US3460745A - Magnetically confined electrical discharge getter ion vacuum pump having a cathode projection extending into the anode cell - Google Patents

Magnetically confined electrical discharge getter ion vacuum pump having a cathode projection extending into the anode cell Download PDF

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Publication number
US3460745A
US3460745A US662635A US3460745DA US3460745A US 3460745 A US3460745 A US 3460745A US 662635 A US662635 A US 662635A US 3460745D A US3460745D A US 3460745DA US 3460745 A US3460745 A US 3460745A
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cathode
discharge
anode
posts
pump
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US662635A
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Lawrence T Lamont Jr
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Varian Medical Systems Inc
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Varian Associates Inc
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J41/00—Discharge tubes for measuring pressure of introduced gas or for detecting presence of gas; Discharge tubes for evacuation by diffusion of ions
    • H01J41/12—Discharge tubes for evacuating by diffusion of ions, e.g. ion pumps, getter ion pumps
    • H01J41/18—Discharge tubes for evacuating by diffusion of ions, e.g. ion pumps, getter ion pumps with ionisation by means of cold cathodes
    • H01J41/20—Discharge tubes for evacuating by diffusion of ions, e.g. ion pumps, getter ion pumps with ionisation by means of cold cathodes using gettering substances

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  • getter ion pumps have been proposed employing cathode projections extending toward but not into the glow discharge passageways in the anode structure, such projections being coaxially aligned with such glow discharge passageways.
  • getter ion pumps have been proposed employing cathode projections extending toward but not into the glow discharge passageways in the anode structure, such projections being coaxially aligned with such glow discharge passageways.
  • One such prior art pump is described and claimed in US. Patent 3,112,863, issued Dec. 3, 1963.
  • Such prior cathode projections provided a cathode surface at glancing angles of incidence with the ion trajectories, thereby increasing the rate of sputtering of cathode material onto the remaining portions of the cathode structure.
  • the increased rate of sputtering was not sufficient to allow a diode type pump to provide stable operation for pumping of noble gases.
  • the pump was made stable for pumping noble gases by insulating the cathode projections from the remaining portions of the cathode structure and operating the cathode projections at a more negative potential than the remaining portion of the cathode.
  • the ions that were collected on the remaining portion of the cathode, in regions of net buildup of sputtered cathode material, were collected at a potential more positive than that of the cathode projections such that the ions incident in theregion of net buildup of getter material were slowed down to prevent resputtering the collected material with release of the trapped gases.
  • cathode projections were provided in a diode pump.
  • the projections extended coaxially into the anode glow discharge passageways for substantially the entire length of the passageways to define a magnetron type pump. While such a magnetron pump provides improved starting characteristics at low pressures, i.e., pressures less than 10 torrs, it provides relatively low but stable noble gas pumping speeds since the regions of net buildup of cathode material occur on the end plates and relatively few noble gas ions are driven into the end plates to be covered up by subsequently sputtered cathode material.
  • a magnetron type pump is described in US. Patent 2,993,638, issued July 25, 1961, and assigned to the same assignee as the present invention.
  • the principal object of the present invention is the provision of an improved magnetically confined electrical discharge getter ion vacuum pump having improved noble gas handling capability.
  • One feature of the present invention is the provision, in a discharge getter ion pump, of a cathode projection extending into at least one of the discharge passageways of the anode, such cathode projection terminating at a point along the length of the discharge passageway which is less than midway therein to define a combined Penning discharge and magnetron discharge region in the discharge passageway of the anode, whereby the capacity of the pump for pumping noble gases is enhanced.
  • cathode projection is made of a body centered cubic material, whereby the sputtering rate from the cathode projection is increased as compared to hexagonal close packed material such as titanium which has been employed heretofore.
  • cathode projection is a cylindrical post, whereby sputtering is obtained from the free end of the post as well as from the sides of the post.
  • Another feature of the present invention is the same as the first or second features wherein the cathode projection is formed by a folded metal member with the folded portion projecting into the anode discharge passageway, whereby fabrication of the cathode projection is facilitated.
  • Another feature of the present invention is the same as any one or more of the preceding features wherein the cathode projection is insulated from the remaining portion of the cathode and operated at a potential independent of both the anode potential and the other cathode potential, whereby a triode pump configuration is obtained.
  • FIG. 1 is a sectional view of a discharge getter ion pump incorporating features of the present invention
  • FIG. 2 is a reduced sectional view of an alternative embodiment of a portion of the structure of FIG. 1 delineated by line 2--2,
  • FIG. 3 is a fragmentary sectional view of an alternative embodiment of the present invention.
  • FIG. 4 is a fragmentary sectional view of an alternative embodiment of the present invention.
  • FIG. 5 is a sectional view of a portion of the structure of FIG. 4 taken along line 5-5 in the direction of the arrows,
  • FIG. 6 is a fragmentary sectional view of an alternative embodiment of the present invention.
  • FIG. 7 is a plot of ion current I vs. pressure P depicting the ion current characteristics of the pump of the present invention as compared with the prior art pumps.
  • FIG. 1 there is shown a magnetically confined electrical discharge getter ion pump incorporating features of the present invention.
  • the pump includes a hollow vacuum envelope 2 having an inlet port 3 in gas communication with a device to be evacuated, not shown.
  • a hollow cylindrical anode structure 4 is disposed within the envelope 2 between a pair of cathode plates 5 which are made of a suitable getter material such as for example titanium.
  • a pair of cathode projections 6, such as cylindrical posts, are coaxially aligned with the axis of the cylindrical anode 4 and extend from the cathode plates 5 to well within the anode cylinder 4.
  • the posts 6 terminate at a point within the cylindrical anode 4 which is substantially less than midway along the length of the cylindrical discharge passage in the cylindrical anode 4.
  • the midpoint of the cylindrical anode 4 is defined by the line identified by 7.
  • the vacuum envelope 2 is disposed between the poles of a permanent magnet 8 for producing a discharge confining magnetic field B which is directed axially through the electrical discharge passageway 4 in the anode structure.
  • the cathode posts 6 and cathode plates 5 are electrically connected to the envelope 2 which is operated at ground potential.
  • the anode structure 4 is supported on a conductive rod 9 which extends out of the vacuum envelope 2 through a feed-through insulator assembly 11.
  • the rod 9 is connected to a power supply 12 for operating the anode 4 at a suitable positive potential with respect to ground such as +6 kv.
  • the feed-through insulator assembly 11 includes a cylindrical insulator member 13 as of alumina ceramic sealed at one end to the envelope 2 and at the other end to a metallic diaphragm 14 which is sealed to the post 9.
  • An annular sputter shield 15 is carried upon the rod 9 to shield the insulator 13 from sputtered cathode material.
  • the pump is first evacuated by means of a suitable mechanical or sorption pump, not shown, to a pressure on the order of torrs.
  • the anode potential is then applied to initiate a magnetically confined electrical discharge in the gas within the hollow interior of the cylindrical anode structure 4.
  • the inside wall of the cylindrical anode structure defines a discharge passageway axially aligned with the magnetic field B.
  • the axial extent of the posts 6, which is coextensive with the end portions of the discharge passageway, defines magnetron interaction regions 16 and 17 at the ends of the discharge passageway. In the region between the free ends of the posts 6, there is defined a magnetically confined Penning discharge region 18.
  • a certain fraction of the positive ions generated within the Penning discharge region 18 bombard the posts 6. Certain of these ions are generated on the axis of the discharge passageway and bombard the free end portions of the posts 6. Upon bombardment of the ends of the posts by the positive ions, getter material is sputtered from the ends of the posts along straight lines radiating away from the ends of the posts. A substantial percentage of the sputtered material is collected in an annular ring on the opposed cathode plate 5 as indicated by dotted lines 19. This sputtered material results in a net buildup of collected getter material into which noble gas ions may be buried and covered over by subsequently collected getter material on the cathode plates 5.
  • Certain other ions generated off the axis of the Penning discharge region 18 bombard the sides of the posts 6 resulting in additional sputtering of cathode material from the posts onto the cathode plates 5.
  • a preponderance of these ions bombard the posts 6 at glancing angles of incidence, thereby resulting in increased sputtering from the posts as compared to ions whch strike the posts at angles normal to the surface of the posts.
  • These ions which bombard the posts with glancing angles of incidence cause a preponderance of the sputtered material to be sputtered along rays leaving the cathode surface at substantially the same angle as the angle of incidence of the impinging ions.
  • the glancing angle of incidence ions produce lobes of sputtered material, indicated at 20, which further add to the net buildup of cathode material in the annular ring pattern indicated at 19.
  • Other ions which do not intercept posts 6, bombard the cathode plates 5 principally in the region of most intense net buildup of sputtered cathode material where they are either gettered or buried by subsequently sputtered cathode material.
  • FIG. 1 It is found that the pump configuration of FIG. 1 is especially useful for pumping noble gases due to the relatively large net buildup of sputtered cathode material on the cathode plates 5.
  • the cathode posts 6 are made of a body centered cubic material such as zirconium, molybdenum or tantalum to increase the rate at which the cathode material is sputtered from the posts as compared to prior cathode materials such as titanium which is hexagonal close packed material and, therefore, relatively difiicult to sputter at glancing angles compared to body centered cubic material. Tantalum is found to be especially useful for pumping gases such as air which contain a substantial amount of hydrogen, which comes from dissociation of water vapor, since solubility of hydrogen in tantalum is on the order of 20,000 times greater than the solubility of hydrogen in molybdenum.
  • a body centered cubic material such as zirconium, molybdenum or tantalum
  • Prior art serrated cathode plates as employed in diode type pumps, have provided a pumping speed for argon which is approximatley 6% of the pumping speed of nitrogen.
  • the pumping speed for argon was approximately 26% of the pumping speed for nitrogen, thus representing approximately a four times increase in the pumping speed for noble gasses as compared to prior art diode pumps using serrated cathode plates.
  • the pump of FIG. 1 pumps active gases at about the same rate as prior art diode pumps.
  • the cathode posts 6 preferably have a diameter less than 20% of the diameter of the discharge passageway to prevent producing too great a disturbance in the electric field geometry of the discharge cell and intercepting dcposition of sputtered cathode material onto the cathode plates 5.
  • the cathode posts 6 should not be too small in diameter, or else substantially no sputtering will be obtained from the posts 6. More specifically, the posts 6 preferably have a diameter greater than 0.030 inch.
  • FIG. 2 there is shown an alternative embodiment of the present invention.
  • the structure is substantially the same as that described with regard to FIG. 1 with the exception that cathode posts 6 which project into the discharge passageway in the anode 4 are of a conical shape as opposed to the cylindrical shape of the posts 6 of FIG. 1.
  • the mode of operation is substantially the same as that previously described with regard to FIG. 1 with the exception that the axial alignment of the conical posts 6 is more critical than that of the cylindrical posts 6 since slight misalignment of the conical posts 6 with respect to the axis of the discharge passageway results in substantially reduced sputtering from the ends of the conical posts 6.
  • FIG. 3 there is shown an alternative embodiment of the present invention.
  • the structure is substantially identical to that previously described with regard to FIG. 1 except that the anode structure 4 includes a plurality of discharge passageways coaxially aligned with the discharge confining magnetic field B.
  • the multiple discharge passageway anode and pumps using same have increased pumping capacity, the pumping capacity being increased with an increase in the number of anode cells.
  • FIGS. 4 and 5 there is shown an alternative embodiment of the present invention.
  • the structure is substantially the same as that previously described with regard to FIG. 3 with the exception that the cathode projections which extend into the discharge passageways of the anode structure 4 are formed by a folded piece of sheet metal which is serrated at 25 to form the cathode projections 6".
  • the folded metal structure is made of a suitable getter material, as previously described for the posts 6.
  • the folded metal structure may be aflixed to the cathode plates 5 or suspended above the cathode plates 5 by a suitable support structure, not shown.
  • the folded metal cathode projections 6" function in essentially the same manner as the cathode posts 6 and 6 previously described with regard to FIGS. 1 and 2.
  • FIG. 6 there is shown an alternative embodiment of the present invention similar to that shown in FIG. 4 except modified such that the cathode structure 6" which projects into the anode discharge passageways 4 may be operated at a potential more negative than the cathode plates 5 to obtain a triode pump configuration.
  • the apparatus is substantially identical to that of FIG. 4, except that the folded metal cathode projections 6" are supported from the cathode plates 5 via insulative members 26 to permit the cathode projections 6" to be operated at a cathode potential independent of the cathode plates -5.
  • a power supply 27 is connected to the cathode structures 6" via leads 28 for operating the cathode projections 6" at a potential more negative than the cathode plates 5 by, for example, 2000 v.
  • FIG. 7 there is shown a plot of ion current I vs. pressure P depicting the characteristics of ion getter pumps of the present invention as contrasted with those of the prior art. More specifically, the dotted line 29 depicts the typical ion characteristic of the prior art diode pump employing magnetically confined Penning discharge cells. In this instance, the ion current I decreases with decreases in pressure until the discharge is extinguished. 0n the other hand, the characteristic for the present pump is shown at 31. It is seen from characteristic 31 that the ion current I decreases with decreasing pres sure until a certain low pressure regime is reached at which time the current tends to level out and not to decrease further with decreases in the pressure.
  • the discharge current I is increased as compared to the prior open cell geometry. This facilitates starting of the ion pumps in the low pressure regime and permits the pump to operate down to lower pressures. It is believed that the improved low pressure ignition is facilitated by field emission from the posts 6. It has been observed that the pump discharge readily strikes with anode potentials on the order of 3,000 v. at pressures less than 3 1O* torrs.
  • the ion pump of the present invention has been described employing a pair of cathode projections 6 extending into the discharge anode passageway from opposite ends, this is not a requirement. If desired, only one cathode projection need extend into the discharge passageway. However, the pumping speed will be reduced compared to a geometry employing cathode projections extending from opposite ends of the discharge passageway.
  • an ion getter vacuum pump apparatus means forming an anode structure having at least one discharge passageway therein, means for producing a magnetic field within and generally axially directed of said discharge passageway for magnetically confining the discharge, means forming a cathode structure spaced from said anode structure, said cathode structure being made of a getter material, means forming an insulative structure for insulating said anode structure from said cathode structure to permit an electrical potential to be applied between said anode and cathode structures to establish a magnetically confined electrical discharge therebetween to produce ions for bombarding said cathode structure to sputter cathode getter material onto collecting surfaces within the pump for getter gases within the vacuum pump apparatus, said cathode structure including at least one projection of getter material extending from said cathode structure coaxially of said discharge passageway in said anode structure and from which getter material is sputtered in use, the improvement wherein said cathode projection extends into said discharge
  • cathode projection is elongated and made of a body centered cubic material, whereby the sputtering from the projection is increased.
  • cathode projection is made of tantalum, whereby the solubility of hydrogen in the getter material sputtered from said projection has a relatively high value as compared to molybdenum.
  • cathode projection is an elongated cylindrical post coaxially aligned with the axis of said discharge passageway in said anode structure.
  • cathode post has a diameter less than 20% of the diameter of the coaxial discharge passageway and a diameter greater than 0.030 inch.
  • said cathode structure includes a plate having said cathode post conductively affixed thereto and extending therefrom into said anode discharge passageway, and wherein said anode passageway has uniform cross sectional dimensions over substantially its entire length.
  • said anode struc ture includes a plurality of parallel discharge passageways
  • said cathode structure includes a plurality of elongated cathode projections extending coaxially into said discharge passageways and terminating at points within said discharge passageways substantially less than midway along the length of said passageways.
  • a pair of said cathode projections are elongated post structures and extend into said discharge passageway from opposite ends of said passageway in coaxial alignment therewith and with each other, each of said elongated cathode projections terminated within said discharge passageway at points substantially less than midway along the length of said passageway.
  • said cathode structure includes a pair of plates disposed on opposite sides of said anode and having said elongated cathode post structures projecting therefrom in coaxial alignment with said discharge passageways and terminating at a point substantialy less than halfway along the length of said discharge passageway, said discharge passageways being open at both ends and extending through said anode with the open ends of said discharge passageways terminating in a pair of planes axially spaced from the plane of said cathode plates, and said elongated cathode posts including pairs of said posts extending into a plurality of said discharge passageways from both ends thereof to define a plurality of discharge passageways having magnetically confined Penning discharge regions in the central regions of said discharge passageways be- References Cited UNITED STATES PATENTS 7/1961 Hall et a1. 230-69 3/1966 Noller 23069 ROBERT M. WALKER, Primary Examiner US. Cl. X.R. 3137

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US662635A 1967-08-23 1967-08-23 Magnetically confined electrical discharge getter ion vacuum pump having a cathode projection extending into the anode cell Expired - Lifetime US3460745A (en)

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DE (1) DE1764782A1 (fr)
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Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3942546A (en) * 1972-10-27 1976-03-09 Continental Oil Company Corrosion monitoring and composition-analytical apparatus
US4097195A (en) * 1975-02-12 1978-06-27 Varian Associates, Inc. High vacuum pump
WO1987004005A1 (fr) * 1985-12-19 1987-07-02 Hughes Aircraft Company Passage traversant d'alimentation a haute tension pour pompe ionique
US5655886A (en) * 1995-06-06 1997-08-12 Color Planar Displays, Inc. Vacuum maintenance device for high vacuum chambers
US6004104A (en) * 1997-07-14 1999-12-21 Duniway Stockroom Corp. Cathode structure for sputter ion pump
US6220821B1 (en) * 1999-05-20 2001-04-24 Kernco, Incorporated Ion pump having protective mask components overlying the cathode elements
US20040062659A1 (en) * 2002-07-12 2004-04-01 Sinha Mahadeva P. Ion pump with combined housing and cathode
EP2937891A1 (fr) * 2014-04-24 2015-10-28 Honeywell International Inc. Micro pompe ionique triode/différentielle hybride
US20160233062A1 (en) * 2015-02-10 2016-08-11 Hamilton Sunstrand Corporation System and Method for Enhanced Ion Pump Lifespan
US20180068836A1 (en) * 2016-09-08 2018-03-08 Edwards Vacuum Llc Ion trajectory manipulation architecture in an ion pump
US9960026B1 (en) * 2013-11-11 2018-05-01 Coldquanta Inc. Ion pump with direct molecule flow channel through anode
US9960025B1 (en) * 2013-11-11 2018-05-01 Coldquanta Inc. Cold-matter system having ion pump integrated with channel cell
US10262845B2 (en) 2015-02-10 2019-04-16 Hamilton Sundstrand Corporation System and method for enhanced ion pump lifespan
US10629417B1 (en) * 2016-12-01 2020-04-21 ColdQuanta, Inc. Sputter ion pump with penning-trap current sensor

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102009040356A1 (de) 2009-09-05 2011-03-17 Schmidt, Linda Elktrodenanordnung für eine Ionengetterpumpe

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2993638A (en) * 1957-07-24 1961-07-25 Varian Associates Electrical vacuum pump apparatus and method
US3239133A (en) * 1961-04-01 1966-03-08 Leybold Holding A G E Pump

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2993638A (en) * 1957-07-24 1961-07-25 Varian Associates Electrical vacuum pump apparatus and method
US3239133A (en) * 1961-04-01 1966-03-08 Leybold Holding A G E Pump

Cited By (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3942546A (en) * 1972-10-27 1976-03-09 Continental Oil Company Corrosion monitoring and composition-analytical apparatus
US4097195A (en) * 1975-02-12 1978-06-27 Varian Associates, Inc. High vacuum pump
WO1987004005A1 (fr) * 1985-12-19 1987-07-02 Hughes Aircraft Company Passage traversant d'alimentation a haute tension pour pompe ionique
US5655886A (en) * 1995-06-06 1997-08-12 Color Planar Displays, Inc. Vacuum maintenance device for high vacuum chambers
US6004104A (en) * 1997-07-14 1999-12-21 Duniway Stockroom Corp. Cathode structure for sputter ion pump
US6220821B1 (en) * 1999-05-20 2001-04-24 Kernco, Incorporated Ion pump having protective mask components overlying the cathode elements
US20040062659A1 (en) * 2002-07-12 2004-04-01 Sinha Mahadeva P. Ion pump with combined housing and cathode
US10460918B2 (en) * 2013-11-11 2019-10-29 Coldquanta, Inc Forming ion pump having silicon manifold
US9960026B1 (en) * 2013-11-11 2018-05-01 Coldquanta Inc. Ion pump with direct molecule flow channel through anode
US9960025B1 (en) * 2013-11-11 2018-05-01 Coldquanta Inc. Cold-matter system having ion pump integrated with channel cell
CN105047516A (zh) * 2014-04-24 2015-11-11 霍尼韦尔国际公司 微混合差分/三极管离子泵
EP2937891A1 (fr) * 2014-04-24 2015-10-28 Honeywell International Inc. Micro pompe ionique triode/différentielle hybride
US10665437B2 (en) * 2015-02-10 2020-05-26 Hamilton Sundstrand Corporation System and method for enhanced ion pump lifespan
US20160233062A1 (en) * 2015-02-10 2016-08-11 Hamilton Sunstrand Corporation System and Method for Enhanced Ion Pump Lifespan
US11742191B2 (en) * 2015-02-10 2023-08-29 Hamilton Sundstrand Corporation System and method for enhanced ion pump lifespan
US10262845B2 (en) 2015-02-10 2019-04-16 Hamilton Sundstrand Corporation System and method for enhanced ion pump lifespan
US20210327695A1 (en) * 2015-02-10 2021-10-21 Hamilton Sundstrand Corporation System and method for enhanced ion pump lifespan
US11081327B2 (en) * 2015-02-10 2021-08-03 Hamilton Sundstrand Corporation System and method for enhanced ion pump lifespan
CN107808810A (zh) * 2016-09-08 2018-03-16 爱德华兹真空泵有限责任公司 离子泵中的离子轨道操纵构造
US10550829B2 (en) * 2016-09-08 2020-02-04 Edwards Vacuum Llc Ion trajectory manipulation architecture in an ion pump
US20180068836A1 (en) * 2016-09-08 2018-03-08 Edwards Vacuum Llc Ion trajectory manipulation architecture in an ion pump
US10629417B1 (en) * 2016-12-01 2020-04-21 ColdQuanta, Inc. Sputter ion pump with penning-trap current sensor

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GB1191223A (en) 1970-05-13
CH505462A (de) 1971-03-31
DE1764782A1 (de) 1971-11-11
FR1585970A (fr) 1970-02-06

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