US2217187A

US2217187A - Electrical discharge apparatus

Info

Publication number: US2217187A
Application number: US61881A
Authority: US
Inventors: Charles G Smith
Original assignee: Raytheon Manufacturing Co
Current assignee: Raytheon Co
Priority date: 1936-02-01
Filing date: 1936-02-01
Publication date: 1940-10-08
Anticipated expiration: 1957-10-08

Description

- 8. 9 c. s. SMITH ELECTRICAL DISCHARGE APPARATUS ori inal Filed Feb. 19:56 2 Sheets-Sheet 1 TTOQA/L'Y Oct. 8, 1940- c. G. SMITH ELECTRICAL DISCHARGE APPARATUS iori inal Filed Feb. ,1, 1936 2 SheetsSheat 2 Patented Oct. 8, 1940 PATENT OFFICE ELECTRICAL DISCHARGE APPARATUS Charles G. Smith, Medford, Mass, assignor to Raytheon Manufacturing Company, Newton, Mass., a corporation of Delaware Application February 1, 1936, Serial No. 61,881 Renewed January 10, 1939 22 Claims.

My invention relates to electrical discharge apparatus, and more especially to gaseous conduction apparatus. More particularly, my invention relates to apparatus in which a discharge through gas or vapor is accompanied by the uneven distribution of gas or vapor throughout the apparatus, thus creating a greater pressure in one portion of the device than exists in another portion.

In prior applications, Serial Nos. 13,145, now Patent No. 2,137,198, and 13,146, filed March 5, 1925, I have disclosed two types of apparatus for creating a difference in pressure by virtue of a discharge through a vapor. In one type the pressure is built up by electrostatic means, and is due to a drop in potential along the entrance leading to the inside of a hollow cathode. charged gas particles coming within the influence of this field are drawn into the hollow cathode, and thus the pressure is built up. In the other type, the means for creating the pressure is the magnetic field interacting with the ionized gas particles. The field and current carrying gas particles are at an angle to each other which results in giving to the gas particles a motion which causes the gas to be rotated within a hollow cathode. This whirling motion throws the gas particles toward the outer portions of the inner space of the cathode, leaving the. central portion more or less vacuous, and thus causing gas from the remainder of the apparatus to rush in. In the present device, I obtain a pressure in the cathode region by a combination of magnetic and electrostatic means.

Referring to the drawings,

Fig. l is a sectional view of a discharge device embodying the invention with the circuits thereof shown diagrammatically;

Fig. 2 is a diagrammatic showing of the course of an electron from the cathode to the anode;

Fig. 3 is a view similar to Fig. 1 of anotherembodiment of my invention;

Fig. 4 is a view also similar to Fig. 1 of an additional embodiment of my invention.

Referring to Fig. l, the device is composed of two cylindrical metal members of non-magnetic material, such as copper, welded or otherwise joined to form a tubular casing or envelope I, the interior center portion l6 of which constitutes the cathode surface adapted to emit electrons. Each of these members supports an annular or circular magnetic pole piece comprising a cylindrical portion 2 and an inward ring portion 2| forming a restricted opening or gap 19 between their inner ends. These magnetic pole pieces may be sup- Positively ported by having the casing member spun over both

edges

30 and 3| of the cylindrical portion 2 of the pole pieces. The space within the device is thus divided into an outer enclosed annular cathode space M lying in front of the cathode surface 16, and an interior space lying within the pole pieces, and segregated from the cathode space by gap I9.

The lower end of the container or casing is closed and is provided with a reentrant sealed-in glass press 8 insulatingly supporting two main anodes 5 and an auxiliary anode 6 spaced from the cathode I6. The auxiliary anode is adapted to cooperate with the cathode 16 to maintain an auxiliary discharge in the normal operation of the device. The auxiliary anode 6 is in the form of a disk which is substantially concentric with the circular ends of the pole pieces and is of such a diameter that the peripheral portion lies between the opposite ends of the pole pieces. These magnetic pole pieces form enclosure means constituting a chamber enclosing the space in front of the cathode-emitting surface 16, separating said space from the anode space and restricting the discharge between the auxiliary anode and the cathode to a confined region, in-- cluding the restricted opening or gap 19. The distance between the peripheral portion of the auxiliary anode and pole pieces is such that with the vapor or gas used, gap I9 is practically insulating. To insure the absence of any discharge on the lead wire of auxiliary anode 6, an insulator I of any suitable material, as lava, is disposed around the wire. The upper end of the casing is also closed, and is provided with a reentrant sealed-in glass press 22 insulatingly supporting a filamentary cathode IS in the annular region 14 for initiating the discharge through the tube. The device is exhausted or evacuated in the usual manner, and has a gas filling. Capsule l8 contains the necessary chemicals for the liberation of a free metal, preferably an alkali metal like caesium. In operating the tube with caesium, it is desirable that the coolest portion of the device be not hotter than about 75 C. A gas, preferably of the rare group, may be used in conjunction with the alkali metal. Other vapors or gases, such as mercury vapor, may also be used.

A permanent magnet 4 induces a magnetic fleld through the pole pieces that crosses the annular gap 19. The lines of force of the magnetic field are substantially perpendicular or transverse to the normal electron paths from the cathodes l5 and Hi to the anode 6. The pole pieces concentrate these lines of force into the narrow annular region between said cathodes and the anode 6 provided by the gap I9.; Coil 3 induces additional magnetic flux through the gap. It is possible to dispense with either the coil or the permanent magnet by making one or the other strong enough so that both are not necessary. The two main anodes 5 are disposed outside the chamber formed around the cathode I6 and near two apertures I 0 in portion 2I of one of the pole pieces to maintaln a discharge with the space enclosed around the cathode. The interior openings of each of the pole pieces 2| are enclosed by two grids 9 made of some metallic mesh like nickel or non-magnetic steel. The cathode filament I 5 is energized by portion 40 of the secondary of transformer 20, the portion 42 of the secondary of transformer 20 applying a difference in potential between filament I5 and'the casing to easily initiate a discharge. The secondary winding of transformer II, which supplies current to be rectified, has its outer terminals connected through

leads

24 and 23 to the main anodes 5, and its center tap 25 leads' through coil 3 to load I2, which has its other terminal grounded on casing I by conductor 26.

The operation of the tube is as follows. A battery of about 200 volts is connected between the auxiliary anode 6 as the positive terminal and the casing I as the cathode by wires 26 and 21 through regulating resistance I3. Cathode I5 energized as shown'emits electrons which under the action of transformer winding 42 maintain a gaseous discharge between the filamentl5 and cathode surface I6, producing electrons and ionizing the gas. This initiates a flowof electrons from cathode surface I6 to the auxiliary anode 6, but these electrons will. not take a direct path through the enclosure region I4 tothe auxiliary anode, but will be compelled totake a more or less curvilinear and tortuous path by virtue of the magnetic field of permanent magnet 4, which is most intense at air gap I9 adjacent the periphery of the auxiliary anode, and has also some lines of force that permeate the entire annular region I4. The interaction of the magnetic field and the face I6 and anode 6 imparts to the electrons Y traveling from cathode surface I6 to the auxil- 'such particles an electron is liable to collide with in the course of its fall through the potential drop between the cathode surface I6 and the auxiliary anode.

Once the discharge between the cathode surface I6 and the auxiliary anode has been initiated, the filament I5, if desired, may be rendered inoperative by cutting off the supply of current.

The discharge will come from cathode sur-- face I6 of the casing rather than from the pole pieces. The gaps I9 between the periphery of auxiliary anode 6 and the circular edges of the pole pieces are so small as to be insulating, due to the lack of a sufficient number of gas particles between the opposing surfaces to be ionized. This principle is well known and is set forth in greater detailin my prior Patents Nos. 1,617,171 to 1,617,177, inclusive. Electrons, although very easy to be drawn into a conducting material, are withdrawn; therefrom only with great difiiculty. Thus, while active cathode surface I6 of the casing is substantially at the same potential as the pole pieces with respect to anode 6, practically all the electrons going to anode 6 will be withdrawn from the cathode surface I6.

Any electrons which go from the pole pieces to the auxiliary anode would carry very little of the current due to their small number.

Electrons drawn from cathode surface I6 of easing I have such a long path in falling through the drop of potential that there are considerable collisions with gas particles, and hence considerable ionization of the gaseous medium is effected Ions thus created near the cathode surface I6 of the casing arepositively charged,'and would naturally attract electrons from the cathode proper. Thus more and more electrons would be pulled out from the cathode. In actual use, caesium vapor settles on surface I6 and promotes emission, though the interior of I6 could be coated with a suitable material, such as oxides or the alkaline earth metals, as strontium or barium, or any of the other well-known materials for reducing the work function of the cathode. Thus electron emission occurs from cathode surface I6 of the casing although it is farthest away from the auxiliary anode because electrons coming from there cause maximum ionization of the gaseous medium, and cause maximum conduction of electricity.

Referring to Fig. 2, an electron path is shown diagrammatically. Outer ring I6 represents thecathode surface while inner circular section 6 represents the auxiliary anode. The electron is drawn out from cathode I6 and normally would go in a direct line to auxiliary anode 6. The magnetic field, however, constrains it to move in a course having circular component with the magnetic lines of force as an axis. By suitably energizing coil 3, the magnetic field, due to the permanent magnet, is greatly augmented, and the ionization 'in the cathode enclosure I4 and gap I9 is greatly increased because of the very much longer electronic paths. If an electron starts from the cathode surface in a magnetic field and assuming that no gas particles are met with, it will describe an approximately cycloidal curve and be curled back into the cathode surface at the same distance from the anode. Another electron may be withdrawn from the cathode surface, and may strike a gas particle at 4| and ionize it.

The greatest velocity of the electron is at the point of the curve nearest to the auxiliary anode 6, and any collisions at that point will be ionizing if the speed is great enough. From this point II, the electron will start again on a curvilinear path, and thus will gradually work its way toward auxiliary anode 6. As the field grows in intensity upon approaching the auxiliary anode, the curvilinear paths of the electron with reference to the lines of force will become sharper. The more intense the field is, the greateris the curling force on the electrons, and the greater is the potential necessary to finally pull the electron through to anode 6. The

varying intensity of the field thus has the .effect of varying the potential gradient between the cathode surface'lfi and the anode 6. The magnetic field distorts the normal potential distribution between the cathode and the auxiliary anode 6 and the drop of potential or gradient willbe the steepest or highest right at anode region IS in the direction between the cathode and the auxiliary anode 6 because the field is most intense. This results in having a comparatively great anode potential drop. Electrons in that region will, therefore, travel in very sharply curvilinear paths and for considerable distances around the anode compared to the actual direct distance to the-anode. Thus the magnetic field acts on the discharge through the gap l9 to impart to the electrons movement over relatively extended or lengthened paths, impeding their flow towardthe auxiliary anode 6 and limiting the current to the auxiliary anode to a low value while maintaining a high voltage gradient in said gap.

The device has thus opposing cathode and anode surfaces with a means surrounding them for altering the potential gradient between the cathode and anode in an annular region between the two electrode surfaces. Furthermore, this means, which is coil 3 in this instance, comprises the pole pieces as members between the cathode-anode surface.

In the ordinary gaseous discharge, electrons carry the greatest portion of the current on account of their tremendous speed. Because of their relatively slow speed, positively charged ions carry only a small portion of current in spite of the fact that each ion carries a charge which is equal to or greater than the charge on an electron, though opposite in sign. In the discharge space M, electrons though travelling fast are caused to take a path which is so much longer than the direct path that their speed avails them little. The result is that ions carry a much greater portion of the current than ordinarily is the case. The electrons may thus be considered to be more or less idle, as far as carrying current is concerned, but more than make up by the creation of an enormous number of ions.

The increase in the length of the path with increase in the intensity of the field results in an intense ionization in region IS. The large number of ions created are repelled by auxiliary anode 6, and are urged in toward region I l adjacent the cathode. Since the potential gradient is steepest in gap Id, ions will be repelled with the greatest force in that regionand violently thrown into region l4. These ions are created from neutral gas molecules, and the constant tendency of ions to rush into region l4 toward the cathode results in gas particles being sucked in toward the periphery of the auxiliary anode, there to be ionized and repelled toward the ca'thode. This is the pumping efiect by electrostatic force, and results in the building up of a pressure in the cathode region.

The pumping effect may be considered from a difi'erent angle. The electrons travelling in a generally circular direction may be considered as a circular current of electricity. The reaction between this circular current and the magnetic field results in a radial force which is exerted on the current-carrying medium, the gas or vapor. On the other hand, the general radial current component represented by ions interacts with the magnetic field to give the other current component, consisting of electrons, a circular motion. Hence the auxiliary current may be considered as made up of two general components, each one reacting with the field to strengthen the other.

The discharge only goes to the peripheral portion of the auxiliary anode 6 because of the shielding action of grids 9 on each side of the anode. Due to short spacing between these grids auxiliary anode by coating the remaining surface with an insulating substance.

Positively charged ions from annular gap I! are attracted toward the cathode surface, but due to their relatively great mass, move toward the cathode very slowly in comparison to the speed of the electrons. This motion across the magnetic field is sufficient, however, for the field to exert its force on them. Since they are current carriers, these ions will be affected in somewhat the same manner as the electrons and be given more or less of a curvilinear motion. The effect of the field on ions is, of course, very much less than that on electrons, but the curvilinear motion is sufficient to cause a rotation of ionized gas particles in the regions is and I4.

An additional factor which causes rotation of atoms and ions in regions l9 and I4 is the generally circular travel of electrons as a result of the curling of theirpath by the magnetic field. These electrons collide with atoms and ions, and whatever the nature of the collisions, whether elastic, resonant, or ionizing, result in giving atoms or ions a generally circular motion. This rotation tends to aid ions in reaching the cathode surface by virtue of centrifugal force, and favors the carriage of a larger portion of current by ions as well as tending to build up a region of high pressure along the outer portion of the region immediately adjacent the cathode surface. Such a phenomenon is a further aid to the pumping action since gas from the inner portion of the device will tend to come through annular air gap l9 and into region It.

From the foregoing it will be seen that the magnetic field operates on the discharge between the auxiliary anode 6 and the cathode I6 for imparting a gas movement in the envelope for moving gas particles toward the cathode to build up a higher pressure in the region adjacent the cathode than in the region adjacent the main anodes 5. In this way a difference in pressure is built up between these predetermined localized regions in the envelope.

The discharge between cathode surface l6 and auxiliary anode 6 is the means for causing the pumping action, and also furnishes a copious supply of electrons. This auxiliary discharge, when in operation, produces intense ionization of the gear near the cathode, and functions as a source of electrons and ions from the main discharge to the main anodes. By the connectionof the additional or main anodes and cathode I6 to transformer II, a rectified current will pass from the cathode to the main anodes. The gas in the outer region 14 being under higher pressure than in the interior of the pole pieces, will naturally tend to escape through apertures 10. The discharge between cathode surface is and main anodes 5 will take place through these apertures and be greatly aided by the gas escape, since positively charged ions in that region will neutralize repulsive forces between individual electrons, as the space charge efiect. The gas filling in the discharge thus has a pressure suflicient to produce suflicient ionization to neutralize space charge to the desired extent. Reverse current from main anodes 5 to cathode I6 or the pole pieces, which is at the same potential as the cathode, will be prevented by virtue of the difi rence in gas pressure and the short path spacing. The gas which thus flows out through the openings i0 is pumped back into the cathode region through the gap [9.

As has been stated, there is a high gas pressure in the cathode region with a low pressure in the main anode region. This is a very desirable condition since in the cathode region electrons coming from the cathode create many ions very close to the surface. These ions attract more electrons from the cathode and neutralize the tendency of the electrons to diverge in all directions. This cumulative action results in a heavy discharge or low voltage discharge between the cathode and the main anodes. In the anode region, the -low pressure militates against the possibility of reverse discharge since electrons drawn from the electrode would encounter very few atoms near the surface, and there would not be much ionization near the electrode surface.

There are two different discharges in the device, namely, between the cathode surface I6 and auxiliary anode 6, and between the cathode surface I6 and main anodes 5, along two different discharge paths and for two different purposes. The discharge between the cathode surface I6 and auxiliary anode 6 creates a copious supply of electrons, a large number of positive ions, and results in the building up of a pressure in the cathode region I4. The other discharge between the cathode surface I6 and the main anodes 5, while of much greater current intensity, is purely in the nature of a unidirectional or rectifying discharge, and contributes little, if any, to the pumping action. Main anodes 5, being in a comparatively weak magnetic field, will not have the region of great potential drop characteristic of the auxiliary anode. In fact, the entire space between the main anodes and auxiliary anode is free from extremely powerful fields, and thus is free from any artificial drops of potential or what might be termed "an artificial resistance to an intense discharge. As is well known, amagnetic field has the property of increasing the apparent resistance of a gas discharge space, and unless the potential is sufiicient, may blow out the discharge. Hence, the magnetic field in the gap I9 greatly increases the potential drop between the auxiliary electrode 6 and the cathode, and a sufliciently great potential between the cathode surface I6 and auxiliary anode 6 is necessary in order to maintain the discharge in spite of the very intense magnetic field. The discharge path from cathode surface Hi to main anodes 5, however, is substantially magnetic field-free, does not have this artificial resistance, and hence has a very much lower drop than the auxiliary discharge.

As shown, coil 3 is connected so that the main discharge current traverses it as well as the load I2. In this instance, coil 3 would become more powerfully energized as the main discharge current increased in intensity, the increase of the field intensity increasing in turn the currentcarrying capacity of the main discharge. By having the two fields in opposition and connecting inductance and capacity, the tube can be made to oscillate. The tube may also be caused to amplify by having input currents traverse coil 3.

While I prefer to initiate the discharge by means of 'a thermionic cathode, it is possible to start the discharge directly from cathode surface I6 of casing I. In such a case, it is essential that there be some free gas or vapor. If only caesium is used, the tube may be warmed to about 75 C. to obtain a supply of vapor. If a gas is used in conjunction with caesium, the discharge will start through the gas and warm up the tube. The potential necessary to initiate a discharge without filament I5 may be higher, but once the discharge has started, it will continue at the ordinary I5, the difference in potential between it and casing I will initiate a discharge to the casing, thus causing the auxiliary discharge to occur. The casing will thus have ions near it creating a condition which is conducive to the participation of region I6 of the casing in the discharge.

Instead of making the walls of the member IS the main cathode surface, the surface of a thermionic cathode similar to cathode I5 in Fig. 1 may be made the main cathode surface. Such an arrangement is shown in Fig. 3. In this figure similar reference numerals to those used in Fig. 1 with the addition of a prime are applied to those members which correspond to similar members in Fig. 1. Thus in Fig. 3 the device shown consists of a casing I supporting two annular magnetic pole pieces, each comprising a cylindrical portion 2' and a ring portion 2|. The two main anodes 5' are each supported preferably on an individual glass stem or press 33 sealed into the lower end of casing I in a manner similar to that of press 8 in Fig. 1. Each glass stem 33 is likewise provided with a tubular portion 34 surrounding and shielding the respective anode-supporting wire 35. The auxiliary anode 6' is mounted on a reentrant glass press 32, and its lead wire is protected by an insulator 'I' in the same manner as described in connection with Fig. 1. The shielding grids 9 are likewise provided as described above. It also may be desirable to separate the two anodes 5' from each other by means of a partition extending across the tube below the auxiliary anode 6' in a plane at right angles to that shown in Fig. 3. This partition could be supported by the auxiliary anode-supporting structure. Within the cathode chamber formed by the ring portions 2| are placed one or more filamentary cathodes 36. In Fig. 3 there are shown two such cathodes each placed adjacent the openings III in the lower ring 2| opposite which the anodes 5 are located. These filamentary cathodes may be made of any-suitable material which emits electrons thermionically at a relatively high temperature. This material may be a bare refractory metal, such as tungsten. However, in some. cases it may be desirable to coat the filamentary cathodes 36 with ele'ctron-emissive material, such as, for example, the alkaline earth oxides.

upper ring 2| as they pass through it either by passing through an opening therein, such as shown in Fig. 1, or by an insulating plug member 31, such as shown in Fig. 3. The lead wires for the respective cathodes 36 are sealed in reentrant glass presses 38 which are in turn sealed in the upper end of the casing I. The arrangement as shown in Fig. 3 may be filled with any of the gases or vapors specified in connection with Fig. 1, although I prefer in this arrangement to use mercury vapor.

As in the case of Fig. l, the device is provided with a permanent magnet 4', only the ends of which are shown in Fig. 3, and also with a coil 3. The filamentary cathodes 36 are each provided The lead wires extending from the fila-. mentary cathodes 36 may be insulated from the with heating current from end portions 39 of the secondary 43 of 'a transformer 44, whereby the relatively extended electron-emitting surfaces of the cathodes 36 are heated to temperature of thermionic emission independent of a discharge in said device for producing an electron discharge to the anodes during operation. The secondary 43 is provided with a center tap which is connected by means of a conductor 41 through a resistance 45 .to the casing ,I. The two central portions 46 of the secondary 43 supply a potential diflerence between the. casing I and the cathodes 36 so as to cause a current to flow between the cathodes 36 and the casing I. The resistance 45 is provided to limit this current to any desired value, and in some instances the resistance 45 may be omitted entirely. The flow of current between the cathodes 36 and the portion of the easing I within the cathode chamber ionizes the gas or vapor within the cathode chamber, thus producing ions for the purpose as specified in connection with Fig. 1. In order to produce the pumping action described above, a conductor 21' connects the auxiliary anode 6' through a regulating resistance l3 to the positive terminal of a battery 48, the negative terminal of which is connected by means of a conductor 26 to the conductor 41. In this manner the potential of the battery 48 is impressed between the cathodes 36 and the auxiliary anode 6' to produce the auxiliary discharge which causes the pumping action described above to be produced. A load transformer II' has the outer terminals of its secondary winding 49 connected by means of the conductors 23' and 24' to the anodes 6', respectively. A conductor 50 extends from a centertap on the secondary 49 through the load l2, and the .coil'3 to the conductor 41. In this way the secondary winding 49 produces a potential difference between the cathodes 36 and the anodes 5' which causes a current to flow within the tube in such a manner that a rectified load current passes through the load I2 and the coil 3.

The operation of the arrangement shown in Fig. 3 is substantially identical with that as described in Fig. 1, the pumping action producing a higher pressure in the cathode region than in the anode region. However, in Fig. 3, the main source of electrons for carrying the main load current comes from the cathodes 36. In this way large amounts of current can be carried at a relatively low voltage drop. The transformers 44 and II' may be energized from the same source of alternating potential. It is also preferable to arrange the phase of these two transformers so that when an anode 5' is positive with respect to the cathodes 36adjacent to it so that a discharge tends to fiow, the voltage in the secondary winding 43 is in such a direction so as to make that cathode 36 negative with respect to the easing l, and therefore to the ring portions 2|. In this way the interposition of the ring portions 2 I between the cathode 36 and its respective anode will not have any tendency to impede the starting of the discharge. Even though the phase arrangement is otherwise than that described above, one of the cathodes 36 will always be negative with respect to the ring portions 2|, andtherefore any tendency for the ring portions 2| to impede the starting of the discharge will be substantially eliminated. Although in Fig. 3 I have shown two cathodes 36, but a single such cathode could be provided in which case the discharge to each anode would come from the same cathode surface. As a matter of fact, in Fig. 3 it is possible that both cathodes 36 contribute to the discharge to each of the anodes 5.

Although in Figs. 1 and 3 the tube is shown as a full-wave rectifier tube, it might be desirable in some instances to have the device arranged as a single anode, half-wave rectifier. An example of such an arrangement is shown in Fig. 4. In Fig. 4 as in Fig. 1 the device is composed of a casing ll carrying two annular magnetic pole 75 pieces, each comprising a cylindrical portion 202 nection with Fig. 1.

' the same manner as is the filament l5 shown in Fig. 1. The lead wires for the filament 2i5 are sealed in a reentrant press 222, and the filament 2I5 is energized by portion 240 of the secondary of transformer 220. The portion 242 of the secondary of transformer 220 applies a difference in potential between filament 2 l5 and the casing l0! to initiate a discharge for the purpose of creating ions in the cathode region as described in con- The main cathode surface in Fig. 4 is provided by a thermionic filament 236 which may be of the same type as the thermionic filaments in Fig. 3. The filament 236 is located within the cathode chamber formed by the ring portions 22L The lead wires for said filament pass through the upper ring portion HI, and are insulated therefrom by some suitable means, such as an insulating plug 231. These lead wires are likewise sealed in a reentrant glass press 238 which is also sealed in the upper end, of casing IN. A single anode 205 is provided adjacent an opening 210 in the upper ring portion 22I through which opening a discharge can pass between the cathode 236 and the anode 205. This anode is supported on a lead wire 223 which is sealed in a reentrant glass press 208 also sealed in the upper end of easing l0l.- The tube may be filled with some suitable gas or vapor, such as that described in connection with Figs. 1 and 3.

The tube shown in Fig. 4 is provided with a permanent magnet 204, the ends only of which are shown in Fig. 4, and with-a coil 203 in the same manner as in Figs. 1 and 3. The filament 236 is supplied with heating current. from the secondary 239 of a transformer 244. The secondary 239 is provided with a center tap 241 which is connected directly to-the casing |0| so that said cathode and casing are substantially at the same potential. A load transformer 2 has one end of its secondary winding 225 connected to the center tap 241, the other end of said secondary being connected through the coil 203 and the load M2 to the anode 205 through the anode lead 223. Thus when a discharge fiows between the oathode 236 and the anode 205, the current supplied from the secondary winding 225 is rectified, and this rectified current passes through the load 2l2 and also the coil 203. The pumping of the gases within the tube so as to create a high pressure adjacent the cathode 236 and the accompanying operation of the tube are the same as that discussed in connection with Figs. 1 and 3.

My invention thus comprises a device in which an auxiliary discharge and a magneticfield combine to pump gas particles into a region, and thus build up a high pressure there. Due to the construction of the device, the auxiliary discharge is attended by an unusually large amount of ionization, consequent generation of a large number of electrons and positively charged ions, and thus to emit electrons, an anode spaced therefrom, means for establishing a magnetic field, the lines of force of which are substantially perpendicular to the normal electron paths from the cathode to the anode, means for concentrating the lines of force into a narrow annular region between the cathode and anode, and additional anodes spaced from the cathode.

2. A gaseous conduction device comprising a metal container having a generally cylindrical shape, circular magnetic pole pieces maintained within said container and separated by a gap, an anode located in said gap, and means for establishing a magnetic field across said pole pieces and across said gap, said anode adapted to cooperate with an interior portion of said container to maintain an auxiliary discharge in the normal operation of the device, and another anode, said auxiliary discharge when in operation functioning as a source of electrons and ions for the main discharge to said last-named anode.

3. A space current device comprising an evacuated envelope having a gas filling, a cathode having an electron-emitting surface in said envelope, a main anode in said envelope to maintain a discharge with said cathode, an auxiliary anode in said envelope to maintain a discharge with said cathode surface, enclosure means for restricting the discharge between said auxiliary anode and said cathode to a confined region, and means for acting on the discharge through said region to limit the current to said auxiliary anode to a low value while maintaining a high voltage gradient in said region to secure intense ionization of the gas near said cathode.

4. A space current device comprising an evacuated envelope having a gas filling, a cathode having an electron-emitting surface in said envelope, 9. main anode in said envelope to maintain a discharge with said cathode, an auxiliary anode in said envelope to mantain a discharge with said cathode surface, enclosure means for restricting the discharge between said auxiliary anode and said cathode to a confined region, and means for acting on the discharge through said region to limit the current to said auxiliary anode to a low value and secure a high voltage gradient in said region and to maintain adjacent said cathode surface a body of ionized gas of higher pressure than the region around said main anode.

5. A space current device comprising an evacuated envelope having a gas filling, a cathode having an electron-emitting surface in said envelope, an auxiliary anodein said envelope to maintain a discharge with said cathode, enclosure means for restricting the discharge between said anode and said cathode to a confined region, magnetic means for acting on the discharge through said region to impart to the electrons movement over relatively extended paths, impeding their fiow towards the anode and producing intense ionization of the gas in said region, and a main anode outside said confined region for maintaining a discharge with said cathode.

6. A space current device comprising an evacuated envelope having a gas filling, a cathode having an electron-emitting surface in said envelope, an auxiliary anode in said envelope to maintain a discharge with said cathode, enclosure means for restricting the discharge between said anode and said cathode to a confined region, means for producing a magnetic field extending transversely to the direction of the discharge path through said confined region for imparting to the electrons that may pass through said region a movement along lengthened paths, impeding their flow to the anode and for producing ionization of the gas in said region, whereby a highly ionized body of gas and a high voltage gradient is maintained in said region, and a main anode outside said confined region for maintaining a discharge with said cathode.

7. A space current device comprising an evacuated envelope having a gas filling, a cathode having a thermionically electron-emitting surface in said envelope, an anode in said envelope to maintain a discharge with said cathode, enclosure means constituting a chamber enclosing the space in front of said cathode-emitting surface and separating said space from the anode space, said enclosure means having a restricted opening through which electrons from said cathode may pass to said anode, and means for imparting to the electrons that may pass through the region of said opening movements along lengthened paths at which appreciable positive ionization is produced in said region and the fiow of electrons to said anode is impeded.

8. A space current device comprising an evacuated envelope having a gas filling, a cathode having a thermionically electron-emitting surface in said envelope, an anode in said envelope to maintain a discharge with said cathode, enclosure means constituting a chamber enclosing the space in front of said cathode-emitting surface and separating said space from the anode space, said enclosure means having a restricted opening through which electrons from' said cathode may pass to said anode, and means for producing a magnetic fiux transversely to the direction of the discharge through said opening and imparting to the electrons in said region movements along elongated paths at which appreciable positive ionization is produced in said region while impeding the fiow of electrons to said anode to maintain in said region a body of highly ionized gas at a high voltage gradient in the direction between said cathode and said anode.

9. A space current device comprising an evacuated envelope having a gas filling, a cathode having an electron-emitting surface in said envelope, an anode in said envelope to maintain a discharge with said cathode, enclosure means constituting a chamber enclosing the space in front of said cathode-emitting surface and separating said space from the anode space, said enclosure means having a restricted opening through which electrons from said cathode may pass to said anode, means for imparting to the electrons that may pass through the region of said opening movements along lengthened paths at which appreciable positive ionization is produced in said region and the flow of electrons to said anode is impeded, and an additional anode within said envelope outside the chamber formed'around said cathode to maintain a discharge with the space enclosed around said cathode.

10. A space current device comprising an evacuated envelope having a gas filling, a cathode having an electron-emitting surface in said envelope, an anode in said envelope to maintain a discharge with said cathode, enclosure means constituting a chamber enclosing the space in front of said cathode-emitting surface and separating said space from the anode space, said enclosure means having a restricted opening through which electrons from said cathode may the electrons in said region movements along elongated paths at which appreciable positive ionization is produced in said region while impeding the flow of electrons to said anode to maintain in said region a body of highly ionized gas at a high voltage gradient in the direction between said cathode and said anode, and an additional anode within said envelope outside the chamber formed around said cathode to maintain a discharge with the space enclosed around said cathode.

11. A space current device comprising an evacuated envelope having an ionizable gas filling at a pressure sufficient to produce suificient ionization to neutralize space charge, a cathode having an electron-emitting surface in said envelope, a main anode in said envelope to maintain a discharge with said cathode, an auxiliary anode in said envelope to maintain a discharge with said cathode surface, means for lengthening the path of electrons and ions passing between said cathode surface and said auxiliary anode and for greatly increasing the potential drop between said auxiliary anode and said cathode.

12. A space current device comprising an evacuated envelope having an ionizable gas filling at a pressure suificient to produce sufficient ionization to neutralize space charge, a cathode having an electron-emitting surface in said envelope, a main anode in said envelope to maintain a discharge with said cathode, an auxiliary anode in said envelope to maintain a discharge with said cathode surface, and magnetic means for lengthening the path of electrons and ions passing between said cathode surface and said auxiliary anode and for greatly increasing the potential drop between said auxiliary anode and said cathode.

1 3. A space current device comprising an evacuated envelope having a gas filling, a cathode having an electron-emitting surface in said envelope, a main anode in said envelope to maintain a discharge with said cathode, an auxiliary anode in said envelope to maintain a discharge with said cathode surface, and means for distorting the normal potential distribution between said cathode and auxiliary anode, creating the greatest drop of potential adjacent the auxiliary anode.

14. A space current device comprising an evacuated envelope having a gas filling, a cathode having an electron-emitting surface in said envelope, a main anode in said envelope to maintain a discharge with said cathode, an auxiliary anode in said envelope to maintain a discharge with said cathode surface, and magnetic means for distorting the normal potential distribution between said cathode and auxiliary anode, creating the greatest drop of potential adjacent the auxiliary anode.

15. A space current device comprising an evacuated envelope having a gas filling, a cathode in said envelope, a main anode in said envelope to maintain a discharge with said cathode along a discharge path, an auxiliary anode in said envelope to maintain a discharge with said cathode along another discharge path, an auxiliary electrode to maintain an ionizing discharge with said cathode for moving gas particles toward the cathode to build up a higher pressure in the region adjacent the cathode than in the region adjacent the anode.

16. A space current device comprising an evacuated envelope having a gas filling, a cathode in said envelope, a main anode in said 'envelope' to maintain a discharge with said cathode along a discharge path, an auxiliary anode in said envelope to maintain a discharge with said cathode along another discharge path, an auxiliary electrode to maintain an ionizing discharge with said cathode for supplying ions to the discharge between said auxiliary anode and said cathode, meansfor separating the region adjacent the cathode from the region adjacent the main anode and having a discharge opening for allowing the discharge to pass, and magnetic means operating on the current carriers in the discharge between said auxiliary anode and said cathode for moving gas particles toward the cathode to build up a higher pressure in the region adjacent the oathode than in the region adjacent the anode.

17. A space current device comprising an evacuated envelope having a gas filling, a cathode having an electron-emitting surface in said envelope, means independent of a discharge in said device for heating said surface to temperature of thermionic emission, an auxiliary anode in said envelope to maintain a discharge with said cathode, enclosure means for restricting the discharge between said anode and said cathode to a confined region, magnetic means for acting on the discharge through said region to impart to the electron movement over relatively extended paths, impeding their flow towards the anode and producing intense ionization of the gas in said region, and a main anode outside said confined region for maintaining a discharge with said cathode.

18. A unidirectional gaseous discharge device comprising an evacuated envelope containing gas, an anode, a cathode having an extended discharge surface, means independent of a' discharge in said device for heating said surface to temperature of thermionic emission for producing an electron discharge to said anode during operation, and means for producing a magnetic field in the discharge space between said cathode surface and said anode to impart a gas movement in said envelope for producing. a high pressure in the region adjacent said cathode surface, whereby a low voltage discharge may be maintained between said cathode surface and said anode.

19. A space current device comprising an envelope having a gas filling, a cathode in said envelope, means independent of a discharge in said device for heating said cathode to temperature of thermionic emission, a main anode in said envelope to maintain a discharge with said cathode along a discharge path, an auxiliary electrode in said envelope to produce a discharge with said cathode along another discharge path, and means for operating on the discharge between said auxiliary electrode and said cathode for moving gas particles toward the cathode to build up a higher pressure in the region adjacent the cathode than in the region adjacent the anode.

20. A space current device comprising an envelope having a gas filling, a cathode in said envelope, a main anode in said envelope to maintain a discharge with said cathode along a discharge path, an auxiliary electrode in said envelope to other discharge path, and means for creating produce a discharge with said cathode along an- .velope having a gas filling, a cathode in said envelope, means independent of a discharge in said device for heating said cathode to temperature of thermionic emission, an anode in said en'velopeto produce a discharge with said cathode along a discharge path, and magnetic means for operating on the discharge between said anode and said cathode in such a way as to create a difierence in pressure between predetermined localized regions in said envelope.

22. A space current device comprising an envelope having a gas filling, a cathode in said envelope, means independent of a discharge in said device for heating said cathode to temperature of thermionic emission, an anode in said envelope to maintain a discharge with said cathode along a discharge path, an auxiliary elec-- trode in said envelope to produce a discharge with said cathode along another discharge path, and magnetic-means for operating on the discharge between said auxiliary electrode and said cathode in such a way as to create a difference in pressure between predetermined localized regions 15 in said envelope.

CHARLES G. SMITH.