US2138518A - Gaseous conduction apparatus - Google Patents

Description

Nov. 29, 1938.

C. G. SMITH GAsEoUs coNDUcTIoN APPARATUS Original Filed May 28, 1928 different planes.

Patented Nov. 29, 1938 UNITED STATES PATENT OFFICE 2,138,518 GAsEoUs coNnUc'rroN APPARATUS` Delaware Application May 28, 1928, Serial No. 281,175 Renewed November 23, 1933 23 Claims.

My invention relates to electrical discharge apparatus and has particular reference to that type of apparatus which is accompanied by a discharge of electricity through a gas or a vapor.

According to modern ideas in physics, every element or substance has as its ultimate unit an atom. The atom is composed of a central body or nucleus which is positively charged. With this nucleus as a focal center, each atom has a large number of electrons in different orbits and in All electrons in a neutral atom are in equilibrium with the positive nucleus. Many, ifnot most, of the electrons of an atom are disposed comparatively close to the central body. The remaining electrons, however, are disposed in orbits which have a comparatively great dimension compared to the actual size of the nucleus or the electron itself. The atom with all its electrons revolving about this forms a unit, the volume of which is exceedingly great compared to the actual volume of all the particles.

Considering the atomic structure as above, a discharge through gas is usually considered to be accompanied by the phenomenon called ionization. In a general way, the mechanism of this is as follows:-An electron starting out from a certain point in space is accelerated by the potential gradient existing in that space and tends to fall through the potential gradient along the lines of electrostatic force. When this happens, in a space in which there are atoms and molecules in continuous and casual motion, as is the case when a gas or a vapor is present, the electron in falling through the potential gradient, is apt to go through a portion of the space included within the atom. This is considered to be a collision. As far as actual physical impact between the free electron and the atomic electron is concerned, there is a very small chance of that happening.

As has been stated above, the volume of an atom compared with the actual volume of the particles is very great. Calculation and actual experiment have shown that actual physical impact between moving electrons and the physical portions of the atom is very rare and does not comprise in its entirty what is meant by the term "collision. When a collision occurs, it is simply that the spheres of infiuence of both the moving electrons and the electrons or nucleus of the atom have intersected and allow of the interplay and interaction of electrostatic and electro-magnetic forces.

Collisions may be of several kinds. Where an electron is falling through a very steep potential gradient, it is accelerated very greatly. If this electron collides with an atom before it attains very great speedin other words, before it has been able to fall through a considerable portion of the difference in potential-the collision may be regarded as like that of two rubber balls in which the electron and the atom will rebound. This is an elastic collision.

The electron will again be impelled by the electrostatic eld to dropdown the potential gradient and this time it may be able to get up somewhat greater speed and have greater momentum before it has another collision. In this second collision, one of the electrons moving in its orbit in the atom may be so shaken and jarred that it falls into an outer orbit, the entire atom thus absorbing a certain so called quanta of energy. The potential through which the striking electron has fallen to cause such a phenomenon ls called the resonance potential. The atom which has its electron in an outer orbit is in a so-called excited state and is very unstable. The electron drops back from the outer orbit to an inner orbit with the evolution of an amount of energy equivalent to that absorbed from the striking electron. This evolution of energy is made evident by a tiny flash of light of a particular frequency. This frequency is dependent entirely upon which particular orbit the electron left and which one it landed into.

From such a collision, the electron will start again and be caused to fall through the potential gradient by the electrostatic field-assuming, of course, that it has not fallen through the entire diierence is potential. The free electron may now perhaps fall through such a great potential drop that by the time it has its third collision, it will have been traveling at a much greater speed than before. This time the collision between the atom and the electron is so violent as to dislodge at least one of the electrons from the previously neutral atom. The free electron, of course, goes on its way as before, following an unsteady and tortuous course. The atom which has now lost one of its electrons is positively charged due to the preponderant and unneutralized charge of the nucleus.

The'potential drop through whichv an electron must fall to create ions from neutral atoms is called the ionizing potential. It is perfectly possible for collisions of higher order both as regards resonance and ionization to occur. Thus, a sufficiently great potential drop will so accelerate an electron that it has sufficient energy to dislodge an electron from anion and deprive the formerly neutral atom of two electrons.

The potential necessary for the above effect varies with the nature of the atom. Of course, it is to be understood that with a given potential dinerence, some electrons may have only one type of collisions in falling down the potential gradient. or may have several different kinds. 'I'he entire discharge is merely the average for all the electron collisions at a particular instant.

A moving electron or a moving electron stream is the equivalent of a current of electricity and behaves very much like it in the presence of a magnetic ileld. Modern researches have shown that the electrons about the nucleus of an atom are like a tiny current of electricity and appear to endow the atom with the properties of a little magnet. Experiments have been made using silver atoms and powerful magnetic fields which indicate that under the innuence of such elds, the atoms orientate themselves in certain positions. Thus, half of them appear to align themselves with the lines of force of the iield in kone or several deiinite directions while the other half appears to similarly align in opposite directions.

Of all atoms known, those of the alkali metal group have the very peculiar property of having enormously larger volume than the rest. Of this group, lithium has the smallest volume, the minimum increasing with each member of the group until a maximum is reached as in the case of caesium. It appears that these alkali metals have at least one electron which has an orbit enormously greater than any of the other orbits and which results in the atom having such an enormously great volume.

By lmy invention I make use of the phenomenon of the orientation of the atoms and molecules by a magnetic field to create targets for the speeding electrons, the targets being so much greater than ordinarily would be the case as to result in an enormous increase in the number of collisions. In a general way, I provide a device in which I preferably dispose vapor of one of the alkali metals, such as caesium, with a means for emitting electrons within the device and a means for creating a magnetic field, all related to effect the result above stated.

The magnetic field crowds the electrons into a comparatively narrow and dense stream, and at the same time, orientates the gas particles. 'I'he orientation off the gas particles is such that there is probably a maximum of electronic orbital surface, perpendicular to the lines of force of the field. Thus, in the case of alkali metals, the atoms are so disposed that their outermost orbits are probably substantially perpendicular to the lines of force, whereas ordinarily the atoms are disposed in a casual manner, always changing their large orbital planes due to their` ceaseless motion. 'I'he eld appears to create an arrangement of the molecules, so disposed that they present excellent targets for electrons traveling in the direction of the lines of force of the magnetic eld.

The electron stream being concentrated appears to cause an enormous ionization in its path. The ions of the gas particles having so much more mass than the electrons-in the case of caesium, the ratio being 230,000 to l-are substantially unaffected by the electrostatic field and move very sluggishly in comparison to the electrons. Since the ions have a positive charge, they are strongly attracted to the electrons but 'the electrons are constricted to a narrow Stream susana by the magnetic iield. The result is that the ions are retained in that electron stream by the attraction and thus neutralize the repulsive forces among the electrons themselves-the so called space charge effect. Thus, the magnetic field' arranges'the atoms to form better targets, converges the electron stream to a beam in spite of the tendency of the electrons themselves to diverge and secondarily, causes a large number of ions to be present in the electron stream to neutralize' the space charge and themselves to further ionized.

Referring to the drawing, Figures l and 2 show two preferred embodiments of my invention.

Figures 3 and 4 are transverse sectionahviews of Figures 1 and 2 respectively.

Referring to Figures 1 and 3, a glass container is shown of a relatively long and tubular shape. This container is, of course, thoroughly exhausted and free of impurities. At one end is sealed a cathode 2, here shown as of the lamentary thermionic type. At the other end is a capsule 5 containing the necessary chemicals for the liberation of a conducting vapor. Preferably-I use caesium vapor. Supported by two wires 9 and I0 sealed into the glasscontainer is an anode 4, here shown as disc shaped, but which may be of any shape whatever, provided there is suilicient transverse surface for proper functioning. At the other end of the two wires is a ring or annular shaped auxiliary electrode 3 at the same potential as electrode 4. This auxiliary electrode 3 is preferably such a distance from cathode 2 that under normal conditions any electrons leaving electrode 2 would not have a suillcient number of collisions with the gas particles before reaching 3 to cause any substantial ionization. On reverse current, when electrodes 3 and 4 would tend to become cathodes and 2 an anode, the gap between 2 and 3 becomes practically insulating and the few electrons thus emitted from 3 and 4 result in practically no conduction, the potential being concentrated between the auxiliary electrode 3 and the cathode. i is a coil whose axis is in substantial coincidence with the axis of the tube and `fwhich, upon suitable energization by some source of direct current,l gives a magnetic field.

'I'he operation of the tube is as follows:-Cath ode 2 upon suitable energization by direct or alternating current is heated so that it emits electrons. A suitable source of direct current is connected to coil l while a source of discharge current is connected between the anode 4 and the cathode 2. This latter source of current may be either direct or alternating. In the case of alternating current, rectication will occur with consequent suppression of the reverse cycle. Electrons emitted from cathode 2 will not go to electrode 3 as might ordinarily be the case but will tend to follow the lines of force of the magnetic field. Thus, any electrons emitted from 2 whichn would otherwise go to 3, would be crossing magnetic lines of force which tendency is resisted by the actionof the field upon the electrons. The result is that all of the electrons emitted from 2, in spite of their mutual repulsion and tendency to diverge, will be constricted into a stream, in this case substantially coincident with the axis of the tube. 'Ihis stream of electrons will therefore, go to anode, 4 instead of to the equi potential electrode 3. Under normal temperatures, caesium has suiilcient vapor pressure When the magnetic field, due to coil i, is suiliciently strong, these atoms probably become orientated so that they present a series of broad flat targets, perpendicular to the direction of the electron stream. The exceedingly intense ionization in this constricted stream of electrons becomes evident by a very intense glow of the caesium spectrum. The appearance of the caesium spectrum is, of course, as explained, on the hypothesis that there are an enormous number of non-ionizing collisions in which electrons have merely fallen through the resonant drop of potential for caesium in addition to the ionizing collisions. The return of the electrons to theiroriginal orbits in the caesium atoms in this narrow region is accompanied by the emission of a flash of light whose frequency is in the spectrum of caesium. The enormous number of such collisions gives rise to an intense caesium glow.

In the stream of electrons as evidenced by the glow, in this case, of caesium spectrum, there is an enormous number of excited atoms. As has been stated above, these excited atoms are atoms in which an electron has been displaced from its orbit into an outer orbit. Upon the falling of the electron from the outer orbit to the inner orbit, a glow of characteristic frequency is emitted, but during the time when the atom is excited-that is, during the time when the electron is in the outer orbit, the atom presents a larger target than is normally the case. Furthermore, it is obvious that an electron in such a state does not require as violent a collision to dislodge the electron entirely-that is, to ionize the atom as is the case with ordinary neutral atoms. Hence, in this narrow stream of electrons is present, as is made evident by the intensity of the glow, an enormous number of excited atoms which not only present larger targets than is ordinarily the case, but targets which do not require as much of a drop of potential through which an electron must fall to ionize them.

In operating a tube of this construction filled .with caesium at about 'l5 degrees centigrade (corresponding to a vapor pressure of about 10-4 mm.), I found that as the magnetic field produced by the coil I was gradually increased, the voltage drop between the cathode 2 and the anode -4 decreased until at a field strength of about 50 gauss the voltage drop came down to about 500 volts. As the current in coil I was increased, making the field stronger, the voltage drop came down abruptly from 500 volts to 5 volts. Simultaneously with the sudden drop across the tube, an intense glow, characteristic of the tube when operating, became evident. The gradual reduction of the drop across the cathode and anode of the tube as the field strength was increased, may be explained upon the basis of an increasingly larger number of the gas atoms which were orientated and thus made better targets for the electron stream. The critical change is probably due to the final overcoming of what might be termed an atomic inertia and the orientation of all the atoms. As is well known, a somewhat similar phenomenon is present in the magnetization of iron and like materials, where with a gradually increasing magnetizing force, the magnetic flux gradually increases until a certain unstable point is reached when an enormous in-v is perpendicular to the axis loi. coil I. With `both coils I and energized, the resultant eld will be at an angle to the axes of both coils. By making thefield due to 1 stronger than I, the original field due to I, whose axis substantially coincides with the axis of the tube, will 'gradually be tilted to an oblique position.

The grid 8 joining anode ,4 and ring 3 is really an anode portion in itself but so disposed that the electron stream'from cathode 2 may be diverted from its longest path to take shorter paths and still strike an anode portion to complete the current carrying circuit through the tube. The electrons emitted from cathode 2 will follow the lines of force of the field and if the eld be tilted from the axis very much, the stream will be diverted from the axis and impinge upon grid 8. The greater the diversion, the nearer toward ring 3 will the stream strike the grid B. The path of the stream thus being gradually shortened will naturally result in less ionization since there will be fewer collisions. By making the field of l so much more powerful than I as to deflect the stream from cathode 2 to the neighborhood of ring 3, it is possible to cut down the current going through the tube and at the same time, increase the potential drop across the tube very greatly.

By suitable connections of capacity and inductance with the tube and coil 1 so that the main discharge current through the tube traverses coil l, inductance, and capacity, the tube may be made to oscillate. It is also possible to cause the tube to amplify by connecting coil I to a source of current which is to be amplified, this current, as it increases, straightening out the electron stream and thus increasing the ionization in the tube and the current through the tube.

Thus it will be seen that I Vhave devised an apparatus in which with a given gas content and a given electron stream, the ionization of the gas content by the electron stream is enormously increased over what is possible in ordinary gaseous conduction apparatus. The anode and the cathode are so arranged within the tube that in the absence of a proper field the discharge through the tube is negligible. By properly adjusting the field between the cathode and the anode, the tube may be rendered highly conductive to produce discharges with a voltage drop of the order of five volts, although on account of the low pressure within the tube it withstands high back voltages. The auxiliary electrode 3 concentrates the voltage gradient inthe tube in the space between the cathode and the auxiliary electrode and causes the voltage gradient along the major portion of the electron paths towards the anode to be relatively low. When the field is of, the low voltage gradient in the space between the auxiliary electrode and the anode is instrumental in holding down positive ionization, thereby assisting in maintaining low,

conductivity through the tube. When the field is on, the electrons coming from the cathode become highly accelerated due to the high voltage gradient in the initial part of the electron path. so that in their further fiow along the path determined by the magnetic field, they produce sufficient positive ionization to overcome the space charge and secure the high conductivity of the tube. l

In the foregoing I also attempted to give an explanation of the reasons underlying the operation of the improved tube as understood by me. I do not desire, however, to limit my invention to any particular theory since reasons other than those stated by me may be nsible for .the 'novel operating characteristics of the tube ofmy invention. I accordingly desire that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

I claim: 1. A space discharge device comprising a gastight vessel containing a thermionic cathode and an anode separated bya path of substantial distance, magnetic means for producing a ux in said path and parallel thereto, and a gas in said vessel, said path being suiilciently long and said gas during operation being maintained at a pressure suiilcientiy low to prevent appreciable ionization of the gas from occurring and an appreciable current from passing between said anode and cathode at applied voltages in excess of ionization voltages of the gas in absence oi said magnetic flux, said pressure being sufficiently high, however, to produce, in the presence of said magnetic iiux, copious ionization of said gas through said path sufficient to maintain a relatively large space current between said cathode and anode at a voltage of the order of the ionization voltage of the gas or less.

2. A space discharge device comprising a gastight vessel containing a thermionic cathode, and an anode separated by a path of substantial distance, said vessel having interior walls connning the discharge p'ath and adapted to receive electric charges having a controlling effect on the space current, a gas in said vessel, and magnetic means for producing a ux in said path and parallel thereto concentrating the electron ow along said confined path away from the walls, said gas during operating being maintained at a pressure suiliciently low to prevent appreciable ionization of the gas from occurring and an appreciable current from passing between saidA anode and cathode at applied voltages in excess of ionization voltages of the gas in absence of said magnetic flux, said pressure being suillciently high, however, to produce, in the presence of said magnetic ilux, copious ionization of said gas through said path suiicient to maintain a relatively large space current between said cathode and anode at a voltage of the order of the ionization voltage of the gas or less.

v3. A space discharge device comprising a gastight vessel containing a thermionic cathode, and an anode separated by a path of substantial distance, magnetic means for producing a ilux in said path and parallel thereto, and a gas in saidvessel, said gas during operation being maintained at a pressureof the order of 10-4 mm., said path being suiliciently long at the op-l erating pressure of the gas to prevent appreciable ionization of the gas from occurring and an appreciable current from passing between said anode and cathode at applied voltages in excess of ionization voltages of the gas in absence of said magnetic ux,l said pressure being sumciently high, however, to produce, in the presence of said magnetic ux, copious ionization of said gas through said path between said cathode and anode.

4. -A space discharge device comprising a gastight vessel containing a thermionic cathode, and an anode element separated from said cathode by a path of substantial distance, a gas in said vessel, an auxiliary electrode element disposed along said path within a distance from said cathode insumcient to produce ionization of the gas under appliedpotentials in excess of ionizaandere tion voltages oi.' ,the gas. and magnetic means for producing a ux in said path-and parallel thereto, said pathI being sumciently long and said gas during operation `being maintained. at a pressure sumciently low to prevent appreciable ionization o! the gas from occurring and an appreciable current from passing between said anode element and cathode at applied voltages in excess of ionization voltages of the gas in absence oi' said magnetic ux, said pressure being sumciently high. however, to produce, in the presence of said magnetic Ilux, copious ionization of said gas through said path.

5. A space discharge device comprising a gastight vessel containing a thermionic cathode, and an anode element separated from said cathode by a path o! substantial distance, a gas in said vessel, an auxiliary electrode element disposed along said path, and magnetic means for producing a ilux in said path and parallel thereto concentrating the electron flow along said path away from said auxiliary electrode element and toward said anode, the distance of said auxiliary electrode element from said cathode being sumciently small and the gas pressure being suiiiciently low to cause substantially all of the electrons ilowing from said cathode to pass from said cathode to said auxiliary electrode element without substantial ionization under applied potentials in excess of ionization voltages of the gas in absence of said magnetic eld.

6. A space discharge device comprising a gastight vessel containing a cathode and an anode separated by a path of substantial distance, magnetic means for producing a flux inl said path and coaxial therewith, a gas in said vessel, said gas during operation being maintained at a pressure sumciently low to prevent an appreciable current from passing between said anode and cathode at applied voltages in excess of ionization voltages of the gas in absence of said magnetic flux, said pressure being sumciently high how ever, to producein the presence of said magnetic iiux substantial ionization and conduction of current through said path at a voltage of the order of the ionization voltage of the gas or less.

7. A space discharge device comprising a gastight vessel containing a cathode and an anode separated by a path of substantial distance, a gas in said vessel, magnetic means for producing a flux in said path coaxial therewith, said gas during operation being maintained at a pressure suiiciently high to produce in the presence of said magnetic iiux copious ionization of said gas and substantial conduction of current through said path at a voltage of the order of the ionization voltage of the gas or less, said gas pressure being suiliciently low so that upon a decrease of the magnetic ilux below a minimum value, substantial ionization and conduction of current between said cathode and anode cease at voltages in excess of the ionization voltage of the gas.

, 8. A space discharge device comprising a gastight vessel containing a cathode and an anode separated by a path of substantial distance, a gas in said vessel, said gas during operation being maintained ata. pressure suflciently high to produce, upon passage oi electrons from said cathode to said anode, copious ionization and conduction of current at a voltage of the order of the ionization voltage of the gas or less, and mag'- tain said ionization and conduction of current,

said gas pressure being suiciently low so that upon a decrease of the magnetic iiux, below a minimum value, substantial ionization and conduction of current between said cathode and anode cease at voltages in excess Aoi? the ionization voltage of the gas.

9. A space discharge device comprising a gastight vessel containing a cathode and an anode separated by a path of substantial distance, a gas in said vessel, magnetic means for producing a ux in said path, said magnetic flux being in a direction to increase the probability of ionization in said path, said gas during operation being maintained at a pressure sufciently low to prevent appreciable'ionization of the gas from occurring and an appreciable current from passing between said anode and cathode at applied voltages in excess of ionization voltages ofthe gas in absence of said magnetic iiux, said pressure being sufficiently high, however, to produce in the presence of said magnetic iiux copious ionization of said gas through said path at a voltage of the order of the ionization voltage of the gas or less.

10. A space discharge device comprising a gas'- tight vessel containing a cathode and an anode separated by a path of substantial distance, a gas in said vessel, magnetic means for producing a flux in said path, said magnetic ux being in a direction to concentrate the electron'fiow from said cathode to said anode along a restricted beam in said path, said gas during operation being maintained at a pressure sufficiently low to prevent appreciable ionization of the gas and conduction of current from .occurring between said anode and cathode at applied voltages in excess of ionization voltages of the gas in absence of said magnetic flux, said pressure being suiiiciently high, however, to produce in the presence of said magnetic flux copious ionization of said gas and conduction of current through said path at a voltage of the order of the ionization voltage of the gas or less.

11. A space discharge device comprising a gastight vessel containing a cathode and an anode separated by a path of substantial distance, said vessel having interior walls confining the discharge path, a gas in said vessel, and magnetic means for producing a flux in said path concentrating the electron flow along said confined path away from the walls, said gas during operation being maintained at a pressure sufciently low to prevent appreciable ionization of the gas from occurring and an appreciable currentfrom passing between said anode and cathode at applied voltages in excess of ionization voltages of the gas in absence of said magnetic ux, the transverse area of said conned path being sufficiently large and said pressure being sufiiciently high, however, to produce in the presence of said magnetic flux copious ionization of said gas through said path at a voltage of the order of the ionization voltage of its gas or less.

12. A space discharge device comprising a gastight vessel containing a cathode and an anode separated by a path of substantial distance, a gas in said vessel, means for producing a magnetic ux in said path and coaxial therewith, .means for producing a magnetic ux in said path and transverse thereto, said gas during operation being maintained at a pressure suiiciently high to produce in the presence of said coaxial magnetic iiux copious ionization of said gas and substantial conduction of current through said path, said pressure being suiliciently low, however, to decrease the conduction of current between cathode and anode at applied voltages in excess of the ionization voltage of the gas upon increase of said transverse magnetic flux with respect to said coaxial flux.

13. A space discharge device comprising a gastight vessel containing a cathode and an anode separated by a path of. substantial distaince, a gas in said vessel, a plurality of magnetic means for producing iiuxes in said path coaxialtherewith and transverse thereto, said magnetic means being variable to vary the relative magnitudes of said coaxial and transverse fluxes, said pressure being suiciently high to produce in the presence of a predominantly coaxial flux copious ionization and conduction of current through said path, said gas lpressure being suiciently low to cause substantial ionization and conduction of current between said cathode and anode to cease upon a decrease of said coaxial flux below a minimum value.

14. A space discharge device comprising a gastight vessel containing two electrode elements separated by a path of substantial distance, a gas in said vessel, means for causing a discharge to pass between said electrode elements, the pressure of said gas being sufficiently high to produce intense ionization upon the passage of saiddischarge,elec trically-conductive means positioned adjacent the discharge path between said electrode elements within said envelope,and means for impressing a magnetic field on the discharge space immediately adjacent said electrically-conductive means and transversely to said discharge path to force the path of the discharge over against said electrically-conductive means to control the discharge.

15. A space discharge device comprising al gastight vessel containing two electrode elements separated by a path of substantial distance, a gas in said vessel, means for causing a discharge to pass between said electrode elements, the pressure of said gas being sufllciently high to produce intense ionization upon the passage of said discharge, electrically-conductive means having an extended surface within said envelope surrounding at least in part the discharge path between said electrodes, and means for impressing a magnetic eld on the discharge space, at least in part surrounded by said electrically-conductive means and transversely to said discharge path to force the path of the discharge over against said surface of said electrically-conductive means to control the discharge.

16. A space discharge device comprising a gastight vessel containing two electrode elements separated by a path of substantial distance, a gas in said vessel, means for causing a discharge to pass between said electrodes, the pressure of said gas being suiliciently high to produce intense ionization upon the passage of said discharge, means adjacent the discharge path between said electrode element for receiving electrons from said discharge path, and means for impressing a magnetic eld transversely to the discharge path between said electrode elements in the vicinity of said electron-receiving means for controlling the discharge.

17. A space discharge device comprising a gastight Vessel containing a thermionic cathode and an anode separated by a path of substantial distance, magnetic means for producing a flux in said path and parallel thereto, and a gas in said vessel, said gas during operation being maintained at a pressure suiiiciently low to prevent gas through said path at a voltage ci the order ot the ionization ,voltage of the gas or less.

18. A space discharge device comprising a gastight vessel containing al thermionic cathode, and an anode separated by a path of substantial distance, said vessel having interior walls coniining the discharge path and adapted to receive electric charges having a controlling effect on theI space current, a gas in said vessel, and magnetic means for producing a flux in said path and parallel thereto concentrating the electron ow along said confined path away from the walls, said gas during operation being maintained at apressure sufficiently low to prevent appreciable ionization of the gas from occuring and an appreciable current from passing between said anode and cathode at applied voltages in excess of ionization voltages of the gas in absence oi said magnetic iiux, the transverse area ci said confined path being suiciently large and said pressure being sumciently high, however, to produce, in the presence of said magnetic ux, copious ionization of said gas through said path at a voltage of the order of the ionization voltage of the gasor less.

19. An electrical space discharge device including a plurality of elements comprising an anode element and a thermionic cathode, said anode element and cathode being spaced apart to provide a discharge path between them, an ionizable gas in said vessel, one of said elements having surfaces adjacent the paths of the electron ow in said discharge, and means for producing a magnetic eld in said path and substantially parallel with said path throughout substantially its entire length.

20. An electrical space discharge device including a plurality of elements comprising an anode element and a thermionic cathode, said anode element and cathode being spaced apart to provide a substantially straight-line discharge path between them, an ionizable gas in said vessel, one of said elements having surfaces adjacent the paths of the electron flow in said discharge, and means for producing a magnetic ield in said straight-line path and substantially parallel with said straight-line path throughout substantially its entire length.

21. An electrical space discharge device including a plurality of elements comprising an anode and a thermionic cathode, said anode and catharcane ode being'spaced apart to provide a space discharge path between them, an ionizable gassin said vessel, one o! said elements having surfaces adjacent the paths oi' the electron flow in-said dischargameans for producing an electric neld between said cathode and anode to produce a discharge in said path, and means for producing a magnetic tleld in said path and substantially` parallel with said electric ileldthroughout substantially -the entire discharge path.

22. A space discharge device comprising a gastight vessel containing a thermionic cathode and an anode separated by a substantial distance and adapted to support a discharge betweer'rthem in which electrons emitted from the cathode travel along a predetermined path to said anode, magnetic means for producing a flux in said electron path and parallel thereto throughout substantially the entire length oi' said electron path;` and a gas in said vessel, said gas during operation being maintained at a pressure sufficiently low to prevent appreciable ionization of the gas from occurring and an appreciable current from passing between said anode and cathode at applied voltages in excess of ionization voltages of the gas in absence of said magnetic ux, said pressure being sufficiently high, however, to produce, in the presence of said magnetic flux, copious ionization of said gas through said path.

23. A space discharge device comprising a gastight vessel containing a thermionic cathode, and an anode separated by a substantial distance and adapted to support a discharge between them in which electrons emitted from the cathode travel along a predetermined path to said anode, said vessel having interior walls conning the discharge path and adapted to receive electric charges having a controlling effect on the space current, a gas in said vesseLand magnetic means for producing a iiux in said electron path and parallel thereto throughout substantially the entire length of said electron path, said flux concentrating the electron flow along said coniined path away from the walls, said gas during operation being maintained at a pressure suiiciently low to prevent appreciable ionization of the gas from occurring and an appreciable current from passing between said anode and cathode at applied voltages in excess of ionization voltages of the gas in absence of said magnetic flux, the transverse area of said confined path being suillciently large and said pressure being sufficiently high, however, to produce, in the presence of said magnetic iiux, copious ionization of said gas through said path.

CHARLES G. SMITH.

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