DE1222589B - Device for generating a space-charge-neutralized beam of charged particles - Google Patents

Description

Device for generating a space-charge-neutralized beam charged particles The invention relates to a device for generating a space-charge-neutralized particle Beam of charged particles with an ion source and a source of high energy Electrons arranged next to each other on a common symmetry and beam axis are.

It is known to effect space charge neutralization by an electron source is provided close to the exit of the ion source to produce a die To generate ions surrounding electron cloud. It is due to the changes in ion density difficult to always have the right amount and the appropriate spatial distribution of electrons to obtain. In addition, the plasma oscillations due to the non-uniform distribution of electrons be generated transversely to the ion exit beam. Also takes place with a space charge neutralization at the exit end of the ions from the ion source and only after its acceleration no complete neutralization takes place within the device. Therefore, Before the acceleration takes place, space charge forces occur in the device and limit the ion current so that low-momentum ions are generated. The impulse of the neutralized beam is important when using the present ion source for the ion propulsion of a spaceship. When the space charge is not completely neutralized the thrust that can be achieved with the ion drive is small.

It is known that there are great difficulties due to the space charge effect can occur as a result of an electrostatic expansion of the ion beam good focus is prevented. Plasma physics has many applications for which a high current ion source with a defined ion beam is desirable. In addition to the use of such an ion source for the ion propulsion of spacecraft, mentioned above, another preferred area of application is injection of ions in devices that are used to generate a high-energy plasma for the Neutron generation are suitable. Another use for an ion source is ion injection in experimental set-ups to investigate the possibility of controlled thermonuclear Study reactions.

A vacuum vessel is known in which both canal rays and Cathode rays are generated and directed against a Lenard window. At this known arrangement is in a space which is penetrated by canal rays, a Hot cathode, which emits electrons, arranged. A space charge neutralization of the canal rays takes place only partially. The well-known vacuum vessel is used to carry out chemical reactions, with an air stream beyond the Lenard window is passed by.

In view of the limitations imposed by prior art ion sources are subject to the technology and in contrast to the latter known Arrangement in which the space charge compensation takes place partially in a vacuum vessel, is the main object of the present invention in the generation of a directed, completely space-charge-neutralized ion beam, which is used, for example, as a drive can be used for a spaceship.

A device for generating a space-charge-neutralized, directed beam of charged particles created in accordance with the invention the electron beam is directed in the direction of the ion beam by the ion source and the ion extraction electrode passes through and a common magnetic Guiding field for the ion and electron source is provided, whose lines of force are directed parallel to the common ray and symmetry axis.

The invention is explained in more detail, for example, using the figures. F. i g.1 shows schematically a device for generating a space charge neutralized Charged particle beam, consisting of an electron-ion source combination; F i g. 2 shows a section through an injector device in which the ion source and the electron accelerator shown in Fig.1 for the generation an energetic, neutralized beam of electrons and ions is used will; F i g. 3 shows a section of an injector device in which the FIG. 1 illustrated particle source for generating a neutral high density plasma is used; - F i g. 4 shows a schematic view of a particle source, which can be used as a propulsion system for spaceships; F i g. 5 shows a schematic View of another embodiment of a drive for spaceships.

This task is accomplished with a gas-charged arc discharge for ion generation and solved with an electron source that is a controlled shoots a monoenergetic electron beam through the arc discharge. This will an intimate mixture of accelerated ions and electrons within the ion source and beyond the ion source and an effective neutralization of the space charge is achieved. The space charge neutralization in the ion source and in the acceleration gap is caused by oscillating electrons of low energy and space charge neutralization in the beam that has emerged from the ion source is caused by the monoenergetic Electron flow caused beyond the occurrence-side end of the ion source. Of the neutralized beam can be accelerated to any desired energy in a density that is well above the limit of what has been achieved so far. The electron ion source is well suited for the propulsion of spaceships, because of the space charge neutralization the spacecraft is prevented from charging. If one of the usual ion sources is used on the spacecraft, the ions can pass through after a certain time the charge of the spaceship will be attracted to it; and the drive system becomes ineffective.

The high-energy electrons in the particle source shown in FIG. 1 are generated with an electron accelerator, which is described below. A cathode 1, which can be heated either directly or indirectly, is arranged with a hollow anode 2 open on both sides on a common axis of symmetry. A gas, for example argon, is passed from a gas source 4 into the interior of the anode 2 via the line 3. A direct current source 5 with a voltage of 150V is connected between the cathode 1 and anode 2 by means of lines 6 and 7. A gas discharge is ignited between the cathode 1 and the anode 2. The direct voltage potential of 150 V is applied to the small plasma layer that is formed by the plasma arc on the surface of the filament cathode. In this way the electrons are in an electric field with a very steep field gradient. This arrangement enables ions formed by the arc discharge to neutralize space charge forces, whereby a dense electron stream 11 can be obtained and passed through the anode 2 using a suitable accelerating potential. The electron gun is located in a strong axial magnetic field of about 6000 Gauss, which is generated by magnetic coils, not shown, so that the electron stream 11 is sharply focused. The direction of the magnetic field is indicated by the arrow H: A high-voltage shield 8 surrounds the electron gun. The shielding increases the efficiency of the electron centrifuge and reduces the difficulties caused by electrical breakdown at high acceleration voltages. An acceleration electrode 10 is provided immediately after the shield 8 and is electrically connected to this shield 8 by a line 9. The shield 8 and the electrode 10 are connected to a high voltage source of about 39 to 43 kV, which potential with respect to the ion source is negative, as will be described below.

The electron spinner creates a parallel electron beam with a maximum energy of 5 keV, a current of 1 A and with a diameter of 0.635 cm. This corresponds to a particle density of 5.1010 / cm2 or one Current density 5 A / cm2.

The arrangement for generating the ions will now be described in the manner shown in FIG. 1 described device shown. A hollow cylindrical tungsten cathode 16 is fastened in an end plate 12. A hollow cylindrical anode 17 is located in a tubular part 14. The part 14 is flanged at each end. An annular insulator 13 is disposed between the end plate 12 and an end flange of the part 14 . An annular shield 15 surrounding the cathode 16 is located within the annular insulator 13. The portion 14 is provided with an inner, enlarged portion which tightly encloses the anode 16, as shown, to prevent ions from escaping from the Arc discharge into the space in which the shield 15 is located. The cathode 16 and the anode 17 are arranged coaxially with the electrodes of the electron gun. An annular end plate 20 with a tungsten insert 21 is mounted on the outer end flange of the part 14. The plates 12 and 20 are connected to direct current sources (not shown) with voltages of 99.85 and 100 keV, respectively. An annular electrode 22 is disposed beyond the end plate 20. This electrode 22 is arranged in an insulated manner, and therefore its electrical potential is indeterminate. The gas, which can be, for example, deuterium, is conducted from a source 19 via a tube 18 to the interior of the anode 17 . A reverse gas discharge arc 23 is ignited between the cathode 16 and the anode 17 in the manner. The axial magnetic field of 6000 Gauss in which the electron ejector is located also includes the ion source. The electron gun and the ion source are both enclosed in a chamber (not shown) which is evacuated to a pressure of about 3.10-5 mm Hg. The ion source generates an ion beam with a current of 0.5 A and an energy of 6 keV using deuterium as the gas. The energetic electrons 11 from the electron source are shot through the center of the return current discharge arc 23. There is an intimate mixture of the accelerated ions and the electrons within the zone source and the acceleration gap as a result of the electron oscillations within the source and also an intimate mixture of the accelerated ions and the accelerated electrons beyond the exit end of the ion source, since energetic electrons in the exiting ones Zone beam arrive. In this way, an effective space charge neutralization is brought about within and after the zone source. An accelerating electrode 24, which is grounded, is provided through end plate 20 and electrode 22 for drawing the ions from the source. Some of the electrons from the high-energy electron stream 11 will reach the acceleration electrode and have sufficient energy to flow out through this electrode together with the ions from the zone source and thereby generate a neutralized beam 25 of electrons and ions. Because the space charge neutralization is created within the arc gap, the output current of the beam 25 is substantially greater than that obtained with a conventional zone source, since the emission from a conventional zone source is limited by the space charge forces. The insulated electrode 22 is used as a shield electrode, and it has been found that the arrangement of this electrode also increases the output current of the neutralized beam 25. The relatively cold electrons of the arc discharge 23 and those of the high-energy beam 11, which are slowed down by impact processes, do not have sufficient energy to be passed through the electrode 24, since this electrode reflects the electrons with low energy. These electrons oscillate between the electrode 24 and the cathode 16. The oscillating electrons are used for the space charge neutralization within the zone source and the acceleration gap, as explained above. It is found that the electrons and ions in the zone source are exposed to the same magnetic and electrostatic fields. By appropriately controlling the density of the entire electron flow, the resulting beam is always neutralized. Space charge neutralization takes place within the zone source and in the acceleration gap as well as beyond the acceleration electrode.

The neutralized beam of an arrangement according to FIG. 1 can be used for one Injector used to transfer the beam into a neutron generating plasma device to inject. To obtain a high density plasma in such a device, the density of the injected ions should be as great as possible, for example about 109 / cm3 at 600 keV. When using the device shown in F i g.1 for such an injector it is possible to obtain such a density that on the other hand impossible to achieve with conventional zone sources, since the electrostatic Forces resulting from the space charges drive the beam apart. F i G. Figure 2 shows how the zone source in Figure 1 applies to a neutralized beam injecting injector can be used. An electron supply tube 27 carries an indirectly heated thread electrode 28, which is axially spaced from a hollow anode 29 open on both sides is arranged. The electron flow 50 from the electron source is driven by a plurality of ring-shaped electromagnetic coils 52, 53, 54, 55 and 56, then by the zone source described below a plurality of solenoids 58, 59, 60 and 61 and finally by a shielded Injection tube 49 passed. The zone source is enclosed by a magnetic coil 57. The coils 52 to 61 act as collimator coils, the field strength of which is about 6000 Gauss in the center of the coil and about 2000 Gauss in the gap between the individual coils amounts to. The direction of the field is indicated by the arrow H.

The in F i g. The device shown in FIG. 2 is in a vacuum chamber 30 included. This chamber 30 is made up of part 31, an annular plate 32, a tubular insulation 33, an annular plate 38, a tube 63, a Ring plate 40, a tubular insulation 41, a ring plate 46 and a Vacuum nozzle 47 is formed. The part 31 is connected to two vacuum pumps 26 and 26 '. The vacuum port 47 is connected to two vacuum pumps 48 and 48 '. The chamber 30 is pressurized by the pumps 26, 26 ', 48, 48' to a pressure of about 3 - 10-5 mm Hg evacuated.

The coils 52 to 56 and 58 to 61 are enclosed in metal housings. The housings around the coils 52 and 53 are connected to zero potential by means of electrical Lines that are not shown connected. The casing around the coils 54, 55 and 56 are via parts 34 and 35 and electrical lines, not shown connected with direct voltage waves of 150, 300 and 450 kV. The top and Lower plates of the zone source are via portions 38 and 40 and not shown electrical lines connected to DC voltage sources of 599.85 and 600 kV. The housings around the coils 58, 59 and 60 are via parts 42 and 43 and electrical Lines (not shown) with direct voltage sources of 450, 300 and 150 kV tied together. The housing around the coil 61 is at the zero potential by means of not shown Lines connected. A shield 62 is placed at the output end of the coil 61, to ensure that the electron ion beam 51 enters the injector tube 49.

The voltage drop between the coils 53 to 56 accelerates the Electrons from the electron source first, and the voltage drop between the Coils 58-61 decelerate the electrons after they have passed through the zone source became. The voltage drop between the coils 58 to 61, on the other hand, accelerates the ions from the zone source, so that the beam 51 is made up of electrons and ions ejected from tube 49 at a substantially homogeneous rate.

This beam 51 will be essentially space charge neutralized. To prevent the potential differences between the coils, the insulating Parts 33 and 41 penetrate, shields 36 are above the zone source for Protective part 33 and shields 44 below the zone source for protection of part 41 is provided.

The zone source of FIG. 2 has a hollow cylindrical cathode 65, a hollow cylindrical anode 66 and an accelerating electrode 64. The gas is fed into the interior of the anode 66 through a feed pipe 67. The accelerating electrode 64 is connected to an accelerating voltage source, not shown, of FIG about 560 kV connected. the Electrodes 28, 29, 65, 66 and 64, the Coils 52 to 56, coils 58 to 61 and tube 49 are all in axial alignment arranged around a common axis, and this axis is parallel to the direction of the magnetic field H.

An arc discharge is generated in the ion source as shown in FIG. 2 shown is obtained in the same way as in connection with FIG. 1 described became. The density of the electron stream `50 is controlled so that substantially a complete space charge neutralization of the exit beam 51 takes place. Therefore, the in FIG. 2 device shown a high-energy neutralized Beam of electrons and ions. The in F i g. The injector shown in FIG. 2 is special for the injection of two or more kinds of molecular ions into plasma devices capable of generating ions. Since the beam in FIG. 2 over the entire length of the Injector runs straight, both diatomic and triatomic ions, which are generated in the ion source, at the same time in such plasma devices injected.

It may be desirable to have a neutralized jet plasma injector higher density. This can be done by eliminating some of the acceleration and delay stages shown in FIG. 2, as well as by use lower acceleration and deceleration voltages. be enough. One such a device is shown in FIG. 3 shown. A tube 85 that has an indirectly heated Thread electrode 86 carries is arranged in an end plate 72. A hollow cylindrical one Anode 87 is arranged at a distance from the thread electrode 86 and coaxially therewith. The electron source generates an electron beam 74. The figures shown in FIG. 3 shown Ion source has an annular end plate 91, in .der a hollow cylindrical Cathode 82 is held .. a hollow cylindrical anode 83, which is connected to a gas source connected via a supply line 84, an annular end plate 92, a Accelerating electrode 71 and a solenoid 89 that form the cathode 82 and the anode 83 surrounds. A magnetic coil 88 is attached to the plate 72 and surrounds the thread cathode 86 and the anode 87 of the electron source. The space between the coil 88 and the End plate 91 is enclosed by an annular shield 77. A solenoid 90 is arranged at an axial distance from the acceleration electrode '71 and on attached to the end plate 73. The space between the coil 90 and the plate 92 becomes of an annular shield 76 um-_. The coils 88, 89 and 90 generate a collimator magnetic field; the direction of which is indicated by the arrow H. and its field strength about 6000 Gauss in the center of the coil and about 2000 Gauss in the Gaps between the coils is. The electrodes 86 and 87, 82, 83 and 71 and the coils 88, 89 and 90 are coaxially arranged, and this axis runs parallel to the direction of the magnetic field H.

A part 78 is firmly connected to the plate 72 and a part 79 to the plate 91. These parts 78 and 79 are flanged as shown to form openings which are connected to vacuum pumps, not shown. A part 80 is connected to the plate 92 and a part 81 to the plate 73. These parts 80 and 81 are flanged as shown to form openings which communicate with vacuum pumps (not shown). The space within the device shown in FIG. 3 is evacuated by these pumps to a pressure of about 3 - 10-5 mm Hg. The plates 72 and 73 are held at zero potential by means of devices not shown. The plates 91 and 92 are connected to voltage sources of about 99.85 and 100 kV by means of lines not shown, and the accelerating electrode 71 is connected to a voltage source by means of devices not shown of about 60 kV.

The device shown in FIG. 3 operates in the same way as that in Fig. 2, except that much lower acceleration and deceleration potentials can be used. The resulting Beam 75 of electrons and ions is essentially completely neutralized in space charge and has a much higher density than with the device shown in F i g. 2 is shown, can be generated. By creating a neutral High density plasmas make it possible to create such a plasma across the magnetic field lines to inject into a device designed to generate a very dense plasma 1 is used for neutron production.

A neutralized electron-ion beam can be in a variable Thrust system used for propulsion of spacecraft. Such an arrangement is in Fig. 4 shown. These in FIG. 4 shown device is the similar to those shown in Fig. 1, except that a different electron source is used. In the case of the in FIG. 4 shown electron source is a hollow cylindrical Cathode 98 is arranged in a carrier part 97. Gas is passed through from a gas source 95 a pipe 96 and a conduit in the part 97 and a conduit in the part 97 to the Inside the cathode 98 passed. A hollow cylindrical anode 99 is spaced apart by and arranged coaxially with the cathode 98. A power source 100 with a voltage of about 150 V is between the cathode 98 and the anode 99 by means of lines 101 and 102 switched. A magnetic, axial collimator field is used in the in F i G. 4 is obtained by means of coils not shown, and the direction of the magnetic field is indicated by the arrow H. Between the cathode 98 and the anode 99 an arc is maintained. The electron source in F i G. 4 generates an electron beam 103 of about 3 A at an accelerating potential of 2.5 kV. The acceleration of the electrons from the electron source is due to an accelerating electrode (not shown) can be obtained in a similar manner as it was described in connection with FIG. 1.

In the in F i g. 4, a hollow cylindrical tungsten cathode 109 is fastened in an annular end plate 105. A hollow cylindrical carbon anode 110 is arranged within an annular part 108. The part 108 has flanges at both ends. The flange portion at one end of portion 108 is held in place by insulation 106, which in turn is supported by end plate 105. An annular shield 107 is attached to the part 106 inside. The shield 107 closely encloses the cathode 109. The flange at the other end of part 108 is connected to an annular end plate 113. The plate 113 has an annular tungsten insert 114. An annular electrode 115 is arranged directly next to the end plate 113. An acceleration electrode 116 is provided on the other side of the electrode 115 and held at zero potential. Gas from the gas source 19 is fed into the interior of the anode 110 through a tube 112.

To close the opening in the plate 105 when the electron source is not needed, a shutter 104 is provided. The electron source and the ion source of the arrangement as shown in FIG. 4 are shown in a suitable housing included. If the device according to this figure in a Spacecraft is used, the outlet duct of the housing communicates with areas in which the negligible atmospheric pressure of space prevails, so that the housing is evacuated in this way to the pressure prevailing in the external space will. If the in F i g. 4 is used for other purposes the housing cannot pressurize about 3 - 10-s mm Hg by means of a pressure pumps shown in the same way as in connection with the F i g.1 must be evacuated. Electrodes 98, 99, 109 and 110 are on a common axis arranged one behind the other, and this axis is parallel to the direction of the magnetic field H. An arc discharge 111 is generated in the ion source ignited in the same way as was described in connection with FIG. The electron beam 103 is directed at this arc discharge 111, so that essentially a complete space charge neutralization at all points inside and beyond the ion source takes place in order in this way a space charge-neutralized Create beam 117 from electrons and ions in the same way as it is related with the Fig. 1 was described.

The magnitude of the thrust caused by one shown in FIG. 4 shown device is obtained is directly dependent on the type of atoms which are in the interior of the Anode 110 are introduced for ionization. In the elimination of the space charge effect by neutralization in the entire propulsion system, ions of different masses and energies are used to create a drive motor with different in this way to create defined shear effects. On the other hand, the optimal thrust is under achieved various conditions. With conventional ion sources, the choice is the The type of ion causing thrust is limited and closely related to the special conditions of space charge tied together. Since it is possible to have a larger range of fuel in the in Fig. 4 can be used by taking along the device the fuel-related problem can be reduced since it is possible to use as fuel To use material that is collected in space.

An advantage of using certain elements of greater atomic weight in the in F i g. 4 shown device, such. B. Ti, U etc. (these are at Room temperatures condensable) is that by "pumping" as a result of the getter effect these fuel ions can be represented in a high vacuum test facility. Such systems are first pumped out by vacuum pumps. By injecting one determined these fuel ions in the test facility by means of a device shown in FIG. 4 shown Device, the system is pumped out further by the getter effect of these ions, when they condense at room temperatures. In this way it is possible to do this Basic phenomena associated with ion propulsion in space, in the laboratory to study in depth.

In addition to the use of ion plasma for direct propulsion, the plasma also used to separate one. Heat neutral gas and ejecting the heated gas stream through a nozzle to provide a thrust effect obtain. Such a system is shown in FIG. 5 shown. This device can can be used for a machine in a lower specific thrust range.

The in F i g. 5 essentially corresponds to the device shown the device of FIG. 4. Only next to the end plate 113 is in place of the Electrode a nozzle 118 is provided.

A magnetic field with an average flux density of about 6000 Gauss is generated generated by coils not shown. The direction of this field is through the Arrow H indicated and runs parallel to the axis of the cathode 109 and the anode 110. The in F i g. The device shown in FIG. 5 is enclosed in a suitable housing, and the housing communicates with the cosmic space in which the atmospheric pressure is negligible is when the device is used to propel spacecraft. That Propellant gas introduced into the anode is heated by the arc discharge 111, and the heated gas 119 is expelled from the device through the nozzle 118.

Claims (7)

Claims: 1. Device for generating a space charge neutralized Beam of charged particles with an ion source and a source of high energy Electrons arranged next to each other on a common symmetry and beam axis are, characterized in that the electron beam in the direction of the ion beam directed through the ion source and the ion extraction electrode and that a common magnetic guiding field for the ion and electron source is provided whose lines of force are parallel to the common beam and symmetry axis are directed. 2. Apparatus according to claim 1, characterized in that the Ion source consisting of a hollow cylindrical anode and one arranged coaxially to this there is a hollow cylindrical cathode, both of which are open at their end faces, and an ion acceleration electrode opposite the opening of the anode facing away from the discharge space it is arranged that the electron source is opposite to that facing away from the discharge space Opening of the cathode is arranged, and a surrounded by an electrical shield, is known electron source with two-electrode system with plasma cathode, and that between the shield and the ion source an electron accelerator is arranged. 3. Apparatus according to claim 1 or 2, characterized by a Device, seen in the direction of the beam, beyond the ion acceleration electrode and which further accelerates the ions and the energetic electrons delayed. 4. Device according to one or more of the claims 1 to 3, characterized in that the electron accelerator between the electron source and the chamber accelerate the electrons gradually causes. 5. Device according to one or more of claims 1 to 4, characterized characterized in that the electron accelerator means from the electrons the electron source is accelerated to a final energy of about 100 keV and that the Accelerators for the ions bring them to a final energy of about 100 accelerate keV. 6. Apparatus according to claim 4, characterized in that the Acceleration stages for the electrons are designed in such a way that they move the electrons accelerate from the electron source to about 600 keV and that the accelerator accelerate the ions to about 600 keV. 7. Device according to one or several of claims 1 to 6, characterized in that it is used as a drive for a spaceship is used. Publications considered: German Patent No. 661337; U.S. Patent No. 2,927,232; M. v. A r d e n n e , Tables @ of electron physics, ion physics and super microscopy, Volume I, 1956, Berlin, P.131.