DE1188221B - Process for generating an energy-rich, high-temperature gas discharge - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

G 21

German class: 21g-21/21

Number: 1188221

File number: U 6349 VIII c / 21 g

Filing date: July 15, 1959

Opening day: March 4, 1965

The invention relates to a method for generating a high-energy, high-temperature gas discharge between a water-cooled, cup-shaped cathode charged with gas and a water-cooled, hollow, optionally cup-shaped anode, these electrodes being spaced from one another and with their axes in alignment in one of an outer chamber Surrounded evacuated chamber and within an intense magnetic guide field, which is directed in the axial direction of these electrodes, are arranged and these electrodes are subjected to an ignition voltage and a working voltage. High energy or high temperature arc discharges are used as a dissociation mechanism in plasma devices. The known type of arc discharges cannot operate in the presence of high magnetic fields and at pressures low enough for the dissociation mechanism to be effective. For example, it is not possible with known arcs, with currents of at least 100 A between a cathode and an anode at a distance of at least 30 cm from this cathode and in the presence of a strong magnetic field (6000 Gauss) and in a vacuum of 3 × 10 ~ ⁵ mm Hg to work. The discharge simply cannot be started if these values are set, since the gas ionization in the arc is insufficient. The object of the invention is to provide procedural measures in order to generate a high-temperature arc discharge with the stated operating parameters.

This object is achieved according to the invention in that the outer chamber and that of this enclosed arc discharge chamber are evacuated separately to different pressures that Gas feed rate to the interior of the cathode, starting from one for igniting the gas discharge required feed speed, reduced and at the same time the working voltage of the arc is increased so much and the pressure in the chamber is reduced so much that the arc discharge is drawn into the interior of the cathode from the front surface of the cathode.

According to the invention, for igniting the arc discharge between a hollow cathode and an anode or between a hollow cathode pair and a hollow anode arranged between these two hollow cathodes, a predetermined gas feed rate to the interior of the hollow cathode or the hollow cathode pair is first maintained and then (after the ignition of the method for Generate an energetic
high temperature gas discharge

Applicant:

United States Atomic Energy Commission,

Germantown, Md. (V. St. A.)

Representative:

Dr.-Ing. W. Abitz, patent attorney,

Munich 27, Pienzenauer Str. 28

Named as inventor:

John Sidney Luce, Oak Ridge, Tenn. (V. St. A.)

Claimed priority:

V. St. ν. America of July 15, 1958 (748771) -

Arc discharge) the gas feed rate to the hollow cathode or to the hollow cathode pair is reduced so that the arc discharge is drawn from the front surface of the cathode (s) into the interior thereof will. Only when the discharge ends in the cathode itself will there be complete ionization of the feed gas and maintain the arc discharge even if the pressure in the Discharge space reduced to a very small value in the presence of a very strong magnetic field will. The previously known procedural measures for generating high-energy arc discharges are not designed to solve the problems outlined above. The task of a high-energy arc by dissociating a substantial percentage of molecular ions passing through the arc in the manner described in US Pat. No. 3,030,543 could only be carried out through the invention proposal be solved.

There are already ion sources with cup-shaped hollow cathodes and ion sources with magnetic ones Leading fields (Pig Ion Source) known. These known ion sources are intended to increase the ion yield to make it as big as possible. The gas supply speed is regulated accordingly. According to the proposal of the invention, however, the gas supply speed is reduced to the arc discharge to draw from the front surface of the cathode or cathodes into the interior thereof,

509 517/332

which is clearly not the case with the known ion sources.

The invention is explained in more detail, for example, using the figures.

F i g. Fig. 1 shows a sectional view of a suitable for carrying out the method according to the invention Contraption;

F i g. 2 shows a sectional view of a hollow cathode with the electron paths running therein;

F i g. 3 shows a sectional view of another embodiment a device for performing the method according to the invention;

F i g. 4 shows a sectional view of a further embodiment of a device suitable for this.

The bows described below are made under fairly high tension and with a fairly operated with a strong current, so that the heating of the electrodes is a problem. This problem was made through the use of electrodes made of tungsten or some other conductive material solved, which has a high melting point and at the same time is a good conductor of heat. For the Carbon can be used for anodes, but this does not appear to be practical, since carbon is used at high Temperature is a poor conductor of heat, so that with a partial evaporation of the anode material must be reckoned with what is undesirable. The electrodes are in thick water-cooled copper sheaths firmly fitted.

At a pressure for example of 3 x 10 ~ ⁵ mm Hg or lower the sheet in the apparatus in F i g. 1 a hollow cylinder, the arc flow in this cylinder being guided close to the inner cathode wall. The arc current depends on the emission across the magnetic field within the hollow cathode. There is no reduction in emission when the arc is in a strong magnetic field of e.g. B. 6000 Gauss is operated. The sheets in the devices according to FIGS. 3 and 4 are not hollow, but their current strength also depends on the emission across the magnetic field within the hollow cathode.

The deuterium arcs described here have at least two novel features that allow they are different from other arches and operate under both low and high pressure Enable energy. The first characteristic consists in the cross-field emission caused by the use of a large surface area from which electrons can enter the system is achieved. The deuterium gas that the interior of the hollow Cathode is fed is completely ionized before it leaves the hollow cathode. Because inside the cathode If adequate space charge neutralization takes place, it is possible to reduce the pressure without to impair the emission properties of the sheets. The second essential feature is in that See the existence of an axial stress gradient in the arch. The electrons are from the Inner wall of the cathode accelerated from radially. Some of those electrons that collide before they return to the wall are trapped near the inner cathode wall and then pulled out of the cathode as a result of this axial voltage gradient.

In the device according to FIG. 1 is a hollow, elongated, cup-shaped cathode 1 in one.

Block 3 and a hollow, elongated, cup-shaped anode 2 are arranged in a block 4. Cathode shields 5 and 6 are supported by insulators 8 and 9 attached to an outer chamber wall 13. The chamber wall 13 also carries an anode shield 7 by means of an insulator 10. Magnets 11 and 12 generate a strong magnetic field of, for example, 6000 Gauss, the direction of which is indicated by the arrow H. Deuterium or tritium gas is fed from a gas storage container 14 via a pipe 15 to the interior of the hollow cathode 1. The cathode and anode are cooled by a coolant flowing through pipes 33.

By the walls 13 an outer vacuum chamber 21 is limited, which by a pipe piece 23 with connected to a vacuum pump. An inner vacuum chamber 20 is delimited by walls 17 and connected by a piece of pipe 22 to a vacuum pump. Guide walls are adjacent to the cathode 1 18 and adjacent to the anode 2 guide walls 19 are provided. The guide walls 18 and 19 are insulated stored. An arc ignition auxiliary device, for example a high-frequency voltage source 31, which has a Welding transformer of the usual type is connected at one end to the anode via a line 32 2 and at its other end via a line 30, a switch 29 and a line 28 to the Cathode 1 connected. A DC voltage source, for example a multi-cell battery 25 with variable Tap, supplies the operating voltage for the anode-cathode line. The battery 25 is while on its one side via a line 24 to the cathode 1 and on its other side via a Switch 26 and a line 27 connected to the anode 2.

The blocks 3 and 4 are mounted so as to be insulated from the chamber wall 13. In the case of the FIG. 1 shown Device is z. B. the length of the cathode 12.7 mm, its outer diameter 19.05 mm and its inner diameter 9.525 mm. The anode has a length of 12.7 mm, an outer diameter of 19.05 mm and an inner diameter of 12.7 mm.

In the case of the FIG. 1, when starting up, gas is supplied from the supply source 14 to the cathode 1 via the pipe 15 until the pressure in the cathode and in the chamber 20 reaches a value of about 3 · 10 ^-3 mm Hg, whereupon the high-frequency voltage source 31 is connected to the Electrodes 1 and 2 is placed. Furthermore, a DC voltage source 25 is applied to the electrodes. The arc is ignited on surfaces 34 and 35 of the cathode and anode. After the arc 16 has been ignited, the high-frequency source is switched off and the gas supply is reduced until the arc moves from the surfaces 34 and 35 of the electrodes into the interior of the electrodes. The gas feed rate is kept at a value which is just sufficient to achieve complete space charge neutralization within the hollow cathode, while the pressure in the chamber 20 is steadily reduced to about 3 · 10 ~ ^r> mm Hg or lower. The pressure in the outer chamber 21 is kept at a value of about 10 ~ ⁴ mm Hg. During operation, the pressure difference between the two chambers is kept at a constant value.

During the entire operating time, a magnetic field with a strength of about 6000 Gauss is maintained by the magnets 11 and 12 in the device referred to. As the pressure in chamber 20 is reduced, the voltage across the electrodes increases; when the pressure in the chamber 20 has reached a normal operating level of, for example, 3 x 10 ^-3 mm Hg, the voltage between electrodes 1 and 2 is about 400 volts and the arc current is then about 100 A.

So that the arc out of the interior of the cathode under the conditions specified above can be operated, it is necessary that the gas flow be maintained at one speed which is sufficiently low to allow adequate space charge neutralization within the Cathode, but not in the main volume; In addition, the bore of the cathode must be more precise Alignment with the magnetic field.

F i g. 2 shows an example of the electron paths within the cathode. As mentioned, the Electrons accelerated radially from the inner wall of the cathode. Some of those electrons that, before they return to the wall, collide, are captured and out of the cathode pulled out due to the axial stress gradient in the arc so that they move towards the anode. Further collisions along the length of the arc take place on their way to the anode. Everyone These collisions with gas molecules result in the formation of ions, so that the arc is formed and is entertained. These ions become the cathode along the magnetic field as a result of the Accelerated stress gradients in the arch. Since the movement of the ions is not random or random, but these are quickly led to the cathode, losses are due to diffusion and recombination greatly reduced. In order to take advantage of this advantage, the guide walls 18 and 19 are between the electrodes and the working volume of the bow. A large number of ions leading to the cathode are accelerated and recombine, are then prevented from entering the as neutral particles Chambers 20 and 21 flow back.

It can bend with other gases, such. B. air, hydrogen, argon, nitrogen and helium operated will; for the study of thermonuclear processes, however, is the use of deuterium or tritium is essential.

The anode does not necessarily have to be cup-shaped; it can also be made massive be. The heating of the anode and thus the scattering of impurities can result from the use a rotating anode that allows electron bombardment over a large surface area distributed should be reduced to a minimum.

The bow described above is an effective dissociation device. This arc has been found to have a splitting efficiency of up to 25 ^fl / o when used to dissociate 20 keV deuterium molecular ions.

In the device according to FIG. 3, a first hollow, cup-shaped tungsten cathode 40 is provided, which is arranged in a copper block 42. The copper block 42 is enclosed by a housing 44 which is mounted in an insulated manner in the outer chamber wall 62. A second hollow, cup-shaped tungsten cathode 41 is arranged in a copper block 43. The copper block 43 is enclosed by a housing 45 which is mounted in an insulated manner in the outer chamber wall 42. Cathode shields 46, 47 and 48 provided with an opening and an electron reflector 49 provided with an opening are mounted in an insulated manner in the inner chamber wall 54 and are arranged adjacent to the first cathode 40. Corresponding cathode shields 51, 52 and 53 and an electron reflector 50 provided with an opening are mounted in an insulated manner in the inner chamber wall 54 and are arranged adjacent to the second cathode 41. These cathode shields and electron reflectors act as guide walls between an inner vacuum chamber 80 and an outer vacuum chamber 81. The inner chamber wall 54 carries a hollow, elongated anode 78.

Magnets 60 and 61 generate a strong magnetic field, the direction of which is indicated by the arrow H. Deuterium or tritium gas is supplied from a supply source 58 to the interior of the hollow cathode 40 via a pipe 56. Furthermore, deuterium or tritium gas is supplied from a supply source 59 via a pipe 57 to the interior of the hollow cathode 41 .

The inner vacuum chamber 80 is formed by walls 54 and connected to a vacuum pump by a pipe 55. The outer vacuum chamber 81 is formed by walls 62 and connected to a vacuum pump by a pipe 63. An auxiliary arc ignition device, for example a high-frequency voltage source 74, which can be a welding transformer of the usual type, is a switch on one side via lines 71 and 73 and via lines 71 and 72 to cathodes 40 and 41 and on the other side via a line 75 76 and a line 77 connected to the anode 78. An operating voltage source, for example a multi-cell battery 67 with a variable tap, is connected with one side via lines 64 and 66 and lines 64 and 65 to the cathodes 40 and 41 and with its other side via a line 68, a switch 69 and a line 70 connected to the anode 78.

In the case of the FIG. 3 device shown have z. B. the cathodes 40 and 41 have a length of 12.7 mm and an inner diameter of 15.88 mm. The hollow anode 78 then has a length of 20.32 mm and an inner diameter of 5.08 mm. For long arches up to 1.83 m in length, anodes with a diameter of up to 15.24 mm can be used. The length of the anode is not critical for operation. The anode is generally made long in relation to its diameter so that a lower pressure can be achieved in the central region than at the cathodes.

During start-up, gas is supplied from the supply source 58 via the pipeline 56 to the cathode 40 and from the supply source 59 via the pipeline 57 to the cathode 41 until the pressure in the hollow cathodes and in the chamber 80 reaches a value of about 3 × 10 ^-3 mm Hg reached, whereupon the HF voltage source 74 is applied to the cathodes 40/41 and the anode 78 by closing the switch 76. Furthermore, the DC voltage source 67 is applied to the cathodes 40/41 and the anode 78 by closing the switch 69. The bow is attached to the catholic

the surfaces 82 and 83 ignited. After the arc 79 has been ignited, the high-frequency source 74 is switched off by the switch 76 and the gas supply is reduced until the arc moves from the cathode surfaces 82 and 83 into the interior of the cathodes. The gas supply to the arc is maintained at a rate sufficient to bring about a full space charge neutralization within the hollow cathode, while the pressure is reduced continuously in the chamber 80 until it reaches a value of about 3 x 10 ^-5 mmHg or lower. The pressure in the outer chamber 81 is maintained at a value of about 3 · 10 ^-4 mm Hg. The pressure difference between the two chambers is kept at a constant value under normal operating conditions.

During the entire operating time is in the designated device by the magnets 60 and 61 maintain a magnetic field of about 3000 to 6000 Gauss. The one with the device after F i g. The arc produced in FIG. 3 has a much higher resistance than that with the device according to FIG. 1 generated and was operated with voltages up to 1 kilovolt and with arc currents up to 100 A.

So that the arc under the conditions described above from the interior of the cathode can be operated out, must, as in the device of FIG. 1, the gas flow be maintained at a rate sufficiently slow to allow adequate space charge neutralization takes place within the cathodes but not in the main volume; also have to the bores of the cathodes are in exact alignment.

In the device according to FIG. 3 plays the problem the heating does not play such an important role as in the device according to FIG. 1. The type of discharge at the device according to FIG. 3 is such that the electrons in the discharge oscillate between the cathodes, until they suffer a collision and gradually become different with a precession motion Parts of the inner surface of the hollow anode arrive. For the devices according to FIGS. 3 and 4 cooling tubes are also required, which in the FIG. 1 be arranged in the manner shown can. The cooling tubes are shown in FIGS. 3 and 4 are not shown for the sake of clarity. the Tungsten cathodes 40 and 41 are tightly fitted in the blocks 42 and 43, so that a good heat transfer takes place during heating.

In the device according to FIG. 3 provided cathode shields and electron reflectors serve the same purpose as the guide walls of the device according to FIG. 1. In the device according to F i g. 3, one of the cathodes can optionally be replaced by a plate.

The in the device according to F i g. 3 generated arc discharge does not necessarily have to be in a straight line Line can be hidden, but can with an appropriate design of the magnetic field and the electrodes be curved. For example, a device as shown in FIG. 4 is shown a toroidal shape curved arc 98. The anode is essentially a toroid with a segment removed from it is to insert a curved hollow cathode and the apertured shields and to enable electron reflectors. In such an arrangement a Emission takes place at both ends of the cathode. In the mode of operation are those shown in FIGS. 3 and 4 shown Devices similar to each other.

In the device according to FIG. 4 is a curved hollow tungsten cathode 85 in a copper jacket 104 firmly inserted. On the outer chamber wall96 is a circularly curved hollow anode 86 attached by means not shown. The ends of the anode 86 lie on the end surfaces 116 and 117 opposite the hollow cathode. An opening is provided through the inner chamber wall 93 Cathode shields 88 and 89 and an electron reflector 87 provided with an opening stored in an isolated manner and arranged adjacent to the cathode surface 117. Adjacent to the cathode surface 116 are also cathode shields 90 and 91 provided with an opening and one with an opening provided electron reflector 92 is arranged, which isolates from the inner chamber wall 93 be worn.

A strong magnetic field, for example of 3000 to 6000 Gauss, is generated by magnetic coils 103. Magnetic coils 103 are arranged around the hollow anode 86 over its entire length. The direction of the magnetic field is indicated by the arrow H.

Deuterium or tritium gas is transferred from a supply source 100 via a pipe 99 to the interior of the central part of the hollow cathode. The feed pipe 99 is surrounded by a pipe section 105. An inner vacuum chamber 102 is delimited by the wall 93, which is above the pipe section 95, which is connected to the chamber wall 93, is connected to a vacuum pump. the Wall 96 delimits an outer vacuum chamber 101, which via a tubular extension piece 97 with connected to a vacuum pump. An auxiliary arc ignition device 112 (RF voltage source), for example a welding transformer of the usual type is with one side connected to the cathode 85 via a line 111 and with its other side via a line 113, a switch 114 and a line 115 connected to the anode 86. An operating DC voltage source 107, for example a multi-cell battery with variable tap, one side is connected to the cathode via a line 106 85 and with its other side via a line 108, a switch 109 and a line 110 with the Anode 86 connected.

The electron reflectors 87 and 92 and the cathode shields 88, 89 and 90, 91 act as baffles to create a differential pumping action between the inner and outer chambers in a similar manner Way as in the device according to F i g. 1 to achieve.

The mode of operation of the device according to FIG. 4 corresponds to that of the device according to FIG. 3.

The arc discharges in the devices according to FIGS. 3 and 4 can be used to generate a Source of energetic ions and electrons and for dissociation and / or ionization of molecular ions be used. Furthermore, some of the discharge can be constricted by magnetic mirror coils and compressed, whereby an energy multiplication is achieved, which is particularly useful for studies thermonuclear processes is important.

An advantage of the devices according to FIGS. 3 and 4 is that pinch discharges induce

can be adorned without the strong pinch current in concentrated areas of the electrodes applied. In fact, it takes place at some point during the pinch operation on the device according to FIG. 4 there is no loading of the cathodes at all by the discharge. Through this the heating as well as the erosion of the electrodes and the entry of foreign substances into the discharge considerably reduced.

Claims (5)

Patent claims: 1. Process for generating a high-energy, high-temperature gas discharge between a water-cooled, cup-shaped, gas-filled cathode and a water-cooled, hollow, possibly cup-shaped anode, with these electrodes at a distance from one another and evacuated with their axes in alignment in an outer chamber surrounded Chamber and within an intensive magnetic guidance field that runs in the axial direction these electrodes are directed, arranged and these electrodes with an ignition voltage and applied with a working voltage, characterized in that the outer chamber and the arc discharge chamber enclosed by this separately on different Pressures to be evacuated, the gas supply rate to the interior of the cathode, starting from a feed rate required to ignite the gas discharge, decreased and at the same time the working tension of the bow increased as well as the Pressure in the chambers is reduced so much that the arc discharge from the front surface the cathode is drawn into the interior of the cathode. 2. The method according to claim 1, characterized in that mm to maintain a continuous arc discharge of about 100 A, the reduced pressure in the discharge chamber about 3 x 1O ^-5 mm Hg and the reduced pressure in the outer chamber about 3 · 10 ^-4 Hg is, the working voltage is adjusted to about 400 V DC and the magnetic field to a field strength of about 6000 Gauss and that the gas supplied is deuterium. 3. The method according to claim 1 or 2, characterized in that in an arrangement according to. F i g. 3 with a second cup-shaped, water-cooled and gas-charged cathode die Gas feed rate to the two cathodes is changed simultaneously, so that the Discharge is drawn into the interior of the two cathodes. 4. The method according to claim 1 or 2, characterized characterized in that in an arrangement according to F i g. 4 with partially annular and tubular Anode and cathode the gas is fed to the cathode cavity at the longitudinal center of the cathode. Considered publications: German patent specifications No. 735105, 736130,
861299, 873 594, 879 583; Austrian Patent No. 132189; French Patent No. 883,711; British Patent Nos. 400 320, 706 036; U.S. Patent No. 2,510,448; "Annalen der Physik", 5th part, Vol. 36, 1939, pp. 9 to 37; "The Review of Scientific Instruments", Vol. 24, No. 5, May 1953, pp. 394/395. 1 sheet of drawings 509 517/332 2. 65 © Bundesdruckerei Berlin