US3368100A - Vacuum pump having a radially segmented, annular anode - Google Patents

Description

R. G. DETRO 3,368,100

ANNULAR ANODE Feb. 6, 1968 VACUUM PUMP HAVING A RADIALLY SEGMENTE'D 2 Sheets-$heet 1 Original Filed May 24, 1961 SORBEN MA TER/A L INVENTOR: RICHARD G. DETRO, r

H .ATTORNEY.

R. G. DETRO Feb. 6, 1968 VACUUM PUMP HAVING A RADIALLY SEGMENTED, ANNULAR ANODE 2 Sheets-Sheet. 2

Original Filed May 24, 1961 Qk j FIGS.

RNVENTOR RICHARD e. DETRO, BY Q f 2 HIS ATTORNEY.

United States Patent 3,368,100 VACUUM PUMP HAVING A RADIALLY SEGMENTED, ANNULAR ANODE Richard Guy Detro, Scotia, N.Y., assignor to General Electric Company, a corporation of New York Continuation of application Ser. No. 112,392, May 24, 1961. This application May 23, 1966, Ser. No. 552,339

Claims. (Cl. 313-157) ABSTRACT OF THE DISCLOSURE A vacuum pump comprising annular cathodes and an annular anode permitting introduction of the gas to be pumped into the central portion thereof.

This application 552,339 is a continuation of application No. 112,392, now abandoned.

This invention relates to vacuum devices and pertains more particularly to a new and improved vacuum pump utilizing an ionic discharge and to a new and improved high frequency electric discharge device integrally incorporating an ionic pump.

In US. Patent No. 2,755,014 of W. F. Westendorp and A. M. Gurewitsch issued July 17, 1956, and assigned to the same assignee as the present invention is disclosed and claimed a vacuum pump wherein an ionic discharge is utilized in the reduction of gas pressure. This prior device comprises an evacuated envelope defining a space adapted to contain gas molecules, means for ionizing the molecules including cathode and anode members between which electrons are accelerated to ionize the molecules by collision, means for producing a magnetic field extending transverse to the electric field between the cathode and anode elements to increase the length of the path traveled by the electrons before collection by the anode, whereby molecular ionization effects are enhanced, and means for causing sorption of the ionized molecules, whereby the gas pressure in the evacuable envelope is reduced.

The mentioned prior ionic pump, as well as other currently available ionic pumps, are usually attached to an evacuable envelope as an appendage and communicate with the internal volume thereof through a tubulation. In such a device the pumping speed is inversely proportional to the length of the connecting tubulation, and is directly proportional to the cube of the diameter of the passage through the tubulation. in many applications the communication provided by a tubulation between an appended ionic pump and an evacuable envelope is not unduly restrictive. However, in some applications ionic pumps are restricted by the tubulation in the speed with which they can be eiiective in evacuating a device to be evacuated. After a prolonged shutdown period, as during shipment or storage, the evoluation of gas from the materials of which the device is constructed can cause a relatively high pressure therein and damage when the device is first placed in operation. Thus, it is desirable to provide a high speed, high capacity pumping means which will reduce the pressure to a tolerable level substantially immediately upon starting. 1

The present invention contemplatesv an improved ionic pump including means for greatly increasing the pumping capacity thereof. Additionally, the present invention contemplates an improved electric discharge device structure including integrally incorporated ionic pumping means. The electric discharge device can be of the type requiring an operating magnetic field, such as a klystron or magnetron, in which case the ionic pump is operable through the utilization of the same operating magnetic field employed in the operation of the electric discharge device. The presently contemplated ionic pumping means is also adapted for substantially wide ranges of operating parameters in both the magnetic and electric fields and thus, for example, it is not adversely affected by dif ferences in field values which may vary in the manufacture of operating field coils. Further, the present invention contemplates an improved high frequency electric discharge device including integral ionic pumping means which is particularly adapted for avoiding adverse effects in the radio frequency operation of the device, for avoiding the undesired excitation therein of radio frequency resonances, and for minimizing any tendency toward radio frequency leakage from the device as, for example, through the direct current connections for the pump. Still further, the present invention contemplates the provision of ionic pumping structure which is adapted for withstanding substantial mechanical shock and vibration conditions and for withstanding substantially high bake out temperatures to which electric discharge devices in which the pump can be incorporated are normally subjected during manufacture to remove occluded undesired gases. The presently contemplated structure is also particularly adapted for operation and processing in any physically oriented position and, thus, is particularly versatile in its application and the manufacturing processes to which it may be subjected.

Accordingly, the primary object of the present invention is to provide new and improved ionic pumping means which is adapted for performing in an improved manner the functions of prior ionic pumps.

Another object of the present invention is to provide a new and improved ionic pumping means adapted for increased pumping capacity.

Another object of the present invention is to provide a new and improved electric discharge device adapted for normally operating through the use of an operating magnetic field and including new and improved ionic pumping means adapted for operating with the use of the same magnetic field.

Another object of the present invention is to provide a new and improved high frequency electric discharge device including integrally incorporated pumping means which is particularly adapted for rapid sorption of undesired gases and thus is effective for avoiding damage to the device when, for example, after a substantial shutdown period a high volume of evolved gases may be present in the device.

Another object of the present invention is to provide new and improved ionic pumping means which is satisfac torily operable over substantially wide ranges of magnetic and electric field parameters.

Another object of the present invention is to provide a new and improved radio frequency electric discharge device which includes integrally incorporated improved ionic pumping means and is particularly adapted for avoiding adverse effects by the pumping means on the radio frequency operation of the device, for minimizing the excitation of undesired electrical resonances in the pumping means and for minimizing radio frequency leakage through the direct current leads of the pumping means.

Another object of the present invention is to provide new and improved ionic pumping means which is particularly adapted for withstanding substantially high mechanical shock and vibration conditions and which may be operated and processed in any physically oriented position.

Another object of the present invention is to provide new and improved ionic pumping means which is adapted for being subject to substantially high temperature without adverse etfects thereto and thereby is particularly adapted for integral incorporation in devices which during normal processing must be subjected to substantially high temperatures such as those encountered in bake out processes to remove undesired occluded gases.

Futrher objects and advantages of the invention will become apparent as the following description proceeds and the features of novelty which characterize the present invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

In carrying out the objects of the present invention there is provided an electric discharge device of the klystron type including means providing an operating magnetic field extending coaxially therethrough. Integrally incorporated in the tube structure is an annular ionic pump structure comprising a generally toroidal metal pump housing hermetically sealed to the tube envelope about a drift tube section thereof. The pump housing communicates directly with the interior of the tube envelope through a plurality of circumferentially spaced openings in the drift tube section wall. Supported in the pump housing in a suspended and insulative position relative to other elements therein is an annular anode member. The anode member is sub-divided into a plurality of individual cells which extend parallel to the axis of the magnetic field and include radially extending walls which provide each cell with opposed surfaces converging toward the axis of the tube envelope. The inner side walls of the cells include openings facilitating communication between the individual cells and the drift tube sections through the mentioned openings therein. The mentioned suspended support of the anode member is provided by a plurality of circumferentially spaced support rods aifixed to the anode member and mounted in the housing in insulated relation. One of the support rods comprises an anode direct current connector. Additionally, each rod carries means to avoid undesired coating of a ceramic element, whereby the rod is insulated from the housing, with sputtered conductor material from the interior of the pump housing. Supported in conductive relation on. the inner walls of the pump housing on opposite sides of the anode member and in mutually insulative spaced relation thereto are a pair of washer-like titanium cathode elements. The mentioned apertures in the drift tube section are predeterminedly dimensioned to minimize adverse effects on the electron beam as well as undesired electrical resonance of the pump housing and radio frequency losses through the anode direct current lead.

For a better understanding of the invention reference may be had to the accompanying drawing wherein:

FIGURE 1 is a somewhat schematic elevational view of an electric discharge device incorporating an emb'odiment of my invention;

FIGURE 2 is an exploded view illustrating the various elements in the ionic pump structure;

FIGURE 3 is a fragmentary sectional view of the pump structure and drift tube section on which the pump structure is mounted;

FIGURE 4 is an enlarged fragmentary sectional view illustrating in greater detail some of the features of FIG URE 3; and

FIGURE 5 is a partially broken away sectional view taken along the lines 5-5 in FIGURE 1 and looking in the direction of the arrows.

Referring to FIGURE 1, there is shown an electric discharge device of the klystron type generally designated 1. The klystron 1 includes an hermetically sealed evacuated envelope generally designated 2. and includes a cathode structure 3 and an anode structure 4 supported at opposed ends of the envelope. The cathode structure 3 includes an emitter 5 and a heater 6 adapted for being energized by a suitable power source (not shown), and in operation the cathode structure generates a beam of electrons which is projected axially through the device and is collected in the anode structure 4. The beam is effectively collimated by a coaxial operating magnetic field provided by an elongated field coil, or solenoid structure, surrounding the device and generally designated 7.

Between the cathode and anode structure the device comprises a plurality of resonator sections 8 and a plurality of drift tube sections 9 including pairs of opposing ends 10 defining capacitive gaps in the resonant sections. The resonator sections 8 immediately adjacent the cathode structure 3 constitutes an input section and is adapted for being resonated from an external signal source. The ultimate resonator section, or the resonator section immediately adjacent the anode structure 4, constitutes an output section and can include a wave uide output section 11 provided with a suitable hermetically sealed wave guide window structure 12. In accordance with classical klystron operating theory the cathode structure directs a beam of electrons toward the anode structure and the input resonator section velocity modulates the beam which causes bunching of the beam electrons in the drift tube sections. The bunching of the electrons ultimately has the desired effect of predeterminedly resonating the ultimate or output resonator section.

In the operation of the described klystron device it is desirable that the envelope be exhausted to a high degree of vacuum. Such exhaust is accomplished during manufacture. However, during long periods of non-operation, as during shipment or storage, gas may slowly evolve from the elements comprising the device and accumulate in the envelope 2. If this gas should be allowed to accumulate beyond a certain degree, the tube can be severely damaged when it is subsequently operated. Thus, it is desired to provide means which is operable for monitoring the internal pressure condition of the tube before starting and for reducing the pressure to a tolerable limit if undue pressure should be detected.

The present invention satisfies the just-described desiderata. Additionally, it provides means whereby the tube operating magnetic field is employed in reducing the internal gas pressure and whereby the discussed pressure reduction can be effected rapidly to enable early operation of the tube without danger of damage due to the presence of undesired gases therein.

Specifically, the present invention provides for the integral incorporation in the tube structure of an ionic pump generally designated 15. As seen in FIGURE 1 the pump 15 is positioned about the drift tube section 9 interposed between the ultimate, or output, resonator section 8, and the penultimate resonator section. As better seen in FIGURES 1 to 4, the drift tube section 9 about which the pump 15 is disposed is constructed to include a pair of joined tubular sections. This construction facilitates assembly.

Illustrated in FIGURE 2 is an exploded view of the several elements comprising the ionic pump structure. As seen in FIGURES 2 to 4 the pump 15 includes an annular metallic housing 16 formed by a pair of opposed dish-shaped non-magnetic members 17 which can advantageously be formed of stainless steel and which are sealed on the inner rims to the drift tube and to each other at the outer rims.

Supported on each the upper and lower inner surfaces of the housing 16 in conductive contact therewith is a washer-like cathode member 18 formed preferably of titanium. Alternatively, the members 18 can be formed of any other material which is capable of sorbing substantial quantities of gas. Other materials which are employabe in the formation of the members 18 are zirconium, aluminum, carbon, manganese and stainless steel or combinations of these materials. The members 18 are each suitably held in place by a retaining ring 19 secured to the outer wall section of the pump housing and bearing on the outer rim of the member 18, and a pair of cooperating inner retaining rings 20 and 21 which are joined with one bearing on the inner rim of the member 18 and the other suitably secured to the housing member 17 in the manner illustrated in FIGURE 4. Thus, the cathode members 18 are suitably mounted on the opposed inner Wall surfaces of the pump housing 16.

Suspended in the housing 16 between the cathode members 13 and in mutually insulated and spaced relation thereto is an anode structure generally designated 22. The anode structure 22 is annular, and as best seen in FIGURES 2 and 5, is constructed to include a pair of concentrically arranged cylindrical sections 23 and 24 joined by a plurality of circumferentially spaced radially extending metal partitions 25. This construction provides for an anode structure subdivided into a plurality of individual cells all extending through the anode structure parallel to the axes of the device 1 and the operating magnetic field provided by the coil 7 and normal to the planes of the pump cathode members 18. Also, the radial extension of the partitions 25, provides each of the anode cells with opposed divergent wall surfaces, the purpose for which will be brought out in detail hereinafter.

The anode structure 22 is supported in the pump housing 16 in the above-described position by means of a plurality of circumferentially, equally spaced support rods 26 extending through apertures 27 in the upper member 17 of the housing. The outer ends of the rods 26 are secured, as by welding, to appropriate ones of the anode partitions 25. The outer ends of the rods 26 are secured in stand-off insulator constructions generally designated 28 and carried on the upper housing member 17. One of the constructions 28 and its related support rod 26 constitutes the anode direct current connector. In order to facilitate disclosure, only the construction 28 serving as the direct current connector will be described in detail, it being understood that the other construction 28 can be substantially identical except that they are adapted for serving only as insulative supports for the anode structure and not also as power connectors for any of the elements.

As seen in FIGURES 3 and 4, the rod 26 of the anode connector construction extends in spaced relation through one of the apertures 27 in the upper member 148 into a tubular housing extension comprising a pair of upper and lower flanged metal eyelets 3t and 31, respectively. The eyelets 30 and 31 are sealed together at the flanges thereof and the lower eyelet 31 is suitably sealed to the upper surface of the upper member 17 about the aperture 27 therein. Sealed to the upper eyelet 30 is one end of a tubular ceramic insulator 32. Hermetically sealed to the opposite end of the insulator 32 is a metal eyelet 33 in which is sealed the outer end of the support rod 526. Thus, by making electrical contact with the member 33 an electrical connection can be effected to the anode member 22.

In order to insure against the deposition of a coating of conductive material on the inner surface of the ceramic 32 which would subtract from the insulative integrity thereof, there is provided on each of the rods 26 an insulative collar 34 which is disposed in the aperture 27 in the upper member 17. The collar 34 can be formed, for example, of an alumina ceramic and serves to obstruct the passage on conductive material through the aperture 27 and, thus, prevents the deposition of such material on the inner surface of the ceramic 32.

Interconnection of the interiors of the tube envelope 2 and the pump housing 16 is afforded by circumferentially spaced openings or passages 35 formed in the drift tube section 9 about which the pump is disposed. The passages 35 enable passage of any gaseous content of the envelope to be sorbed by the ionic pump into the pump housing from the tube envelope. The gas passage into the individual cells comprising the anode member 22 is facilitated by openings 36 formed in the anode cylindrical member 23 of the pump anode structure.

In operation the field coil 7 provides the operating magnetic field extending through the device 1 and required for collimating the electron beam extending between the cathode and anode structures 3 and 4, respectively, of the tube. Additionally the field coil provides the magnetic field components required to operate the ionic pump 15.

Specifically, the field coil provides magnetic field components extending normal to the cathode members 18 and parallel to the axes of the individual cells provided in the pump anode structure 22. Also, in operation pump housing 16 and, therefore the cathode members 18, are at ground potential and an appropriate positive direct current potential is applied to the pump anode structure 22 by making contact to the member 33. It has been found that the present device can be efiectively operated over a 3 to 1 voltage and magnetic field region. The device operates particularly well at a pump anode potential of 1650 volts at 600 gauss.

With the pump cathode and anode members at the indicated potential cold electric gas discharges are initiated between the cathode members and anode member and free electrons within the housing 16 are accelerated toward the pump positive anode structure 22. However, the free electrons are prevented from reaching the anode member 22 directly by the effects of the magnetic field extending axially through the anode cells. Under the influence of the magnetic field the electrons follow a generally spiraled trajectory along the lines of force of the magnetic field and perform numerous oscillations through the anode cells between the pump cathode members 18. Thus, the paths of the electrons are greatly elongated or extended and the electrons are alforded the opportunity of undergoing numerous collisions with gas molecules present in the device to produce ions by bornbardment before the electrons are collected by the pump anode member 22. Of course, each ionization process creates another electron which is then available for acceleration to produce additional ions. Inasmuch as the gas ions possess a positive charge, they are accelerated toward the negative cathode members 18 and are drawn into these members, whereby they are effectively removed from the space enclosed by the pump housing, thereby to effect a reduction in the gas pressure in the housing.

The above-described general construction involving opposed cathode members and an interposed anode memher and the operation thereof is not part of the present invention but is disclosed and claimed in the above noted U.S. Patent No. 2,755,014. In the presently disclosed structure the sections of the pump comprising each anode cell and cooperating portions of the cathode members can each correspond generally in pumping capacity to one of the prior art pumping devices. By constructing the anode member 22 to include a multiple of cells and arranging the structure coaxially about the tube envelope the present invention provides for substantially greater pumping capacity or capability in rapidly reducing any gas pressure in the tube envelope. Additionally, the coaxial arrangement of the pump about the tube envelope places each of the individual ionic pump combinations in close proximity to the volume to be pumped, namely, the interior of the tube envelope. In this arrangement the connection to the envelope, specifically the passages afforded by the apertures 35 in the drift tube section 9, can be short and of relatively wide diameter. As indicated above, the pumping speed is inversely proportionate to the length of the connecting passages and directly proportional to the cube of the diameter thereof. By constructing the ionic pump so that it surrounds the 'drift tube section and thus bringing the pump elements in close proximity to the tube envelope, it is possible to use a plurality of connections between the pump housing and tube envelope. Also, each connection can be substantially short relative to the tribulation used in prior structures. Specifically, the connection can correspond in length to the thickness of the drift tube section 9. The multiple connections or passages between the tube envelope and the disposition of the pumping elements about the volume to be exhausted thus assist in providing for substantially high pumping capacities.

In order to increase the just-discussed pumping cc.- pacity there are provided openings or apertures 36 in the inner cylindrical element of the anode structure 22. These openings facilitate passage of gases to be sorbed from the tube envelope into the individual cells defined by the pump anode structure which, in turn, facilitates the ionization of the gas for sorption in the above-discussed manner.

It is to be understood from the foregoing that, if desired, the inner cylindrical Wall 23 of the pump anode member can be eliminated completely, thereby to facilitate further gas passage into the anode structure cells. In such a structure the pump anode member could comprise the outer cylinder 24 and radially inwardly extending partitions 25. The structure illustrated in the drawing is believed particularly desirable because of the mechanical strength provided by the inclusion of the inner cylinder 23.

In the disclosed embodiment the convergence of asymmetrical disposition of the walls of the individual anode cells afforded by the radially extending disposition thereof is believed to enhance the pumping operation of the disclosed structure. Specifically, it is believed that this arrangement of the anode walls results in an electric field distribution in the individual anode cells which increases the radii of the electron orbits. This in turn increases the effectiveness of the electrons in creating a plasma or ionization of the gas molecules. Additionally, it is known that the strength of the magnetic field afforded by the field coil will generally vary with different structures. That is, uniformity in field strength is generally not attainable for different structures. For a given electrode construction certain magnetic field strength will not be effective and the device can cut off and not pump in the above-discussed manner. Also, uniformity in the electric fields between the pump anode and cathode members is often diflicult to attain and a predetermined relationship of the electric and magnetic field strengths is required for optimum ionic pumping action.

The convergence of the walls of the pump anode cells adapts the pump for operating effectively over a relatively broad range of magnetic and electric field parameters and thus adapts the device for applications where non-uniformity in magnetic and electric fields may be encountered. That is, for a relatively Wide range of mag netic and electric field values, at least a region between the converging walls of the anode cells will be appropriately spaced for ionic pumping action. If the anode cells were rectangular the inner ionic pumping action would be adversely affected where the optimum magnetic and electric magnetic fields were not provided.

It is to be understood from the foregoing that the convergence of the cell walls or the variance in spacing afforded thereby, can be obtained in any desired manner without departing from the split of the present invention. Thus, the present invention is not limited to the specific ano'de construction shown involving concentric cylindrical members and spaced radially extending cell partitions. The multiple cell construction including opposed converging wall surfaces can be formed in any desired manner.

When the present ionic pump is applied to a high frequency electric discharge device such as the ltlystron illustrated in the drawing it is also desirable to provide means for avoiding adverse effects on the electrical operation of the device and also for avoiding the excitation of certain radio frequency resonances in the pump housing. If certain resonances were permitted to be established in the pump housing high voltage points could result therein which could cause undesirable radio frequency heating of pump elements including the seals as well as radio frequency current leakage out the direct current connector of the anode structure. In the presently disclosed structure the disposition of the ionic pump about a drift tube section the interior of which is relatively free of electric fields, minimizes the tendency toward any adverse effects of the pump structure on the electrical operation of the device. However, the close proximity of the apertures or passages 35 to the velocity modulated electron beam extending through the drift tube sections 9 increases the need for means to avoid excitation of certain resonances in the pump housing.

in order to avoid the undesired excitation of radio frequency resonances in the pump housing 16, the apertures 35 in the drift tube section 9 are predeterminedly dimensioned to cut off electrically at a predetermined radio frequency. For example, the aperture 35 can be dimensioned in accordance with well-known radio frequency engineering practices to cut off electrically, or not pass, radio frequency waves beyond a certain harmonic. This would serve to avoid the establishment or excitation in the housing 16 of resonances having frequencies above the mentioned certain harmonic. Depending on the dimension of the pump housing 16, and therefore the resonances that could be excited therein, and the order of resonances that would be objectionable in the pump housing, the apertures 35 must be prede-terminedly dimensioned to avoid excitation of the objectionable resonances, For example, in the presently disclosed device the apertures are dimensioned to cut off at about the fifth-to-theseventh harmonic.

It is also to be understood from the foregoing that the present invention is not limited to a pump construction which surrounds a tubular section of an evacuable enclosure. If desired, the pump can be provided with an inlet tubulation adapting it for attachment as an appendage to an evacuable enclosure. In such construction, however, the advantages of increased pumping capacity can be attained by making the tubulation co axial to maximize gas passage between the inlet tubulation and the multiplicity of anode cells arranged circumferentially about the axis of the tube. Additionally, a plurality of pump structures of the above-described type can be provided in a stacked array in a single housing for increasing pumping capacity. For example, the inlet tubulation may be defined as the tubulation portion 37 (FIG. 4) of housing 17.

Also, the presently disclosed structure, by virtue of its rugged coaxial construction including the circumferentially spaced multiple suspension of the pump anode member and the metal and ceramic construction, is adapted for withstanding substantially high shock and vibration conditions. It is also adapted for withstanding high temperatures and, in fact, can withstand elevated temperatures up to approximately 900 C. Thus, the pump can be baked out at the same elevated temperatures at which the electric discharge device of which it is an integral part. Still further, the heating and operation of the tube can take place in any oriented position of the ionic pump without adversely affecting the operating capabilities thereof.

If it is desired to monitor the tube 1 for gas content during storage or before operation, it can be done relatively simply by applying an appropriate direct current voltage between the pump housing and pump anode connector 33 while disposing the opposite poles of a permanent magnet on opposite sides of the pump housing. Thus, electric and magnetic field-s are provided to enable temporary operation of the pump and thereby determine any current fiow across the pump that would indicate ionization of containing gas.

While specific embodiment of the present invention has been shown and described it is not desired to limit the invention to the particular form shown and described, and it is intended by the appended claims to cover all modifications within the spirit and scope of the invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

l. An ionic pump comprising in combination,

'(a) a pump housing.

(h) an inlet. tubulation leading into said housing through which gas passes,

(c) an annular cathode surface in said housing adjacent said housing inlet tubulation aperture for the pas- 9 sage of gas from said tubulation and through the defined inner opening of said cathode surface,

(d) a second cathode surface axially spaced from said annular cathode surface,

(e) and an annular grid anode defining a plurality of axially extending individual cells and positioned between and spaced from said cathodes and with its defined inner opening in communication with the said housing inlet tubulation,

(f) said anode comprising at least one circular row of adjacent similar individual axially extending cells in surrounding relationship and parallel to said housing inlet tubulation,

(g) means to apply a potential difference to said electrodes to cause an ionizing gas discharge therebetween,

(h) and magnetic means to provide a magnetic field passing axially through said electrodes to increase ionization for gas entrapment.

2. For use in an ionic pump between spaced gas-entrapping cathode members, an annular grid anode assembly comprising in combination,

'(a) a pair of concentric spaced inner and outer ring wall members defining a central aperture adapted to be placed in communication with a volume to be evacuated,

(b) a plurality of radial wall members between said inner and outer ring wall members in circumferentially spaced relation to define a circular row of a plurality of similar individual unobstructed adjacent cells,

(c) gas passage means through said inner wall member for introducing gas to be entrapped between said radial wall members.

3. An ionic vacuum pump comprising in combination,

(a) an annular envelope having its defined central opening adapted to be placed in communication with a structure in which gas pressure is to be reduced,

(b) a pair of annular cathodes in concentrically spaced apart relationship in said envelope with defined central openings surrounding the central opening of said envelope,

(c) an annular grid anode positioned concentrically in said envelope in spaced relationship between said cathodes,

(d) said annular grid anode defining therein at least one circular row of adjacent individual unobstructed cells between its inner and outer surface with adjacent cell walls including radial partitions extending between said surfaces,

(e) electrical means to provide an electrical discharge between said electrodes to cause ionization of gases in said envelope,

(f) and magnetic means to provide a magnetic field passing axially through said electrodes to increase said ionization for effective gas entrapment in said pump.

4. An ionic pump comprising an evacuable housing defining a space adapted to contain gas molecules, means coupled to said housing for providing ionized gas molecules within said space and including cathode and anode members positioned in spaced apart relationship along a longitudinal axis thereof and between which electrons may pass to cause ionization of said gas molecules, means establishing a magnetic field in said space to cause the path of electrons passing between said cathode and anode members to be greatly elongated to increase the tendency toward ionizing collisions between said electrons and gas molecules, said anode member comprising an element including opposed planar converging wall sections extending parallel to said magnetic field to define a plurality of cells, said cathode member comprising an ion-sorbing material and extending transverse the said axes of said anode member and magnetic field and a fiuid passage in said housing for admitting gas molecules thereinto.

5. An ionic pump comprising an evacuable housing defining a space adapted to contain gas molecules, a tubular section extending coaxially with an axis of and from said housing, means providing communication between the in teriors of said housing and tubular section, means coupled to said housing for providing ionized gas molecules within said space and including a pair of coaxial annular cathode members and a coaxial annular anode member between which electrons must pass to cause ionization of said gas molecules, means establishing a coaxial magnetic field in said space coaxial with said axis to cause the path of electrons passing between said cathode and anode members to be greatly elongated to increase the tendency toward ionizing collisions between said electrons and gas molecules, said cathode members comprising ion-sorbing material and being mounted on the opposed transverse walls of said housing in coaxial relation thereto, said anode being mounted coaxially with said axis in said housing in mutually insulated spaced relation to said cathode members, and said anode member being subdivided into a plurality of cells extending parallel to the axes of said housing and magnetic field by a plurality of circumferentially spaced radially extending partitions.

6. An ionic pump comprising an evacuable housing defining a space adapted to contain gas molecules, said housing being generally annular and including spaced coaxial inner and outer wall sections coaxial with the central longitudinal axis thereof, fluid passage means in the inner wall section of said housing for admitting gas molecules thereinto, means coupled to said housing for providing ionized gas molecules within said space and including annular cathode and anode members spaced along and concentric with said axis and between which electrons may pass to cause ionization of said gas molecules, means establishing a coaxial magnetic field in said space along said axis to cause the path of electrons passing between said cathode and anode members to be greatly elongated to increase the tendency toward ionizing collisions between said electrons and gas molecules, said cathode members comprising a pair of annular ion-sorbing elements mounted on opposed transverse walls of said housing, said anode member being defined by inner and outer concentric cylindrical sections, radial partitions extending between said cylindrical sections to define at least one circular row of adjacent cells, the inner diameter of said anode member being substantially greater than the inner diameter of said housing to position said anode in radially outwardly spaced relationship from the inner wall section of said housing, said inner cylindrical section containing apertures therethrough to admit gas molecules into said cells, said cells extending perpendicular to said cathode members and parallel to the said axis of said housing and magnet, mounted in said housing in mutually insulated spaced relation to said cathode members.

7. An ionic pump according to claim 6 wherein said anode member comprises a spaced pair of concentric cylindrical wall sections and a plurality of circumferentially spaced radial partitions all extending parallel to the axis of said housing, thereby to provide a plurality of individual cells including converging opposed wall surfaces, and the inner cylindrical wall section is apertured at each of said cells to facilitate gas passage into said cells.

3. A high frequency electric discharge device comprising an envelope containing opposed coaxial cooperating electrode elements, means establishing an operating magnetic field extending coaxially with said electrode elements and through said envelope for determining the manner of movement of electrons between said electrode elements, and an ionic pump effective for varying pressure in said envelope, said pump including a conductive pump housing interconnected with said envelope by a plurality of apertures to receive from said envelope any gas molecules contained therein, the said apertures being dimensioned to minimize radio frequency resonances in said housing and said pump further including cooperating pump cathode and anode elements oriented relative to said operating magnetic field to cause the path of electrons passing between the pump cathode and anode members to be greatly elongated to increase the tendency toward ionizing collisions between electrons and gas molecules.

9. A high frequency electric discharge device comprising an envelope containing cooperating coaxial electrode elements, means establishing an operating magnetic field extending coaxially with said electrode elements and through said envelope for determining the manner of movement of electrons between electrode elements, and an ionic pump effective for varying the pressure in said envelope comprising an annular pump housing having a tubular coaxial section of said envelope extending caxially therethrough, a plurality of circumferentially spaced openings interconnecting said housing and said tubular section of said envelope to admit into said housing any gas molecules present in said envelope, means for ionizing said gas molecules in said housing including annular pump cathode and anode members between which electrons may pass to cause ionization of said gas molecules, said pump cathode and anode members being oriented relative to said operating magnetic field to cause the path of electrons passing between said pump cathode and anode members to be elongated to increase the tendency toward ionization in collisions between electrons and gas molecules, said cathode being formed of ion-sorbing material, and said apertures interconnecting said housing and device envelope being dimensioned to avoid excita tion of radio frequency resonances in said pump housing.

10. An electric discharge device comprising an envelope containing opposed cooperating coaxial electrode elements, means establishing an operating magnetic field extending coaxially with said electrode elements and through said envelope for determining the manner of movement of electrons between said electrode elements, and an ionic pump including an annular pump housing having a coaxial section of said envelope extending coaxially therethrough, a plurality of circumferentially spaced openings interconnecting the interiors of said housing and tubular section, and cooperating pump cathode and anode members contained in said housing, said cathode member comprising an annular element of ion-sorbing material extending transverse the axis of said magnetic field, and said anode member comprising a cylindrical wall section and a plurality of circumferentially spaced radial extending partitions all extending parallel to the axis of said magnetic field.

11. A high frequency electric discharge device comprising an envelope containing opposed coaxial cooperating electrode elements, means establishing an operating magnetic field extending coaxially with said electrode elements and through said envelope for determining the manner of movement of electrons between said electrode elements, and an ionic pump including an annular conductive pump housing having a coaxial tubular section of said envelope extending coaxially therethrough, a plurality of circumferentially spaced openings interconnecting the interior of said housing and tubular section, said apertures being dimensioned to avoid excitation of undesired radio frequency resonances in said housing, and cooperating pump cathode and anode members contained in said housing, said pump cathode members comprising a pair of annular members of ion-sorbing material conductively secured to the opposed walls of said housing and trans versely extending relation to the axis of said magnetic field, said pump anode being suspended in said housing in mutually spaced insulated relation between said cathode members and comprising a spaced pair of concentric cylindrical wall sections and a plurality of circumferentially spaced radial partitions all extending parallel to the axis of said magnetic field, thereby to provide a plurality of individual cells including converging opposed Wall sur- Lud faces, and the inner cylindrical wall section of said anode member being apertured at each said cells to facilitate gas passages into said cells.

12. An electric discharge device of the klystron type comprising an envelope including at least one drift tube section, an anode element, a cathode element adapted for directing a beam of electrons through said drift tube section into said anode element, means establishing an operating magnetic field extending coaxially with said drift tube and through said envelope for collimating said electron beam in said drift tube section, and an integral ionic pump comprising an annular pump housing surrounding said drift tube section and communicating with the interior of said envelope through a plurality of circumferentially spaced passages in said drift tube section to admit into said housing any gas molecules present in said envelope, and means for ionizing said gas molecules in said housing including pump anode and cathode members between which electrons may pass to cause ionization of said gas molecules, said pump cathode and anode members being oriented relative to said operating magnetic field to cause the path of electrons between said pump cathode and anode members to be greatly elongated to increase the tendency toward ionizing collisions between electrons and gas molecules.

13. An electric discharge device according to claim 12, wherein said passages interconnecting said envelope and housing are dimensioned to avoid excitation of radio frequency resonances in said housing.

14. The invention as recited in claim 1 wherein at least one of said cathodes includes titanium.

15. An ionic pump comprising in combination,

(a) a pump housing,

(b) an inlet tubulation leading into said housing through which gas passes,

(c) an annular cathode surface in said housing adjacent said housing inlet tubulation aperture for the passage of gas through its defined inner opening,

((1) a second cathode surface axially spaced from said annular cathode surface,

(e) and an annular grid anode defining a plurality of axially extending individual cells and positioned between and spaced from said cathodes and with its defined inner opening in communication with the said housing inlet tubulation,

(f) said anode comprising at least one circular row of adjacent similar individual axially extending cells in surrounding relationship and parallel to said housing inlet tubulation, defined by a circular wall section, a plurality of peripherally equally spaced transverse wall sections extending from said circular wall sec tion to define axially extending glow discharge passages therebetween and between said cathodes,

(g) means to apply a potential difference to said electrodes to cause an ionizing gas discharge therebetween,

(h) and magnetic means to provide a magnetic field passing axially through said electrodes to increase ionization for gas entrapment.

References Cited UNITED STATES PATENTS 3,070,283 12/1962 Hall 3137.3 2,913,167 11/1959 Herb 3l37.3 2,993,633 7/1961 Hall 230-69 3,088,657 5/1963 Zaphiropoulos 230-69 3,231,175 1/1966 Zaphiropoulos 230-69 JAMES W. LAWRENCE, Primary Examiner.

STANLEY D. SCHLOSSER, Examiner.

S. A. SCHNEEBERGER, Assistant Examiner.

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