Abstract: An rf ion source suitable for low power operation over a range of pressures in air which comprises discharge electrode, a cathode and an anode, the cathode being connected to an rf signal supply through an associated coupling means and the anode adapted to provide a surface area over which a plasma discharge may occur no greater than substantially that of the cathodal area over which the discharge may occur. The anode and cathode are arranged to be maneuverable with respect to one another in order to reduce the power requirements of the system and provide a means of controlling the rf discharge and ionization. An extended rf ion source, comprising a series of electrode pairs, provides flexibility for use in a variety of circumstances.

Abstract: An indirectly heated button cathode for use in the ion source of an ion implanter has a button member formed of a slug piece mounted in a collar piece. The slug piece is thermally insulated from the collar piece to enable it to operate at a higher temperature so that electron emission is enhanced and concentrated over the surface of the slug piece. The slug piece and collar piece can be both of tungsten. Instead the slug piece may be of tantalum to provide a lower thermionic work function. The resultant concentrated plasma in the ion source is effective to enhance the production of higher charge state ions, particularly P+++ for subsequent acceleration for high energy implantation.

Abstract: The invention relates to improving the efficiency of ion flow from an ion source, by reducing heat loss from the source both in the ion chamber of the ion source and its constituent parts (e.g. the electron source). This is achieved by lining the interior of the ion chamber and/or the exterior with heat reflective and/or heat insulating material and by formation of an indirectly heated cathode tube such that heat transfer along the tube and away from the ion chamber is restricted by the formation of slits in the tube. Efficiency of the ion source is further enhanced by impregnating and/or coating the front plate of the ion chamber with a material which comprises an element or compound thereof, the ions of which element are the same specie as those to be implanted into the substrate from the source thereof.

Abstract: An ion source includes an anode and/or cathode which is/are coated with a conductive coating. The coating has a sputtering yield less than that of an uncoated anode and/or cathode, so that erosion of the resulting anode and/or cathode in the source is reduced during source operation. Example coating materials for the anode and/or cathode of the ion beam source include metal borides including but not limited to TiB2 and ZrB2.

Abstract: Various aspects of the invention provide improved approaches and methods for efficiently:

Abstract: An arc chamber filament for an ion implanter used to implant ions in a semiconductor wafer substrate during the fabrication of integrated circuits on the substrate. The filament includes a pair of parallel filament segments each of which is connected to a voltage source at one end. The parallel filament segments are connected to each other through a bidirectional winding configuration which defines at least one generally U-shaped winding unit on each side of a plane of symmetry bisecting the filament.

Abstract: An ion source device includes an ion source having a filament for emitting thermoelectrons, a current measuring device for measuring current flowing through the filament, a voltage measuring device for measuring voltage across the filament, a resistance operation device for computing a resistance value of the filament by using the current and the voltage measured by the current and voltage measuring devices, and a prediction operation device for computing a time till the application limits of the filament or a time left till the application limits of the filament.

Abstract: The present invention relates to implementation of magnetic and electrostatic forces to guide ions along curved trajectories in an ion source such that macroparticles are separated from the ion stream. Magnetic and electrostatic fields act in concert with the present invention to cause ions to flow along curved trajectories from the arc source to an area where workpieces may be treated. Since macroparticles produced by consumable electrode sources are much less affected by magnetic and electrostatic fields, said macroparticles are able to be separated from the ion stream due to the curved trajectories followed by the ions. The present invention permits effective macroparticle filtering by incorporating a consumable electrode material that faces away from the workpieces and to a closed end of the ion source. This filtering technique allows separation of macroparticles from the ion stream without substantially compromising deposition area, deposition rate, ion transport efficiency and/or uniformity in coating.

Abstract: The invention relates to an ion source for an ion implanter in which source material for providing desired ions is provided in the form of a plate or liner which can be fitted into the reactant chamber of the ion source.

Abstract: An ion source for ionizing reactant gases in an ion implantation process for manufacturing semiconductor devices includes an arc chamber into which gas is supplied through a gas line, and a spray nozzle that is connected with the gas line. The spray nozzle has a plurality f minute spray openings that spray the gas flowing through the gas line uniformly into the arc chamber at a high velocity.

Abstract: The metastable atom bombardment source provides a charged particle free beam of metastable species that can be used to bombard and ionize organic and inorganic substances in a gas phase. The metastable atoms are produced by inducing a discharge in a gas (rare gases or small molecules). The discharge is curved between the cathode and anode, with the cathode located in a medium pressure zone and the anode located off-axis in a low pressure zone. A nozzle located between the cathode and the anode provides a collimated beam of metastable atoms of low kinetic energy that is directed at an ion volume containing the substances to be analyzed. By selecting the energy of the metastable state, selective fragmentation of molecules, particularly large molecular weight molecules, can be carried out.

Abstract: Methods and apparatus are provided for generating oxygen ions in an ion source having an arc chamber containing at least one oxidizable metal. The method includes the steps of feeding gaseous H2O into the arc chamber and operating the arc chamber in a temperature range where the free energy of formation of gaseous H2O is less than the free energy of formation of oxides of the oxidizable metal.

Abstract: The present invention relates to implementation of magnetic and electrostatic forces to guide ions along curved trajectories in an ion source such that macroparticles are separated from the ion stream. Magnetic and electrostatic fields act in concert with the present invention to cause ions to flow along curved trajectories from the arc source to an area where workpieces may be treated. Since macroparticles produced by consumable electrode sources are much less affected by magnetic and electrostatic fields, said macroparticles are able to be separated from the ion stream due to the curved trajectories followed by the ions. The present invention permits effective macroparticle filtering by incorporating a consumable electrode material that faces away from the workpieces and to a closed end of the ion source. This filtering technique allows separation of macroparticles from the ion stream without substantially compromising deposition area, deposition rate, ion transport efficiency and/or uniformity in coating.

Abstract: A liner (102) for an arc chamber (100) of an ion implanter. The arc chamber (100) comprises a liner (102) on the inner surface (104) of the arc chamber (100) that extends the life of the arc chamber (100). The liner (102) comprises a one piece portion (102a) that covers the bottom and long sidewalls of the arc chamber (100) and two end plates (102b) for covering the end walls of the arc chamber (100). When the liner (102) wears out it is replaced at a significantly reduced cost compared to replacing the entire arc chamber (100).

Abstract: An ion generator chamber, for an implantation apparatus, having its interior walls surfaces knurled or roughened so that any of the materials used in the chamber cannot deposit onto the interior wall surfaces in a size sufficiently large enough to adversely affect the operation of the chamber, if the deposits peel off the interior walls of the chamber. By limiting the size of any deposits on interior chamber walls, the invention extends the average life of the filaments used in the chamber as well as extending the average time between any necessary cleaning of the inner chamber walls thereby extending the operating life of the chamber.

Abstract: A cathodic arc plasma source has an anode formed of a plurality of spaced baffles which extend beyond the active cathode surface of the cathode. With the open baffle structure of the anode, most macroparticles pass through the gaps between the baffles and reflect off the baffles out of the plasma stream that enters a filter. Thus the anode not only has an electrical function but serves as a prefilter. The cathode has a small diameter, e.g. a rod of about ¼ inch (6.25 mm) diameter. Thus the plasma source output is well localized, even with cathode spot movement which is limited in area, so that it effectively couples into a miniaturized filter. With a small area cathode, the material eroded from the cathode needs to be replaced to maintain plasma production. Therefore, the source includes a cathode advancement or feed mechanism coupled to cathode rod. The cathode also requires a cooling mechanism.

Abstract: The invention provides methods and apparatus for generating helium ions. The methods involve providing a mixture of helium gas with a second gas in an ion source. The second gas has a lower ionization potential and larger molecules than that of helium. The helium gas is ionized by generating an arc discharge within the ion source. The presence of the second gas enhances the ionization of the helium gas. The increased helium ionization enables formation of helium ion beams having a high beam currents suitable for implantation.

Abstract: Ion source filaments, as well as methods and apparatus associated with the same are provided. The source filaments have a design that includes a relatively small surface area from which electrons are emitted (i.e., active portion) as compared to certain conventional source filaments. Suitable designs include filaments that have a V-shape or U-shape active portion, rather than a coiled active portion as in certain conventional source filaments. The source filaments of the present invention can increase the efficiency of ion generation and, in particular, the generation of multiply charged ionic species. The increased ion generation efficiency may enable formation of ion beams having relatively high beam currents suitable for implantation.

Abstract: A “triggerless” arc initiation method and apparatus is based on simply switching the arc supply voltage to the electrodes (anode and cathode). Neither a mechanical trigger electrode nor a high voltage flashover from a trigger electrode is required. A conducting path between the anode and cathode is provided, which allows a hot spot to form at a location where the path connects to the cathode. While the conductive path is eroded by the cathode spot action, plasma deposition ensures the ongoing repair of the conducting path. Arc initiation is achieved by simply applying the relatively low voltage of the arc power supply, e.g. 500 V-1 kV, with the insulator between the anode and cathode coated with a conducting layer and the current at the layer-cathode interface concentrated at one or a few contact points. The local power density at these contact points is sufficient for plasma production and thus arc initiation.

Abstract: According to the ion generation method, ion source material composed of an element of desired ions to be generated and I is heated so that vapor of the compound is generated, and the ions are generated by discharging the vapor. The iodide has no corrosiveness, and can be stably ionized. Further, it hardly reacts with oxygen or water and is safe.

Abstract: Ion implantation equipment is modified so as to provide a support ring between the filament and the cathode where it can continue its function of insulating the filament, thereby greatly extending the lifetime and reducing downtime of the equipment. According to the present invention, apparatus for preventing the short circuit of a filament of a source head to a cathode, comprising: an arc chamber, having an opening; a cathode tube, through the opening of the arc chamber extending in the arc chamber, one end of the cathode tube having a hollow, the hollow facing outside of the arc chamber; an isolated support ring, locating in the hollow's sidewall of the cathode tube; and a filament, through the isolated support ring locating in the cathode tube.

Abstract: An ion implanting architecture (60). The architecture comprises an arc chamber (64) having an interior area (64i). The architecture also comprises a plurality of electron sources (66, 68) disposed at least partially within the interior area. Each of the plurality of sources comprises a conductive plate (72, 80) operable to emit electrons into the interior area and a heating element (70, 78)for transferring heat to the conductive plate.

Abstract: An improved ion source head for use with an ion implantation machine includes an arc chamber within which a heated filament creates an ion plasma from a source gas. The source gas is introduced into the chamber evenly through at least four, but preferably six through hole openings in a bottom liner in the chamber. Even distribution of the gas entering the chamber reduces build-up and flaking of material in the chamber that can result in short circuits.

Abstract: A cold-cathode type ion-beam source with a closed-loop ion-emitting slit and electrons drifting in crosses electric and magnetic fields is characterized by the absence of a metal anode which is replaced by a pair of positively charged bodies, such as concentric rings of a conductive material which are located inside a hollow housing of the ion source and are connected to a source of a positive potential. The ion-emitting slit is located between these rings in an upstream position in the direction of propagation of the ion beam. Replacement of a metallic anode with an anodic plasma, i.e., with a “virtual anode”, which is formed by a Penning-type discharge, descreases contamination of the ion beam by products of erosion of a metallic anode and increases the ion beam current, which results in more effective ionization of the workout gas.

Abstract: The metastable atom bombardment source provides a charged particle free beam of metastable species that can be used to bombard and ionize organic and inorganic substances in a gas phase. The metastable atoms are produced by inducing a discharge in a gas (rare gases or small molecules). The discharge is curved between the cathode and anode, with the cathode located in a medium pressure zone and the anode located off-axis in a low pressure zone; A nozzle located between the cathode and the anode provides a collimated beam of metastable atoms of low kinetic energy that is directed at an ion volume containing the substances to be analyzed.

Abstract: An arc chamber including a reaction chamber, a filament element used to generate electrons, a first power supply means set for providing power to the filament element, a second power supply means utilized for creating a potential to increase the ionization efficiency, a plurality of gas injected openings set to inject suitable gas into the reaction chamber and be ionized in a gaseous plasma by impact from electrons, a first filament insulator, and three second filament insulators used for isolation. The first filament insulator includes a truncated corn portion and a ring portion. The truncated corn portion has a hole formed threrethrough itself. The ring portion is coaxially connected to the smaller surface of the truncated corn portion. The second filament insulator includes a truncated corn portion and two ring portions. Similarily, the truncated corn portion has a hole through formed therethrough. The ring portions are respectively coaxially connected to the two surfaces of the truncated corn portion.

Abstract: Ion implantation equipment is modified so as to provide filament reflectors to a filament inside of an arc chamber, and to remove the electrical insulators for the filament outside of the arc chamber and providing a means of shielding, thereby reducing the formation of a conductive layer on said insulators and greatly extending the lifetime and reducing downtime of the equipment. The efficiency of the equipment is further enhanced by means of an interchangeable liner for the arc chamber that increases the wall temperature of the arc chamber and thus the electron temperature. The use of tungsten parts inside the arc chamber, obtained either by making the arc chamber itself or portions thereof of tungsten, particularly the front plate having the exit aperture for the ion beam, or by inserting a removable tungsten liner therein, decreases contamination of the ion beam. Serviceability of the arc chamber is improved by means of a unitary clamp that separately grips both the filament and filament reflectors.

Abstract: An rf ion source suitable for low power operation over a range of pressures in air comprises discharge electrodes having one or more cathodes (1) and an anode (2). Each cathode (1) is connected to an rf signal supply (8) through an associated coupling means (4) and the anode (2) is adapted to provide a surface area over which a plasma discharge may occur that is not substantially greater than the total cathodal area over which the discharge may occur. In this way, the anode (2) presents no more useful surface than is required to accommodate the optimum area of the plasma discharge thereby preventing plasma wander and enhancing the stability of the discharge over known ion sources.

Abstract: A rectangular vacuum-arc plasma source and associated apparatus for generating and directing a stream of plasma containing an ionized vapor of a cathode material toward a substrate by vacuum arc evaporation of a rectangular planar cathode mounted in a rectangular plasma duct. The rectangular duct conducts the plasma from the cathode to the substrate region, while intercepting the molten droplets of cathode material also generated by the arc. Magnets control the arc motion on the cathode surface while simultaneously generating the magnetic field which guides the plasma through the duct. Benefits of a filtered cathodic arc (fully ionized vapor stream, elimination of splattered droplets) are combined with the benefits of a rectangular source (uniform evaporation from the source and uniform deposition on the substrate using linear motion). The rectangular source may be extended indefinitely in length, thus allowing coating or ion implantation on large or long substrates.

Abstract: An ion generation device includes a chamber in which plasma is generated, a first opening for introducing gas to be ionized by the plasma, and a second opening for irradiating ions generated from the gas. The inner wall of the chamber is coated with metal which is resistant to chemical etching by the ions and radicals.

Abstract: An improved ion source assembly in an ion implant machine is provided that can withstand thermal stress and remain gas leak proof. The ion source assembly is comprised of a vaporizer with a tubular conduit at one end, a fitting, and an arc chamber. The improvement being leak-proof connections: (1) between the conduit and the fitting and (2) between the fitting and an arc chamber. The fitting has a chamber through the center. The chamber has a larger diameter at the back end than at the front end and a central tapered portion connecting the front end and back end portions. The conduit is fit into the back end of the chamber thereby forming a first gas leak proof connection. The fitting has an outer tapered from end portion and the arc chamber has a tapered opening. The tapered front end of the fitting engages the tapered opening of the arc chamber forming a second gas leak proof connection thereby providing a gas leak proof ion source assembly.

Abstract: Ion implantation equipment is modified so as to provide filament reflectors to a filament inside of an arc chamber, and to remove the electrical insulators for the filament outside of the arc chamber and providing a shield, thereby reducing the formation of a conductive layer on said insulators and greatly extending the lifetime and reducing downtime of the equipment. The efficiency of the equipment is further enhanced by an interchangeable liner for the arc chamber that increases the wall temperature of the arc chamber and thus the electron temperature. The use of tungsten parts inside the arc chamber, obtained either by making the arc chamber itself or portions thereof of tungsten, particularly the front plate having the exit aperture for the ion beam, or by inserting a removable tungsten liner therein, decreases contamination of the ion beam. Serviceability of the arc chamber is improved by using a unitary clamp that separately grips both the filament and filament reflectors.

Abstract: Ion implantation equipment is modified so as to provide filament reflectors to a filament inside of an arc chamber, and to remove the electrical insulators for the filament outside of the arc chamber and providing a means of shielding, thereby reducing the formation of a conductive layer on said insulators and greatly extending the lifetime and reducing downtime of the equipment. The efficiency of the equipment is further enhanced by means of an interchangeable liner for the arc chamber that increases the wall temperature of the arc chamber and thus the electron temperature. The use of tungsten parts inside the arc chamber, obtained either by making the arc chamber itself or portions thereof of tungsten, particularly the front plate having the exit aperture for the ion beam, or by inserting a removable tungsten liner therein, decreases contamination of the ion beam. Serviceability of the arc chamber is improved by means of a unitary clamp that separately grips both the filament and filament reflectors.

Abstract: A method for treatment of products in gas-discharge plasma consists in that a two-step vacuum-arc discharge is initiated between an anode (3) and an integrally cold cathode (2), featuring a metal-gaseous step of plasma and a gaseous step of plasma. The gaseous step of plasma is established by ionizing the working gas with electrons separated from the metal-gaseous step of plasma. Then a product (5) under treatment is preheated to working temperature and held in a preset temperature range. To this end, provision is made in the device for a means (13) for electron separation from the metal-gaseous step of plasma, which means is situated in the zone of the integrally cold cathode (2) and is impermeable to the metal ions generated by the cathode (2). In a particular case the means (13) is made as a set of V-shaped plates (14).

Abstract: The invention relates to a method and a generator for producing an aluminum ion flow, specifically for aluminum ion implantation in the microelectronics industry.

Abstract: A rectangular vacuum-arc plasma source and associated apparatus for generating and directing a stream of plasma containing an ionized vapor of a cathode material toward a substrate by vacuum arc evaporation of a rectangular planar cathode mounted in a rectangular plasma duct. The rectangular duct conducts the plasma from the cathode to the substrate region, while intercepting the molten droplets of cathode material also generated by the arc. Magnets control the arc motion on the cathode surface while simultaneously generating the magnetic field which guides the plasma through the duct. Benefits of a filtered cathodic arc (fully ionized vapor stream, elimination of splattered droplets) are combined with the benefits of a rectangular source (uniform evaporation from the source and uniform deposition on the substrate using linear motion). The rectangular source may be extended indefinitely in length, thus allowing coating or ion implantation on large or long substrates.

Abstract: A magnetic-cusp for a cathodic-arc source wherein the arc is confined to the desired cathode surface, provides a current path for electrons from the cathode to the anode, and utilizes electric and magnetic fields to guide ions from the cathode to a point of use, such as substrates to be coated. The magnetic-cusp insures arc stability by an easy magnetic path from anode to cathode, while the straight-through arrangement leads to high ion transmission.

Abstract: An arc source macroparticle filter (1) includes a circular cathode (2) for emitting particles and an extended cylindrical anode (3) adjacent to and co-axial with the cathode for accelerating the emitted particles. Toroids (4) generate a magnetic field to define a continuous non-linear plasma duct (5) for directing charged particles and separating therefrom undesirable larger particles. The duct is minimally non-linear to permit high rates of charged particle transmission. Arc source filter (1) allows heating and/or the deposition of a variety of surface coatings to a workpiece (8).

Abstract: A cylindrically symmetric arc source to produce a ring of ions which leave the surface of the arc target radially and are reflected by electrostatic fields present in the source to a point of use, such as a part to be coated. An array of electrically isolated rings positioned in the source serves the dual purpose of minimizing bouncing of macroparticles and providing electrical insulation to maximize the electric field gradients within the source. The source also includes a series of baffles which function as a filtering or trapping mechanism for any macroparticles.

Abstract: A continuous, cathodic arc ion source coupled to a macro-particle filter capable of separation or elimination of macro-particles from the ion flux produced by cathodic arc discharge. The ion source employs an axial magnetic field on a cathode (target) having tapered sides to confine the arc, thereby providing high target material utilization. A bent magnetic field is used to guide the metal ions from the target to the part to be coated. The macro-particle filter consists of two straight solenoids, end to end, but placed at 45.degree. to one another, which prevents line-of-sight from the arc spot on the target to the parts to be coated, yet provides a path for ions and electrons to flow, and includes a series of baffles for trapping the macro-particles.

Abstract: Ion implantation equipment is modified so as to provide filament reflectors to a filament inside of an arc chamber, and to remove the electrical insulators for the filament outside of the arc chamber and providing a means of shielding, thereby reducing the formation of a conductive layer on said insulators and greatly extending the lifetime and reducing downtime of the equipment. The efficiency of the equipment is further enhanced by means of an interchangeable liner for the arc chamber that increases the wall temperature of the arc chamber and thus the electron temperature. The use of tungsten parts inside the arc chamber, obtained either by making the arc chamber itself or portions thereof of tungsten, particularly the front plate having the exit aperture for the ion beam, or by inserting a removable tungsten liner therein, decreases contamination of the ion beam. Serviceability of the arc chamber is improved by means of a unitary clamp that separately grips both the filament and filament reflectors.

Abstract: A plasma generating device includes a central conductor, a peripheral cylindrical conductor surrounding the central conductor, an insulating cylinder interposed between the central conductor and the peripheral conductor in order to prevent direct arc discharge from occurring between the central conductor and the peripheral conductor. The central and peripheral conductors and the insulating cylinder are coaxially arranged in order to define a cylindrical discharging space therein. By applying a high frequency energy to the central conductor, glow discharge is caused between the central and peripheral conductors. A reactive gas is introduced from one end of the discharging space, excited by the glow discharge and goes out from the other end as an excited plasma to a working place where a work piece is processed by the plasma.

Abstract: The device comprises a cylindrical casing provided with an internal cavity and with a flange and an arc chamber superimposed over the cylindrical casing and including a filament electrically supplied through supply conductors external to said casing and supported by said flange, a repeller plate held at a negative voltage through supply conductors external to said casing and supported by said flange and an inlet for a gas which may be ionized, Inside the arc chamber there is also a support for the metal to be ionized supported and connected electrically to an electrode at a negative voltage by means of a rod passing through the internal cavity of said cylindrical casing.

Abstract: An ion generating apparatus utilizing a vacuum chamber with an anode and multiple, selectively operable, cathodes in the chamber. The vacuum chamber is grounded and all but the cathode or cathodes selected for use are grounded to the chamber. The anode is a high-transparency screen, preferably formed from a copper alloy. The cathodes are preferably arranged in a generally circular array, parallel to each other, so that any can be fired by a single trigger cathode assembly positioned adjacent to the array. A linear feed mechanism for moving any cathode toward the anode as cathode material is consumed may be provided.

Abstract: A vacuum arc ion source comprises an anode (2 or 3) and a cathode (1) which face each other and whose plasma (7) is emitted perpendicularly to the cathode surface. The projection of this plasma is obtained by means of two independent appropriately biased grids (4 and 5).

Abstract: An apparatus for generating negatively charged species has a cathode and an anode which are disposed in a vacuum vessel facing each other. A constricted arc having a sufficiently large arc current is generated in an arc space between the anode and the cathode, thereby generating negatively charged species of various types of metals, semiconductors, and gases.

Abstract: A hollow cathode ion source for in a vacuum chamber wherein it comprises a cylindrical cathode through one end of which a gaseous medium of at least a discharge maintaining gas or said discharge maintaining gas and a metal vapor is or are introduced, and an anode provided on the other end of said cylindrical cathode and having at least one ion extraction opening, said gaseous medium being ionized by a discharge means between said cylindrical cathode and said anode to produce ions which are extracted through said ion extraction opening in the axial direction of said cylindrical cathode.The cylindrical cathode in the ion source has a large diameter at least about half and preferably about equal to its axial length and may be directly cooled.