US2124682A

US2124682A - Electrical gaseous discharge device

Info

Publication number: US2124682A
Application number: US612235A
Authority: US
Inventors: Percy L Spencer
Original assignee: Raytheon Manufacturing Co
Current assignee: Raytheon Co
Priority date: 1932-05-19
Filing date: 1932-05-19
Publication date: 1938-07-26
Anticipated expiration: 1955-07-26

Description

July 26, 1938. P. L. SPENCER 2,124,632

ELECTRICAL GASEOUS DISCHARGE DEVICE Filed May 19, 1952 2 Sheets-Sheet 1 uuuuunn E621.

mom/Er Patented July 26, I938 UNITED STATES PATENT OFFICE ELECTRICAL GASEOUS DISCHARGE DEVIC of Delaware Application May 19, 1932, Serial No. 612,235

28 Claims.

This invention relates to gaseous discharge devention will be best understood from the following description of exemplifications thereof, reference being had to the accompanying drawings, wherein:

Fig. 1 is a cross-sectional view of one embodiment of my invention showing a discharge device with one cathode and one anode, together with a diagrammatic representation of a circuit which may be used therewith;

Fig. 2 is a view similar to that of Fig. 1, showing a different form of discharge device having one cathode and two anodes;

Fig. 3 is a similar view showing a discharge device having two cathodes and one anode; and

Figs. 4, 5 and 6 are curves for analyzing the relationships between the current, voltage and magnetic variations.

In Fig. 1, i represents a hermetically-sealed glass envelope having an enlarged chamber 2 at one end thereof within which is supported a thermionic cathode 3 at the inner end of a reentrant stem 4. The cathode 3 is supported by two lead-in wires 5 and 6 which pass through and are sealed in the inner end of the reentrant stem 4. The cathode preferably comprises a metallic filament, such as, for example, nickel coated with some material to increase the electron emissivity of said filament. Such a coating may consist, J for example, of barium or strotium oxide. At the opposite side of the chamber 2 from the stem 4, the envelope I is formed to provide an elongated tubular section I. At the opposite end of this tubular section from the cathode 3, is provided a cooperating anode 8 supported at the inner end of a reentrant stem 9. The anode 8 is preferably supported by an anode lead I passing through and being sealed in the end of said stem 9. The "anode 8 is formed of some suitable refractory conducting material, such as, for example, graphite, carbon, tantalum, or carbonized nickel. Interposed between the cathode 3 and the anode 8 and surrounding the discharge path between them is provided a conductive tubular member Ii. The tubular member II is made of non-magnetic material, and preferably comprises a cylinder of thin sheet metal, such as, for example, tantalum. Member ll may be of any other suitable form, such as, for example, a wire mesh or a metallic deposit on the walls of the tubular section 1. Also it is possible to make it so that it does not completely surround the discharge path within it. The tubular member ll preferably fits snugly within the glass tubular section 1, whereby said tubular member II is supported by the walls of said tubular section I. A lead-in wire l2 also sealed through the end of the reentrant stem 9 and electrically connected to the tubular member ll aflords an external electrical connection to said member. In order to protect the inner end of the reentrant stem 4 against the energy generated by the discharge between the cathode and anode, there is provided a shield I3 supported by one of the cathode leads, such as, for example, 5. The other cathode lead 6 passes through an opening I4 in said shield. The envelope I after being thoroughly evacuated in accordance with the usual practice is provided with some suitable gaseous filling which may be, for example, a metallic vapor, such as mercury vapor. In order to supply this vapor, a small quantity of mercury 15 is introduced into the tube. Of course it is to be understood that any ionizable gas, such as, for example, one of the noble gases, may be used as the filling within the envelope I. Furthermore, any suitable mixture of gases and vapors may be utilized in the device. In order to supply power to the device, there may be provided a supply transformer l6 having a primary l1 and a secondary I 8. The filament 3 may be provided with heating current by a section I9 at one end of the secondary l8. The opposite end of the secondary 18 may be connected by means of a conductor 28 through any desired load device 2| to the anode lead Ill. The lead-in wire I2 for the tubular member II is connected through a resistance 22 to the anode lead-in l0. Resistance 22 is of comparatively .high value, for example, of the order of about one-half a megohm in order to limit the current to the member II to a negligible value. It will be seen that upon energization of the transformer IS, the filament 3 will be supplied with heating current, whereby it will be raised to a temperature at which it emits a copious supply of electrons. When the anode 8 becomes positive, these electrons will travel toward said anode, producing an intense ionization of the gas within the envelope, whereupon a current of large value will flow between the anode 8 and the cathode 3. I have discovered in such a device that if a magnetic field is applied transversely to the discharge path between the anode 8 and the cathode 3, no current will pass between these electrodes when the magnetic field atta'ms a comparatively low value This transverse magnetic field may be applied in any suitable manner. For example, in Fig. l, I have shown a magnet 23 external to the tube. adjacent the tubular member Ii, suitably positioned so that its field passes into the discharge space between the'cathode 3 and anode 8 transversely thereto. Since the value of the magnetic field at which the tube will not conduct is fairly critical, I prefer that the magnet 23 be biased, as, for example, by having it in the form of a permanent magnet, so that its normal field is slightly below the critical value at which the tube ceases to conduct. The magnet 23 could, of course, have an auxiliary winding (not shown) to bias it to the proper value of magnetization. In order to provide means for controlling the magnitude of the magnetic field, I provide a coil 24 wound around the magnet 23 and energized from some suitable source of current, such as, for example, a battery 25. The magnitude of the current through the coil 24 and consequently the magnetic field may be controlled by some suitable means, such as an adjustable resistance 28.

In the device as described above, I have found that when the magnetic field is below a certain minimum, current will fiow between the anode 8 and the cathode 3, whenever the anode 8 is positive, and therefore a rectified current will fiow through the load device 2|. As the magnitude of the field is increased by means of regulating the adjustable resistance 28, the amount of current flowing through the load device 2i gradually decreases in value until when a certain maximum field is reached the tube is entirely non-conducting and substantially no resultant current flows through said load device.

According to my present understanding of the theory of operation of the device, it operates as follows. When the anode 8 and tubular member H become positive, a small space current fiows between the cathode 3 and the end of the tubular member ll adjacent said cathode. This current may ordinarily be of the order of about one-tenth of a milliampere. Inasmuch as these tubes are designed to handle currents of the order of amperes, this space current is so small as to be practically negligible insofar as the load device is concerned. However, this small amount of current makes a comparatively large number of ions in the region between the cathode 3 and the end of the tubular member H.- The member ll being of conductive material forms an electrostatic shield around the space within it. Thus the intensity of the electrostatic field, due to the -negative charge on the cathode, decreases very rapidly as we go down the tubular member l| toward the anode. Likewise the electrostatic field, due to the positive charge on the anode, decreases very rapidly as we go up the tubular member i I toward the cathode. With ordinary values of voltage, a portion within the tubular member intermediate the anode and cathode can be said to be substantially electrostatically field free. Under these conditions the intensity oi ionization decreases very rapidly as we go down the tubular member from the cathode toward the anode 8. There are a very few of the electrons existing within the tubular member ll, however, which come under the influence of the positive charge on the anode 8. As the voltage on the anode becomes greater, its positive charge increases. As the positive charge on the anode increases, its electrostatic field will increase in intensity inside of the tubular member H, and a larger number of electrons will come under its influence. If enough of these electrons come under the influence of this charge, cumulative ionization results and the full current flows. Cumulative ionization may be explained as follows. An electron coming under the influence of the charge or field of the anode 8 is accelerated toward the anode, and may acquire. sufilcient energy to ionize an atom of gas upon collision therewith, whereupon it is again accelerated to ward the anode. There is, however, some difiusion to the walls of the tubular member ll of electrons, whether coming from the cathode 3 or being liberated as the result of the ionization of gas atoms. The electrons reaching the walls of. member ll fiow out of the tube through the lead wire i2, and are thus removed or lost from the discharge path between the cathode and the anode. If the rate at which electrons are lost to the member II is greater than the rate at which electrons are liberated as a result of the ionization of gas atoms, cumulative ionization cannot occur and the discharge does not start. If, however, the rate at which electrons are so lost is less than the rate at which electrons are liberated, cumulative ionization does occur and the discharge starts. Upon the starting of a discharge the intensity of ionization along the entire discharge path increases enormously, and a large current flows between the cathode and anode. In absence of a transverse magnetic field, the rate of loss of electrons in the device as shown is ordinarily less than that which will prevent cumulative ionization, and the discharge will start very soon after the beginning of each half of the alternating current cycle when anode 8 becomes positive. When the transverse magnetic field, due to the magnet 23, is impressed on the device, this field acts upon electrons which come within the tubular member and which otherwise might proceed toward the anode 8 to push them over against the walls of the tubular member II, and thus increases the rate at which the loss of these electrons to the member ll occurs. It will be seen that the ease with which the electrons are controlled by the magnetic field is particularly great in the electrostatically field-free space referred to above. The pushing of the electrons overagainst the walls of the tubular member ll moves the entire region of more intense ionization over against these walls, and thus an electron cannot undergo many ionizing collisions before it is captured by the wall of member ll. Also the electrons liberated as a result of. such ionizing collisions are liberated close to the walls of member II, and are also soon captured by it, all of which greatly increases the rate of the loss of electrons to the member I I. This rate of loss increases with the magnitude of the magnetic field. Thus with each definite value of voltage, when the field becomes strong enough, the rate of loss of electrons becomes so great that cumulative ionization is impossible, and therefore the discharge will not start. However, any lesser value of field does not produce a sufiicient loss of electrons to prevent cumulative ionization, and consequentiy the discharge starts between cathode 3 and anode 8. The control of. ionization'which is aiforded by such a magnetic field may be termed a control of the propagation of ionization along the discharge path between the cathode and anode. As soon as the discharge begins, the enormous increase in ionization referred to above occurs and a large current flows between the cathode and anode. Since the intensity of ionization and consequently the rate at which electrons are liberated increases so enormously, a magnetic field which may be sufficiently large to prevent the start of a discharge will ordinarily be unable to increase the rate of electron loss to a sufllcient degree to stop the discharge after it has once started.

It should be noted that although the above analysis refers to the loss electrons to the walls of member H, the same eflect exists al- ,though to a lesser degree with respect to positive ions within the space surrounded by the tubular member. These ions are not only captured by the walls of member II by diflusion thereto, but are also acted upon by the magnetic field to tend to push them over against the walls .of member II. The removal of positive ions from the discharge path removes additional current carriers, and therefore decreases the tendency of a discharge to start. Therefore, it is to be understood that whenever I refer to the loss of electrons to the walls oi member II, I also mean that the same thing to a lesser degree is occurring to positive ions. The manner in which the magnetic field controls the magnitude of the current fiowing through the load device 2| may be seen more clearly by referring to Fig. 4. In this figure, curve a represents the variation of voltage applied between the cathode 3 and the anode 8 with respect to time. Since we can assume. for the purposes of analysis that the load It is a resistance load, each point on this curve can represent the amount of current which would 5 flow through the circuit if the device were conducting at that point. When the field, due to the magnet 23 and the electromagnetic coil 24, is below a certain minimum, the device as stated above becomes conducting whenever the anode 8 is positive. Thus, the device is conductive between the points I; and c of a single voltage and current cycle during which time the anode 8 is positive, and is non-conductive between points 0 and (1 during which the anode 8 is negative. Although in each of my curves I have shown the discharge starting at zero voltage and stopping at zero voltage, actually the voltage must rise to a small starting value before the discharge will start, and will fall to a value just below the tube drop voltage when the discharge will stop. Since in comparison with the operating voltages, these values are quite small, they may be considered as zero at least for purposes of illustration. As the value of the magnetic field is increased by a certain amount, the rate of loss of electrons becomes so great that suflicient electrons to produce cumulative ionization do not come under the influence of the field on anode 8 until the voltage on the anode reaches the point e on curve a, and thus the tube will not "become conductive until the voltage between the Y anode and cathode reaches this point. Under these conditions, the tube will only conduct between the point 1, at which the voltage reaches 65 the value e, and the point e at the end of that half of the voltage cycle. As the magnetic field is further increased by a certain amount, the rate of loss of electrons becomes still greater so that the tube does not start to become conductive until the voltage between the anode and the catl'rode reaches a value of g on the voltage curve n. Thus the tube only conducts from the point h, at which the voltage attains the value g, and the point e at the end of that half of the voltage cycle. The field may be further increased until finally the tube does not become conductive until the voltage between the anode' and the cathode reaches its maximum value i. Thusthe tube only is conductive through a quarter of a complete voltage cycle, namely, from the point i at which the voltage reaches its maximum value and -the point e at the end of said half of the voltage cycle. If the magnetic field is increased beyond this point, the tube can never become conductive inasmuch as it would require a voltage greater than the peak value of the voltage between the anode and cathode to start the discharge. It can be seen that when the tube is conductive only during a portion of the positive half of the voltage cycle, the

resultant value of current flowing through the load device becomes less as the portion 01' said positive half of the voltage cycle during which the current fiows becomes less. Since, as shown above, the magnitude of the magnetic field determines the portion of the voltage cycle during which the tube is conductive, by controlling the magnitude of the magnetic field we can con- :Iige the amount of current flowing through the The provision of the tubular member ll between the cathode and anode performs various important functions. If we were to attempt to control the current between the cathode and anode by a transverse magnetic field without the provision of such an element as the tubular member II, we could obtain some increase in the loss of ions created in the space between the cathode and anode by forcing electrons over against the glass walls of the tube by means of said transverse magnetic field. These electrons upon reaching the walls of the tube would charge it negatively. This charge, however, can only be removed by the neutralization thereof by positive ions created within the discharge space. Since these positive ions are relatively heavy and. diffuse somewhat slowly, the negative charge upon the walls of the tube becomes fairly large and repels any additional electrons which may be forced over against the walls of the tube by the magnetic field. Thus the rate at which electrons can be withdrawn from the discharge path is much less in such a device than with the provision of a conductive tubular member surrounding the discharge space. ber H is conductive and is connected to lead the electrons and positive ions which it captures out of the tube, the rate at which these current carriers can be removed from the path of the discharge is greatly increased. This efiect can be obtained to some degree even if ,the member.

ll does not completely surround the discharge path, as shown, and consists merely of a conductive member of extended area placed adjacent the discharge path. Further, in the absence of such a conductive tubular member, as H, the electrostatic field from the anode 8 can act freely across the whole space, and thus exert a very strong influence upon the electrons throughout this entire space. However, the tubular member ll acts as an electrostatic shield so that the field of the anode 8 can extend effectively only a short distance within said tubular member I l. Therefore, the loss of electrons by being forced over against the walls of the tubular member may be small enough so that there is a considerable number of free electrons left within the tubular member ll, yet due to the electrostatic shielding of this member, the field of the anode 8 is not strong enough to influence these Since the memof two and one-half inches.

electrons to any considerable desree. Under these conditions, these considerable number of electrons may exist within the tubular member ii, and yet cumulative ionization will not occur. This effect likewise exists even though the member Ii does not completely surround the vdischarge space. As long as the member Ii accomplishes some electrostatic shielding of the discharge path, the above advantage exists in some degree. Thus the control of the discharge by a transverse magnetic field becomes a comparatively simple matter by the provision of the conductive tubular member H while it is a matter of considerable difficulty without such a member. In one of the tubes which I have constructed in accordance with the above disclosure,

I used a tubular member ii having a diameter of one and one-quarter inches and a length In this tube, when 110 volts of alternating current are applied between the cathode 3 and anode 8, current flowed freely. However, when a transverse magnetic field of about thirty gauss was applied, the current ceased. Merely a change in this transverse magnetic field of about three gauss was sufllcient to change the tube from a conducting to a nonconducting state. This tube operated satisfactorily with a filling of mercury vapor at pressure broadly between .001 mm. and .01 mm. of mercury. If it is desired to use higher pressure within the tube, the tubular member II should be made longer or of smaller diameter or both. The pressure in the tube can be controlled by properly proportioning the external area of the glass envelope or by providing additional condensing chambers removed from the path of the discharge. Tubes have been constructed in which variations of about one-quarter of a watt have been sufllcient to control two kilowatts of power directly.

Instead of having a tube with but a single cathode and a single anode, it is often desirable to construct such a device having two anodes cooperating with the cathode. Such an arrangement is shown in Fig. 2. In this figure a hermetically sealed envelope 21 encloses a thermionic cathode 28 similar to the cathode 3 in Fig. 1 and similarly supported within an enlarged chamber 29. -The envelope 2'! is provided with two elongated tubular sections 30 extending from opposite sides of the chamber 29. At the oppos te end of each of these tubular sections is an anode 3i cooperating with the cathode 28. Each of these anodes is similar to the anode 8 in Fig. 1, and is similarly supported. Interposed between each of the anodes 3i and the cathode 28 within each of the tubular sections III is a tubular member 82 similar to the tubular member ii, as shown in Fig. 1, and likewise similarly supported. The tubular members may extend up around the anodes 3i if it is desired to shield the discharge paths adjacent the anodes from charges on the glass walls of the tube. Such an arrangement, however, is not necessary, the arrangement in Fig. 1 being equally as satisfactory. The interior of the envelope 2'! is provided with a, suitable gas filling, as set forth for Fig. 1, which filling may be a vapor supplied, for example, from a quantity of mercury 33 within the envelope 21. are connected to its corresponding anode 3i through resistance 34 corresponding to the resistance 22 in Fig. 1.

The device in Fig. 21s supplied with a power from a supply transformer 35 having a primary Each of the tubular members 32 3| and a secondary 31, the opposite ends of which are connected to the anode leads 88, each connected to its respective anode 8|, The cathode 28 is supplied with heating current from a heating transformer 88 having a primary 48 and a secondary 4i, which secondary is connected at opposite ends to the two cathode leads 42 and 43. A point intermediate the ends of the secondary 31, which is preferably the mid-point thereof, is connected through some suitable load device 44 to the cathode 28. This connection may be completed, for example, by a connector leading to a point intermediate the ends of the secondary 4i, which point is preferably at the center of said secondary. It will be seen that upon energization of the transformers 35 and 38, current will flow during alternate half cycles between the cathode 28 and one and the other of the two anodes 8i. As a result, a rectified current will fiow through the load device 44. Instead of but a half cycle of the alternating voltage wave being utilized, as is the case in Fig. 1, both halves of the alternating voltage cycle are rectified, producing a more uniform fiow of current through the load device. In order to control the fiow of current between each of the anodes 3i and the cathode 28, I have provided two magnets 45 each similar to the magnet 28 in Fig. 1, and each also provided with a control coil 46 similar to the control coil 24 in Fig. 1. Each of the control coils 46 may be energized by a controlled direct current, as is the case in Fig. 1, whereupon the current between each of the anodes 2i and the cathode 28 is controlled as explained for Fig. 1. If, however is is desired to utilize alternating current for the energization of each of the coils 46, this may be accomplished, for example, by means of such a circuit as is shown in Fig. 2. In this arrangement, the two coils 46 are connected in series across the two terminals of the secondary 31. In this series connection are placed one or more condensers 41 of a value to make this series circuit substantially resonant to the frequency of the applied voltage. Thus the current flowing through the coils 46 and consequently the variation in the magnetic field will be substantially in phase with the voltage applied between each of the anodes 3i and the cathode 28. However, I wind my coils 46 in such a direction that the variation in magnetic field takes place in the opposite direction to the variation in voltage between the corresponding anode and the cathode. I also bias the initial and average magnetization of each of the magnets 45 to a certain definite value, either by providing auxiliary permanent magnets (not shown) or additional energizing coils 48 fed by direct current from a battery 49, and cooperating with each of the magnets 45. To prevent the oils 46 from inducing excessive currents in coils 48, I provide a choke 48' in series with the coils 48. In order to control the magnitude of the current through each of the coils 46 and the consequent magnitude of magnetic variation, I provide an adjustable resistance 58 in the above-mentioned series circuit. The manner in which the resultant variation in the magnetic fields of each of the magnets controls the magnitude of the discharge in the tube, can be best understood by referring to Fig. 5. In Fig. 5 curve It represents the variation in voltage applied between one of the anodes 3i and the cathode 28, and as with Fig. 1, assuming that the load 44 is a resistanceload for the purpose of analysis, each point on this curve can represent the amount of current which would fiow from the load if thedevice were conducting at that point. The voltage between the other anode and the cathode is, of course, out of phase with the voltages represented by curve It. At some value of magnetic field, which may be represented by the line I, the loss of electrons to the corresponding tubular member 32 decreases to such a point that the discharge is able to start. Under such conditions, each of the magnets 45 is biased so that its initial and average value of magnetization, which may be represented by the line 111., is greater than the value represented by I. At some setting of the adjustable resistance 5|), the variation in magnetic field due to the variation in the coil 46 follows the curve 11. It will be seen that with this variation of the magnetic field, the value 1 is reached when the voltage curve 76 has progressed through a quarter of its entire cycle. The discharge path between the corresponding anode 3| and the cathode thus becomes conducting at this point, which may be represented at o, and the discharge continues to the point p at the endof that half of the voltage cycle. If the resistance 50 is adjusted so as to decrease the current through the coil 46 and the consequent decrease in the magnitude of the variation of the magnetic field, it will be seen that the magnetic field never decreases to the value I, and therefore the discharge will not start between the corresponding cathode and anode. If, however, the resistance 50 is adjusted so as to increase the current through the coil 46, and consequently the magnitude of the magnetic variation, the field of the magnet 45 will follow some such curve as may be represented by q. Under these conditions the magnetic field will reach the value I sooner in the voltage cycle 16 than before. Thus the discharge path between the corresponding anode and cathode will become conductive at the point r at which the magnetic variation q reaches the value I, and this discharge path will continue to be conductive from said point r to the point p at the end of that half of the voltage cycle. As the value of the current through 46 increases as a result of the adjustment of the resistance 50, the corresponding discharge path will become conductive sooner during the voltage cycle. Thus, as explained for Fig. 4, the resultant value of current through the respective discharge path can be controlled by controlling the adjustable re sistance 50. The analysis applies with equal force to the discharge path between theopposite anode and the cathode, except that each of the variations is displaced exactly 180 from that as shown in Fig. 5. Thus each half of the voltage cycle is directed through the load device 44 in the same direction, and is controlled as explained above.

Instead of utilizing two anodes with a single cathode, it may be desirable to utilize a tube having two cathodes cooperating with a single anode. 3. In this figure a hermetically sealed envelope 5| encloses two thermionic cathodes 52 at each end thereof. Each of these cathodes is contained within an enlarged chamber 53, and is supported at the inner end of a reentrant stem 54. Although these cathodes. may be of the filamentary type, as disclosed in Figs. 1 and 2, yet in some instances I prefer to use an indirectly heated type of cathode inasmuch as such acathode can be operated more efficiently and with Such an arrangement is shown in Fig.

a greater electron emission. Each of the oathodes 52 consists of a hollow member 53' closed at one end and carrying a series of radial fins 54' on the outside. thereof. Both the fins and the external surface of the member 53 are preferably covered with a material to increase'their electron emissivity, which material may be, for

example, the oxides of alkali earth metals. In order to heat the electron emitting surfaces to their emitting temperature, a heating filament 55 is provided within the hollow member 53'. This heating filament is supported within said hollow member by means of filament leads 56 and 51 sealted through the end of the reentrant stem 54. In order to prevent undue radiation of heat from the electron-emitting surfaces and. thus maintain them more efliciently at their emitting temperature, a metallic heat shield 58 is provided which surrounds hollow member 53' and its fins 54', and is mechanically connected to said hollow member at one end thereof. The entire cathode structure may be supported by two wires 59 and 60 also sealed in the end of the reentrant stem 54, one of which wires, for example so, may extend through the end of said reentrant stem and form an external electrical connection .for the cathode. Intermediate the ends of the envelope 5| at substantially the center point of a tubular section 6| thereof, I provide a single anode 62. This anode is made of some suitable refractory conducting material, such, for example, as specified for the anodes in Figs. 1 and 2. The anode 62 is supported at the inner end of a reentrant stem 63 by means of an anode lead 64 sealed in the end of said...

stem. Interposed between each of the cathodes and the opposite faces of the anode 62 are tubular members 65 similar to the tubular members II and 32 in Figs. 1 and 2.- These tubular members 65 are supported within the tubular section 6| substantially as are the tubular members referred to in Figs. 1 and 2. Each of the tubular members 65 is provided with a lead 66 sealed in the end of the reentrant stem 63, and affording an external electrical connection for each of said tubular members. It is desirable to prevent electrons and positive ions from passing from the discharge space on one side of the anode to the discharge space on the opposite side thereof. If this is not done, ions created in one discharge path pass into the other discharge path, and a considerable number of ions exist near the anode at the start of the active cycle in said other discharge path. The presence of these ions increases the tendency of the discharge to start, and renders the control by the magnetic field more difficult. In order to prevent this drawback, the ends of the tubular members 65 adjacent the anode 62 are brought fairly close to the surface thereof at a distance so that passage of electrons or positive ions from one side of the anode to the other is substantially prevented. In order that this passage of electrons and positive ions be more completely prevented, the anode 82 is preferably made somewhat larger than the inner diameter of each of the tubular members 65 so as to effectively shield the discharge path on one side of said anode to the discharge path on the opposite side thereof. The interior of the envelope 5| is provided with suitable gas filling, such as set forth for Figs. 1 and 2. Each of the tubular members 65 is connected to the anode through a resistance 12 corresponding to the

resistances

22 and 34 in Figs. 1 and 2.

' the secondary 63.

In order to supply the device in Fig. 3 with power, I have provided a power transformer 'I having a primary 68 and a secondary it. .Each of the heating filaments BI is supplied with heating current from sections 10 at opposite ends of The cathode-emitting surfaces may be connected to opposite ends of the secondary 68, for example, by having the oathode lead 60 electrically connected to one 01 the heating filament leads 51. A point intermediate the ends of the secondary 88, which is preferably the mid-point thereof, is connected through some suitable load device H to the anode lead 64. It will be seen that upon energization of the transformer 61, current will flow during alternate half cycles between the anode 62 and \one or the other of the cathodes 52, whereupona rectified current will flow through the load device H. In order to control the flow of current between each of the cathodes 52 and the anode 62, I have provided two magnets 13 similar to the magnets 45 in Fig. 2. Each of these magnets is provided with a control coil Hi similar to the coils in Fig. 2. The magnetization of each of the magnets may be controlled in any desired manner, for example, either' by such an arrangement as shown in Fig. 1 or such a one as shown in Fig. 2. -'However, it may be desired to utilize a still diflerent mode of control for these magnets, and an example of a still further control arrangement is illustrated in Fig. 3. The two coils II are connected in seriesacross the two terminals of the secondary 69. In this series connection are placed one or more condensers 15, the total value of which is much smaller than that needed for resonance. As a result, the current through the coil H and .consequently the variation in the magnetic fields of each of the magnets I3 leads the voltage applied between each of the cathodes 52 and the anode 62. In series with the coil 14 and the condensers I5 is placed an adjustable resistance 16. By adjusting the'resistance 16, the angle between the current through the coils I4 and the voltage applied between the cathodes and the anode is changed. By referring to Flg.-6, we can see how this relationship between the magnetic field and the applied voltage controls the current through the tube. In Fig. 6, curve 8 represents the variation in voltage applied between one of the oathodes 52 and the anode 62, and as stated for Figs. 4 and 5 may also represent at each point the value of current which would fiow through the load device ii if the tube were conducting at that point. Curve t represents the current fiowing through the coil I4, leading the curve s by a certain angle which may be called 0. Curve t thus also represents the variation in the magnetic field oi' each of the magnets 13. It should be noted atthis point that these magnets 13 may be biased as suggested for the magnets in Fig. 2, although it is possible to secure sufflcient variation in the fields of these magnets 13 without any biasing. The various constants of the magnet 13 may be so chosen that whenever the curve t, as shown in Fig. 6, is at a slightpositive value, the magnetic field of the magnet 13 is sufllciently large so that a discharge cannot start between the corresponding cathode and anode. Thus we see that when the current through coil 14 fol- 1 lows the curve t, the magnetic field is sufficiently strong during the initial portion of the voltage cycle 8 so as to prevent a discharge from starting. It is not until the curve t passes the point it that the corresponding discharge path becomes conducting. Consequently the discharge between the corresponding cathode and anode will only be conducting between the point a and the point 1: at the end of the voltage cycle a. Thus this discharge path conducts only but a portion of the positive half of the voltage cycle. If, however, 0 is decreased by increasing the resistance r, the point u will more closely approach the point 1: and the period of a voltagev cycle during which the corresponding discharge path is conducting will be decreased. Consequently the resultant amount of current which flows through this discharge path is decreased. Likewise if 0 is increased by decreasing the value of the resistance 16, the resultant current through the corresponding discharge path will be increased. Instead of theparticular phase-shifting device illustrated, any suitable phase-shifting device may be employed for changing the phase angle between the applied voltage s and the current t through the coil I4. If desired, 'a phaseshifting device may be employed which will enable the operator to shift the phase of t through 180. Thus the current between the cathode and the anode could be made to start at any point in the positive half of the applied voltage 3. The above analysis applies with equal force to the discharge space between the other anode and the cathode, except that the curves applying to that discharge space are 180 displaced from those shown in Fig. 6. Thus, as explained for Fig. 2, the current due to each half of the voltage cycle is directed through the load device II in the same direction, and the magnitude of this current is controlled by the variation of the magnetic fields of the magnets 13.

I have found in each of the devices which I have described that it is'ordinarily difilcult to control the discharge by means of the transverse magnetic field if the load device contains a considerable amount of inductance. I have further discovered, however, that this difilculty may be entirely eliminated by placing a bypass resistance around the discharge path so that a small amount of alternating current may initially pass through the inductance of the load device. The value of this shunting resistance may be sumciently high so that the amount of current so flowing is negligible with respect to the total loadcurrent. In Fig. 3 I have shown such shunting resistances at 11 and 18, each of said resistances being in parallel with the discharge path between one of the cathodes and the anode. With a tube having dimensions, such as I have referred to above, and having 110 volts A. C. impressed between each cathode and the anode, each of the resistances I1 and 18 were about 500 ohms. With such an arrangement, an inductive load of considerable amperage was readily controlled. Of course it is to be understood that wherever I have quoted particular dimensions and figures, such are for the purpose of illustration only and are not to be construed in any limiting sense inasmuch as these particular values will be different in each application of my device and can have a very' wide range of values. Other arrangements for controlling an inductive load could be used, such as, for example, bypassing oi the load itself with a capacity in order to reduce the resultant alternating current impedance.

I wish it to be understood that the various control systems, as shown in Figs. 1. 2 and 3, can

be used interchangeably in each of the devices as shown in any of said figures. In addition, any other suitable control circuit may be utilized.

For example, the tubular member ll instead of being connected to anode 8 merely through a resistance could be left entirely free. With such an arrangement, the electrons forced over to the member ii would charge it negatively and thus attract positive ions which would neutralize the negative charge. In this manner the removal of electrons and positive ions from the discharge path can be accomplished, although the effect may be less than if the resistance 22 were provided. However, theabove arrangement still produces the fieldrec space together with its various advantages as well as other factors which result in the fact that the discharge in such a device can also be easily controlled by the transverse magnetic field. Also the tubular member I I could be biased with respect to the anode 8 by any suitable source of voltage. These and various other circuit connections will readily suggest themselves to those skilled in the art. Any other desired arrangement of electrodes can-also be utilized, it being merely necessary to provide at least two electrodes adapted to have an electrical discharge between them to which discharge path my novel control may be applied.

The invention is not limited to the particular details of construction, materials, quantities and values, or processes as described above, as many equivalents will suggest themselves to those skilled in the art. It is accordingly desired that the appended claims be given a broad interpretation commensurate with the scope of the invention within the art.

What is claimed is:

1. A space discharge device comprising a hermetically sealed envelope enclosing two electrodes in an ionizable atmosphere, said electrodes adapted to support a discharge between them, the pressure of said atmosphere b'eing sufliciently high to produce intense ionization upon the passage of said discharge, said envelope being provided with a tubular section surrounding a portion of the discharge path between said electrodes, a hollow tubular electrically-conductive member positioned within said tubular section, the transverse cross-section of said tubular member being substantially equal in size and shape with the inside transverse cross-section of said tubular section, whereby the outer wall of said tubular member lies closely adjacent the inner wall of said tubular section, and means for impressing a magnetic field on the discharge space within said hollow tubular electrically-conductive member and transversely to said discharge path within said hollow member.

2. A space discharge device comprising a hermetically sealed envelope enclosing a thermionic cathode, two anodes cooperating with said cathode and adapted to support a discharge with said cathode, an ionizable atmosphere in said envelope at a pressure sufliciently high to produce intense ionization upon the passage of said discharge, a separate electrically-conductive member having an extended surface within said envelope surrounding the discharge path between each anode and said cathode, and means for impressing a magnetic field on each of the discharge paths surrounded by said electrically-conductive members and transversely to said discharge path.

3. A space discharge device comprising a hermetically sealed envelope enclosing an anode,

two thermionic cathodes cooperating with said anode and adapted to support a discharge withintense ionization upon the passage of said discharge, a separate electrically conductive mom- I ber having an extended surface within said ensurface within said envelope adjacent the discharge path between said electrodes, means for impressing between said electrodes an alternating potential, means for impressing on said discharge space transversely to said discharge path a magnetic field varying in magnitude at the same frequency asthe voltage applied between said electrodes and out of phase with said applied voltage, and means for varying the phase angle between said applied voltage and said magnetic field.

5. In combination, a space discharge device comprising a hermetically sealed envelope enclosing two electrodes'in an ionizable atmosphere, said electrodes adapted to support a discharge between them, the pressure of said atmosphere being sufiiciently high to produce intense ionization upon the passage of said discharge, an electrically conductive member having an extended surface within said envelope adjacent the discharge path between said electrodes, means for impressing between said electrodes an alternating potential, means for impressing on said discharge space transversely to said discharge path a magnetic field varying in magnitude at.

the same frequency as the voltage applied between said electrodes and opposite to said applied voltage in time phase, means for biasing said magnetic field so that'its average value is greater than that which will allow a dischargeto. start between said electrodes, the variations in said field being such that the minimum values of said field are less than that value which will allow a discharge to start between said electrodes, and means for controlling the magnitude of said variations.

6. In combination, a space discharge device comprising a sealed envelope enclosing two electrodes in an ionizable atmosphere, said'electrodes,

tential cycle and to be greater than said value during the other half of said cycle.

'7. In combination, a space discharge device comprising a sealed envelope enclosing two electrodes in an ionizable atmosphere, said electrodes adapted to have impressed thereon an alternating potential and adapted to support a disl5 trically conductive member having an extended I charge between them, the pressure of said atmosphere being suiiiciently high to produce intense ionization upon the passage of said discharge, a member surrounding the discharge path between said electrodes, means for impressing on the discharge space within said member and transversely to said discharge path a varying magnetic field, means for causing the magnetic field to drop below the minimum value which will prevent a discharge from starting between said electrodes during one-half of the alternating potential cycle and to be greater than said value during the other half of said cycle, and means for varying the time at which the magnetic field passes through said value.

8. A space discharge device comprising an envelope enclosing two electrodes in an ionizable atmosphere, said electrodes adapted to support a discharge between them, means for controlling the propagation of ionization along the discharge path between said electrodes, comprising means for creating in the discharge path between said electrodes an unobstructed substantially field-free space freely exposed to access by the electrons emitted from said cathode during the absence of said discharge, and means for impressing a magnetic field transverse to the discharge path between said electrodes in said substantially field-free space, the pressure of said atmosphere being sufiiciently high to produce substantial ionization upon the starting of said discharge and to cause said discharge to continue in the presence of said. transverse magnetic field.

9. A space discharge device comprising an envelope enclosing two'electrodes in an ionizable atmosphere, said electrodes adapted to support a discharge between them, means for creating in the discharge path between said electrodes an unobstructed substantially field-free space freely exposed to access by the electrons emitted from said cathode during the absence of said discharge comprising a control unit interposed between said electrodes, said control unit having a conductive surface positioned adjacent the discharge path between said electrodes, and means for impressing a magnetic field transverse to the discharge path between said electrodes in said substantially field-free space, the pressure of said atmosphere being sufilciently high to produce substantial ionization upon the starting of said discharge and to cause said discharge to continue in the presence of said transverse magnetic field.

10. A space discharge device comprising an envelope enclosing two electrodes in an ionizable atmosphere, said electrodes adapted to support a discharge between them, a control unit interposed between said electrodes, said control unit having a conductive surface positioned adjacent the discharge path between said electrodes, said surface being freely exposed to access by the electrons emitted from said cathode during the absence of said discharge, and means for impressing a magnetic field transverse to the discharge path between said electrodes adjacent said surface, the pressure of said atmosphere being sufliciently high to produce substantial ionization upon the starting of said discharge and to cause said discharge to continue in the presence of said transverse magnetic field.

11. A space discharge device comprising an envelope enclosing two electrodes in an ionizable atmosphere, said electrodes adapted to support a discharge between them, a control unit interposed between said electrodes comprising an electrically-conductive member having an extended surface within said envelope surrounding at least in part the discharge path between said electrodes, said surface being freely exposed to access by the electrons emitted from said cathode during the absence of said discharge-and means for impressing a magnetic field transverse to the discharge path between said electrodes adjacent said surface, the pressure of said atmosphere being sufiiciently high to produce substantial ionization upon the starting of said discharge and to cause said discharge to continue in the presence of said transverse magnetic field.

12. A space discharge device comprising an envelope enclosing two electrodes in an ionizable atmosphere, said electrodes adapted to support a discharge between them, a control unit interposed between said electrodes comprising an electrically-conductive member having an extended surface within said envelope surrounding the discharge path between said electrodes, said surface being freely exposed to access by the electrons emitted from said cathode during the absence of said discharge, and means for impressing a magnetic field transverse to the discharge path within said conductive member, the pres sure of said atmosphere being sufficiently high to produce substantial ionization upon the starting of said discharge and to cause said discharge to continue in the presence of said transverse magnetic field.

13. A space discharge device comprising an envelope enclosing a thermionic cathode and an anode in an ionizable atmosphere, said electrodes adapted to support a discharge between them, means for controlling the propagation of ionization along the discharge path between said electrodes comprising means for creating in the discharge path between said electrodes an unobstructed substantially field-free space freely exposed to access by the electrons emitted from said cathode during the absence of said discharge, and means for impressing a magnetic field transverse to the discharge path between said electrodes in said substantially field-free space, the pressure of said atmosphere being sufliciently high to produce substantial ionization upon the starting of said discharge and to cause said discharge to continue in the presence of said transverse magnetic'field.

14. A space discharge device comprising an envelope enclosing a thermionic cathode and an anode in an ionizable atmosphere, said electrodes adapted to support a discharge between them, a control unit interposed between said electrodes, said control unit having a conductive surface positioned adjacent the discharge path between said electrodes, said surface being freely exposed to access by the electrons emitted from said cathode during the absence of said discharge, and means for impressing a magnetic field transverse to the discharge path between said electrodes adjacent said surface, the pressure of said atmosphere being sufficiently high to produce substantial ionization upon the starting of said discharge and to cause said discharge to continue in the presence of said transverse magnetic field.

15. In combination, a space discharge device comprising an envelope enclosing two electrodes in an ionizable atmosphere, said electrodes adapted to support a discharge between them, the pressure of said atmosphere being sufiiciently high to produce substantial ionization upon the charge path between said electrodes adjacent said surface, an electrical connection between said control unit surface and one of said electrodes, and means for limiting the amount of current fiow in said electrical connection to a negligible amount as compared with the normal load current fiowing between said cathode and anode.

16. In combination, a space discharge device comprising an envelope enclosing two electrodes in an ionizable atmosphere, said electrodes adapted to support a discharge between them, the pressure of said atmosphere being sufiiciently high to produce substantial ionization upon the passage of said discharge, a control unit interposed between said electrodes, said control unit having a conductive surface positioned adja-' cent the discharge path between said electrodes, said surface being freely'exposed to access by the electrons emitted from said cathode during the absence of said discharge, and means for impressing a magnetic field transverse to the discharge path.between said electrodes adjacent said surface, an electrical connection between said control unit surface and one of said electrodes, said connection containing a currentlimiting impedance.

17. In combination, a space discharge device comprising an envelope enclosing two electrodes in an ionizable atmosphere, said electrodes adapted to support a discharge between them, a control unit interposed between said electrodes, said control unit having a conductive surface positioned adjacent the discharge path between said electrodes, said surface being freely exposed to access by the electrons emitted from said cathode during the absence of said discharge, and means for impressing a magnetic field transverse to the discharge path between said electrodes adjacent said surface, and means for controlling the magnitude of said magnetic field, the pressure of said atmosphere being sufiiciently high to produce substantial ionization upon the starting of said discharge and to cause said discharge to continue in the presence of said transverse magnetic field.

18. In a space discharge device comprising an envelope enclosing two electrodes in an ionizable atmosphere, said electrodes adapted to support a discharge between them, the pressure of said atmosphere being sumciently high to produce substantial ionization upon the passage of said discharge, means for controlling the propaga-- tion of ionization along the discharge path between said electrodes comprising means for creating in the discharge path between said electrodes an unobstructed substantially field-free space, the method of operating said space discharge device which comprises impressing between said electrodes a voltage suflicient to initiate and sustain an ionizing discharge between said electrodes in absence of a transverse magnetic field, impressing upon said substantially field-free space a magnetic field transverse to said discharge path therein of suflicient magnitude to prevent said discharge from starting, and then lowering the intensity of the magnetic field transverse to said discharge path to such a value that said discharge starts under the application of said voltage to said electrodes.

19. In combination, an electron discharge device comprising an envelope containing a cathode, an anode, and an electron-deflecting chamber positioned between the cathode and anode, said chamber having a discharge opening, a source of electromotive force connected between the cathode and anode, an ionizable medium in said envelope, means mounted exteriorly of the envelope for causing the electrons in the defiection' chamber to be deflected away from said opening, said means including a magnetic field of sufiicient strength to restrain current from fiowing through the opening, and means for varying the strength of the field whereby initiation of the discharge is controlled, said ionizable medium having a pressure under operating conditions sufiicient to support an arc-like dischadrge flowing in the presence of said magnetic fiel 20. In combination, an, electron discharge device comprising an envelope containing a cathode, an anode, and an electron-deflecting chamber positioned between the cathode and anode, said chamber having a discharge opening in line with the cathode and anode, a source of electromotive force connected between the cathode and anode, an ionizable medium in said envelope, means mounted exteriorly of the envelope for causing the electrons in the deflection chamber to be deflected away from said opening whereby the number of electrons reaching the anode will be less than required to produce sufiicient cumulative ionization to initiate a discharge within the device, said means including a magnetic field of suflicient strength to restrain current from flowing through the opening, and means for varying the strength of the field whereby initiation of the discharge is controlled, said ionizable medium having a pressure under operating conditions sufiicient to support an arc-like discharge fiowing in the presence of said magnetic field.

21. In the art of controlling the initiation of an arc discharge device, said device being energized by alternating current and comprising an envelope containing a cathode, an anode, a hollow member through which the electrons pass on their way to the anode, an ionizable medium in said envelope at a pressure under operating conditions sufiicient to support an arc-like discharge, the method which consists in magnetically deflecting the electrons emitted by the cathode out of their normal rectilinear paths to such an extent that the number reaching the anode is less than required to produce sufiicient ionization of the. gaseous medium to initiate a discharge during a predetermined portion of the positive half-cycle of the anode voltage and the formation of an arc is restrained during the said portion of the anode voltage cycle.

22. In combination, an electron discharge device comprising an envelope containing a source of electrons, an electron-receiving member and an electrode mounted therebetween, an ionizable medium in said envelope at a pressure under operating conditions suflicient to support an arclike discharge, means for producing a magnetic field which intercepts the direction of said discharge, means including a source of alternating current for energizing said device and for producing an alternating flux in said magnetic means, and means including a source of direct like discharge, means for producing a magenvelope, a plurality of coils on said core. a

netlc field which intercepts the direction of said discharge, said means comprising a metal core having a pole piece mounted transversely of said source of alternating current for energizing said device and one of said coils, and a direct current source for energizing the other of said coils.

24. In the art of controlling the initiation of a gaseous discharge in a device containing a cathode. an anode and an ionizable medium by means of a direct magnetic field, the method which consists in deflecting electrons emitted by the cathode away from the anode by the direct field, thereby preventing cumulative ionization, and varying the direct field by combining therewith, an alternating field in order to determine when the discharge shall start.

25. In the art of controlling the initiation of a gaseous discharge in a device containing electrodes and an ionizable medium by means of a direct magnetic field, the method which consists in utilizing the magnetic field to cause the electrons to move in such a direction as to prevent inelastic collisions with the positive ions of the lonizable' medium, and varying the field by periodically adding and subtracting variable amounts of magnetic field whereby elastic ioniz ing collisions in predetermined amounts between the electrons and positive ions are permitted and the gaseous discharge starts.

26. In the art of controlling the initiation of a gaseous discharge in a device containing a cathode, an anode and an ionizable medium by means of a direct current field, the method which consists in deflecting electrons emitted by the cathode away from'the anode by the field thereby preventing cumulative ionisation, and varying thedirect-fieldbyperiodically adding and subtracting variable amounts of magnetic field whereby cumulative ionisation in a predetermineddegreeispremittedin order tostart-the 2'1. In the art of controlling a gaseous discharge in a device containing a cathode. an anode and an ionizable medium by a direct magnetic field, said device being energized by alternating current and said magnetic field having a maximum strength sui'ilclent to restrain the discharge from flowing during the positive halfcycles oi anode voltage, the method which consists in utilizing the magnetic field to reduce the number of ionizing collisions between the electrons emitted by the cathode and the molecules of the ionizable medium, and varying the-direct field by combining therewith, a variable alternating magnetic field whereby the position in each positive half-cycle of anode voltage at which the gaseous discharge starts may be controlled.

28. In combination, a space discharge device comprising an envelope enclosing two electrodes in an ionizable atmosphere, said electrodes adapted to support a discharge between them, a control unit interposed between said electrodes, said control unit having a conductive surface positioned adjacent the discharge path between .said electrodes, said surface being freely exposed to access by the electrons emitted from said cathode during the absence of said discharge,

means for impressing a magnetic field transverse to the discharge path between said electrodes adjacent said surface, and an electrical connection between said control unit surface and one of said electrodes, the pressure of said atmosphere being sufilciently high to produce substantial ionization upon the starting of said discharge and to cause said discharge to continue in the presence of said transverse magnetic field.

PERCY L. SPENCER.