US3251536A

US3251536A - Getter-ion pumps

Info

Publication number: US3251536A
Application number: US314795A
Authority: US
Inventors: Thomas A Connor
Original assignee: Consolidated Vacuum Corp
Current assignee: Consolidated Vacuum Corp
Priority date: 1963-10-08
Filing date: 1963-10-08
Publication date: 1966-05-17
Anticipated expiration: 1983-05-17

Description

May 17, 1966 T. A. CONNOR 3,251,536

GETTER-ION PUMPS Filed oct. a, 196s s sheets-sheet 1 l 5i Z 55 Ww @y INVENTOR THM/4 ,4. 60A/Na May 17, 1966 T. A. CONNOR GETTER-ION PUMPS Filed Oct. 8, 1965 3 Sheets-Sheet 2 iff Arran/n".

May 17, 1966 T. A. CONNOR 3,251,536

GETTER-ION PUMPS I Filed OCT.. 8, 1965 3 Sheets-Sheet 5 INVENTOR. TMm/4;' ,4. 00AM/0f? United States Patent O M 3,251,536 GETTER-IUN PUMPS Thomas A. Connor, Hilton, N Y., assignor to Consolidated Vacuum Corporation, Rochester, N.Y., a corporation of New York Filed Get. 8, 1963, Ser. No. 314,795 5 Claims. (Cl. 230-69) The subject invention relates to getter-ion pumps and, more particularly, to getter material sources for these pumps.

Getter-ion pumps are well known. They comprise a pump housing and means for ionizing gas molecules in the pump housing and for entrapping the ionized gals molecules on a molecule collecting surface in the pump housing. The means for ionizing gas molecules usually comprise at least one grid-shaped anode and a hot or a cold cathode for releasing electrons to the anode. These electrons collide with and 'thus ionize gas molecules present in the pump housing. In many instances,

the pump housing itself is negatively biased and is utilized as a cold cathode for releasing electrons from part of its inner surface to the anode. Similarly, the inner surface of the pump housing is frequently utilizedas the above-mentioned molecule collecting surface and is negatively biased for this purposeso as to attract ionized gas molecules.

Known getter-ion pumps include a source of getter material, such as vaporized titanium. The getter material is released in the pump housing togetter gas molecules present therein and particularly gas molecules present on the above-mentioned collecting surface. In some types of getter-ion pumps, the gettering action is carried on independently `of the gas molecule ionizing operation. In these pumps, the source of getter material is positioned to deposit getter material on a part of the inner surface of the pump housing that is separate from the part on which ionized gas molecules are entrapped. In -this case, the part of the pump which includes the source of getter material acts as a type of fore-pump for the part of the pump which includes the gas molecule ionizing means.

In known pumps the, source of getter material comprises an evaporation post, a supply of getter material wire, such as titanium wire, means for feeding the getter Wire to the evaporation post, and means including an electric power source forcausing vaporization of getter material from the wire at the evaporation post. These known sources `of getter material have several disadvantages, lsuch as susceptibility to getter wire misalignment with respect to the evapora-tion post, welding of the getter wire to the post with resultant impairment or failure of the electric power source, wear and failure of the wire feeding means including galling and jamming thereof, progressive deterioration of the evaporator post, and rupture of the getter Wire. In addition, these known sources require the provision and-maintenance of cumbersome drives for the getter wire. The subject invention overcomes these disadvantages and provides a' getter material source comprising a solid bar of getter material and means ,for heating the solid bar at a surface thereof to cause release of vaporized getter material into the pump housing and onto the molecule collecting surface thereof. As mentioned above, this molecule collecting surface may be that part of the inner surface of the pump housing at which ionized gas molecules are collected, or it may be' a part of the inner surface of the pump housing which is separate from the part at -which ionized gas molecules are collected. If desired, the molecule collecting surface or surfaces may also be on an electrode or electrodes that are inside of, but separate from, the pump housing.'

3,Z5i,536 Patented May 17, 1966 The expression solid bar of getter materialfas used herein is meant to refer to solid blocks of bulk getter material, to elongated solid `bars of getter material, to solid rods of getter material other than wires, to solid slugs of getter material, and to similar solid bodies of getter material that are capable of supplying vaporized getter material for several hours of pumping operation without having to be replenished with fresh getter material or Without having to be supplied to a vaporization point in the form of a wire, tape or similar body. To name an example, the getter material may be titanium.

The means for heating the solid bar of getter material, in preferred embodiments of the inve-ation, comprise an electron gun for bombarding a surface of the solid bar of getter material to cause release of vaporized getter material therefrom. The electron gun includes means for focusing the electrons released by the gun in the form of an electron -beam onto the above-mentioned 'surface of the solid bar. If this surface is rather large, deiiection means, such as magnets may be employed for continuously scanning the electron beam over the surface. In this manner, a substantially uniform vaporization of getter material takes place.

If desired, a filament may be employed for heating the solid bar of getter material. This filament is placed in the vicinity of the surface of thevsclid bar from which vaporized getter material is to be released. The filament is heated by an electric current and the solid bar of getter material is biased positively with respect to the filament, so that the filament releases electrons onto the above-mentioned surface thereof and causes release of vaporized getter material therefrom. The bar of getter material is preferably mounted to be movable with respect to the filament, so that the distance between the bar and the filament may be adjusted as getter material is evaporated from the bar.

The invention will become more readily apparent from the following detailed description of preferred embodiments thereof, illustrated by way of example in the accompanying drawings, in which:

FIG. 1 is a longitudinal section of a getter ion pump in accordance with a first embodiment of the invention;

FIG. 2 is a longitudinal section of a getter' ion pump in accordance with a second embodiment of the invention;

FIG. 3 is a side view of a detail of the pump illustrated in FIG. 2;

FIG. 4 is a longitudinal section of a getter ion pump in accordance with a third embodiment of the invention;

FIG. 5 is a plan view of a detail of the pump illustrated in FIG. 4; and

FIG. 6 is a fractional longitudinal view of a getter-ion pump in accordance with a fourth embodiment of the invention.

Y The getter-ion pump shown in FIG. 1 comprises a cylindrical housing 10` defining flanges 11 and 12 and an inlet opening 13l at fiange 12. A tube 15 is connected to inlet opening 13 and has a flange 16 which is sealed 'to flange 12 by a sealing ring 17 and a number of bolts one of which is shown at 18. The tube 15 leads to a space or vessel (not shown) to be evacuated. As is well known, the space or vessel to be evacuated may be pre-evacuated by a conventional roughing pump (not shown) connected thereto. The pump housing 10 is closed by a cover 20 which is sealed to flange 11 by a sealing ring 21 and a number of bolts, one of which is shown at 22. A cylindrical anode grid Z4 is mounted in housing 10. During operation of the pump, a directcurrent, high voltage power source 25 biases anode 24 positively with respect to housing 10. To this effect, a lead 26 extends from a negative terminal 27 of source 25 to housing 10, and a lead 28 extends from a positive terminal 29 of source 25 to the anode 24, through an insulating bushing 30 in .housing 10. A filament 150 is disposed below anode grid 24 and is connected by a pair of

leads

151 and 152, which extend

throughinsulating bushings

154 and 155 in housing 1t), to a filament power supply 156. A wire 157 connects the lead 151 to the above-mentioned lead 26. The filament 150 serves to release electrons to anode grid 24 and to the space encompassed thereby. These electrons will strike and ionize gas molecules present in the latter space. The ionized gas molecules are attracted by the negatively biased housing 16 and deposit themselves on the inner surface 3-2 of housing 10, which thus serves as a collecting surface. In this manner, gas molecules are continuously pumped from the space to be evacuated. If desired, the filament 150 may also be disposed in a location other than that shown. For example, the filament 150 may be located above anode grid 24. For the purpose of simplicity, the filament 150' has not been shown in FIGS. 1 to 6. It will also be understood that the getter material bars shown herein may be capable of releasing ionizing electrons to the anode grid 24.

To assist this pumping action, and also to create an environment in which the ion pump system so far described is most effectively operated, the pump shown in FIG. 1 includes a bar of getter material, such as titanium, in the form of a solid rod 33. This rod is mounted on a support 34 to extend along part of the longitudinal axis 100 through cylindrical housing 10. The support 34 is mounted on housing by brackets 35. The cover 20 has a centralnipple 37 defining a fiange 38. A circular disc 39 is sealed to flange 38 by a sealing ring 40 and a number of bolts 41. The disc 39 defines a threaded centralopening 42 having a shoulder portion 43 associated therewith. An electron gun 45 has a housing 46 with a threaded end portion 47. End portion 47 of gun 4S is threaded into opening 42 of disc 39 and is sealed thereto by a sealing ring 48 located between the end portion 47 and the shoulder portion 43.

The electron gun 45 includes a cathode filament 50, a pair of electron beam forming and accelerating

electrodes

51 and 52, and a magnetic focussing coil 53. The filament 50` is energized with heating current from the secondary winding 55 of a transformer 56, by a pair of leads 57 and 58 which extend through insulating bushings 60 and 61 in gun housing 46. The transformer 56 has a primary winding 62 one end of which is connected to the movable arm 63 of a potentiometer 64, and the other end of which is connected to one end' of the potentiometer 64. The potentiometer 64, in turn, is connected to a pair of power leads 66 and 67 which supply alternating current power to potentiometer 64 as well as to direct current power source 25. v v

4AS has already been indicated, power source 25 is capable of providing a direct current potential between its

terminals

27 and 29, with the terminal 27 being negative and the terminal 29 being positive. In addition, power source provides a further direct current potential between a negative terminal 70 and a positive terminal 71 thereof. This potential between terminals 70 and 71 serves the operation of the electron gun .45. To this effect, the terminal 70 is connected to the gun electrode 51 by a lead 72 which extends through an insulating bushing 713 in housing 46. The terminal 7:1 is connected to the above-mentioned lead 26 which extends to pump housing 10= and also to apertured electrode 52, as shown. The transformer secondary winding 55 has a center tap 7-5 which is connected to the movable arm 76 of a variable resistor 77 which, turn, is connected to lead '72. Varidescription thereof in connection with FIG. 1.

mary,V the source 25 thus provides a first direct current potential between its

terminals

27 and 29, a second direct current potential between itsl terminals 70 and 71, and a third direct current potential between its terminals Si) and 81. Multiple output sources of this type, which include transformers and rectifiers, are conventional and well known.

The current flowing to coil 53 and thus the focussing effect thereof is adjustable by variable resistor 79. The electron beam 78 is focused to impinge on the top surface 83 of getter rod 33. Since the source terminal '71 is positive with respect to terminal 70 and is connected to housing 10, the getter rod 33, through the brackets 35 and the support 34, is biased positively withrespect to gun filament 50 and electrode 51. In this manner, the electrons in beam 78 land easily on the top surface 83 of getter rod 33. This electron impingement causes the getter rod 33 to heat at its top surface and to vaporize getter material therefrom. The electron beam 78 is preferably focused to 'cover a major portion of the top surface 83 of rod 33, so as to prevent the burning of holes into rod 3-3 and provide a substantially uniform vaporization of getter material therefrom.

The getter material vaporized from rod 33 enters the free space defined by pump housing 10 and performs a gas molecule gettering function therein. Particularly, the vaporized getter material deposits itself on the gas molecule collector surface 32 to form a layer of getter material which promotes the entrapment of gas molecules.

While the electron gun 45 is operated, its electron beam 78 vaporizes getter material from the top surface 8-3 of getter rod 33. This top surface will, therefore, successively approach the lower end of rod 33. However, the rod 33, because of its solid configuration and substantial content of getter material, will only be consumed after-many days or months of operation depending on the quantity of gas pumped. The invention, therefore, provides a getter source which is subsident for considerable periods of time, thereby being Vfree of the disadvantages of the prior art structures mentioned above.

In many instances, it may be desirable to have a bar of getter material which presents a large, effective getter vaporization surface. It might be possible in many instances to irradiate such a surface with an electron beam from a large, powerful electron gun. However, FIG. 2 shows apparatus for accomplishing this desideratum with less effort.

Most parts of the pump illustrated in FIG. 2 are the same as those of the pump shown in FIG. 1. These like parts in FIG. 2 have, therefore, been provided with the reference numerals employed for their corresponding parts in FIG. 1. For an understanding of the function of these parts, reference should be Vhad -to the preceding FIG. 2 also does not show most of the electrical equipment, including source 25, transformer 56, potentiometer 64 and variable resistors 77 and 59, illustrated in FIG. 1. This equipment is also used with the pump shown in FIG. `2.

In contrast to the apparatus shown` in FIG. 1, the pump'V illustrated in FIG. 2 has a getter supply which is in the form of an elongated bar of getter material that is positioned to extend at right angles to the longitudinal axis through cylindrical pump housing 10. This fact is best apparent from FIG. 3 which shows a side View of bar 90, together with associa-ted parts. The solid getter bar 90 is held by mounting posts 92 which, in turn, are fastened to supporting brackets 93 that extend from the `inner surface of pump housing 10. The electron beam 78 emanating from gun 45 is focussed -to impinge upon the upper surface 95 of solid getter bar 90. According to this aspect of the invention, the pump shown in FIG. 2 includes a pair of beam defiecting coils 96 and 97 which shown in FIG. 1. The coils 96 and 97 are electrically connected in series and are connected through a variable resistor 99 to a deflection voltage supply 100. The supply 100 furnishes an alternating current which, when `flowing through coils 96 and 97, will cause the electron beam 78 to sweep between the beam positions 78 and 78 indicated in FIG. 3. The variable resistor 99 serves to control the current flowing through coils 96 and 97, and thus the sweep amplitude of the electron beam at bar 90. In the shown embodiment, the coils 96 and 97 are mounted on posts 101 which may be of magnetic material or also of a non-magnetic material, depending on the frequency with which the electron beam is to be sweeped. If desired, the two posts 101 may be magnetically interconnected by a magnet yoke (not shown).

Care should, of course, be taken to keep the electric losses to a` minimum, such as by lamina-ting the magnetic parts.

In this manner, the top surface 95 of bar 90 is substantially uniformly heated to vaporize getter material therefrom. Again, the get-ter bar will be useful for many days or months before replacement thereof becomes necessary. The remaining operation of the pump is the same as that of the apparatus shown in FIG. 1.

FIG. 4 illustrates a further embodiment of the invention. The pump shown in FIG. 4 is similar to that shown in FIG. 1 and has also a housing 10 and an anode grid 24. In addition, it also operates with the electrical supply equipment (not shown in FIG. 4) that has been described and illustrated in connection with FIG. 1. The housing shown in FIG. 4 has a closed bottom 102 and defines an inlet opening 103 for connection to a space or vessel to be evacuated (not shown) at its flange 11. The pump of FIG. 4 also has a solid rod of getter material 33 of the type shown in FIG. 1. This rod 33 is mounted on a base 105 at bottom 102. The housing 10 has a lateral opening 106 provided with a nipple 107 thereat. The nipple 107 has a removable cover 109 sealedto a flange 110 thereof. The cover 109 is similar to the cover disc 39 shown in FIG. 1 and carries also an electron gun of the type of electron gun 45 shown in FIG. l.

lIn FIG. 4, the electron beam 78 emanating from gun 45 travels first along a trajectory that extends at an angle to the longitudinal axis of cylindrical housing 10 and that intersects such longitudinal axis. At this point of intersection, there is provided a permanent magnet 112 which is mounted on housing 10 by a bracket 114. A top view of magnet 112 is shown in FIG. 5. While a C-shaped magnet has been shown, a circular magnet could also be used. Moreover, an electrically energized magnet could be employed in lieu of a permanent magnet. The illustrated permanent magnet 112 has a pair of

pole pieces

116 and 117 which dene an air gap 118 through which the electron beam 78 passes. The magnet 112 is dimensioned and magnetized such that it deflects electron beam 78 onto the top surface 83 of solid getter rod 33. The remaining operation of the pump shown in FIG. 4 is the same as that of the apparatus illustrated in FIG. 1. The structure of FIG. 4 has the advantage that the electron gun can be disposed laterally of the housing 10. While one position for electron gun 45 has been illustrated in FIG. 4, other convenient lateral positions are also possible. If the bulk of getter material is in the form of largediameter rod or a large-area bar, the magnet 112 may be of the electrically energized type having a coil connected to a source of'sweeping voltage. In this case, it would be possible to sweep the electron beam 78 in a manner similar to that illustrated in FIGS. 2 and 3. Moreover, the magnet system illustrated in FIG. 4 may be combined with the deflection magnet system shown in FIG. 2.

FIG. 6 shows a modilication of the embodiment shown in FIG. 4. According to FIG. 6, the getter material rod 33 is heated at its surface 83 by a filament 120, rather than by an electron gun. The filament 120 is mounted adjacent the top surface 83 and above rod 33 and has a pair of

terminals

121 and 122 that extend through insulation bushings 1'24 and 125 to the outside of housing 10 to be connected to a filament heating source 127. A high voltage source 128 biases filament 120 negatively with respect to getter material rod 33. The bottom 102 of housing 10 defines an opening 130 and has a hermetical bellows 131 mounted thereat. Bellows 131 has a bottom 132 from which there extends a supporting strut 133 for getter rod 33. A threaded bolt 135 is welded to and extends from the lower surface of bottom 132. The bolt 135 extends through an opening of a yoke 136 that is mounted on housing bottom 192. A nut 138 sits on bolt 135 and bears against yoke 136. The distance between the top surface 83A of getter rod 33 and the filament ,120 can be adjusted by actuating nut 138. This distance is initially adjusted so that the electrons released by heated filament 120 and attracted by positively biased getter rod 33 produce a desired vaporization of getter material on the top surface 83 of getter rod 33. As the rod 33 wears down due to vaporization of getter material therefrom, the nut 138 is manipulated from time to time to maintain the proper distance between rod top surface 83 and lament 120. Again, the getter supply will be operative for many hours or days, before replacement of the getter rod 33 will become necessary. The ion pump system of the apparatus shown in FIG. 6 comprises a cylindrical anode grip 24 of the type mentioned above. The necessary high voltage between the inner surface 32 of housing 10 is applied by an ionizing voltage source 140 the negative terminal of which is connected to pump housing 10. The positive terminal of source 140 is connected to anode 24 through an insulating bushing 141. The function of the pump shown in FIG. 6, as far as the ionization of gas molecules and the operation of vaporized getter material is concerned, is the same as that described in connection with the preceding figures.

Many modifications of the shown embodiments within the scope of the invention will become apparent to those skilled in the art. Thus, other types of getter-ion pump systems than those shown may be used in conjunction with the invention.

I claim:

1. A getter-ion pump, comprising a pump housing, means for ionizing gas molecules in the pump housing and for entrapping the ionized gas molecules on a molecule collecting surface in the pump housing, a solid bar of getter material in the pump housing, an electron gun for releasing an electron beam into the pump housing, means for focussing the electron beam onto a surface of said solid bar, and means for continuously detlecting the electron beam within the extent of said surface to cause the electron beam to travel over said surface and vaporize getter material from said solid bar into the pump housing and onto the molecule collecting surface.

2. A getter-ion pump, comprising a pump housing, means for ionizing gas molecules in the pump housing and for entrapping the ionized gas molecules on a molecule collecting surface in the pump housing, a solid bar of getter material in the pump housing, an electron gun for releasing an electron beam into the pump housing, and a magnet structure for deflecting the electron beam onto said solid bar to cause release of vaporized getter material into the pump housing and onto the molecule collecting surface.

3. A getter-ion pump, comprising a pump housing, means for ionizing gas molecules in the pump housing and forentrapping the ionized gas molecules on a molecule collecting surface in the pump housing, a solid bar of getter material in the pump housing, an electron gun for releasing an electron beam into the pump housing, and a permanent magnet structure for deecting the electron beam onto said solid bar to cause release of vaporized getter material into the pump housing and onto the molecule collecting surface.

4, A getter-ion pump, comprising a substantially cylindrical pump housing having a longitudinal axis, means for ionizing gas molecules in the pump housing, a solid bar of getter material located in the pump housing on the longitudinal axis thereof, an electron gun for sending an electron beam along a trajectory extending at an angle to and intersecting the longitudinal axis of the pump housing, and a magnet structure at and about the point of intersection of the electron beam trajectory and the longitudinal housing axis for deflecting the electron beam onto the longitudinal housing axis and onto a surface of said Y solid bar to cause release of vaporized getter material from said solid bar and into the pump housing and onto the molecule collecting surface.

5. A getter-ion pump, comprising a pump housing, means for ionizing gas molecules in the pump housing and for entrapping the ionized gas molecules on a molecule collecting surface in the pump housing, a solid bar of getter material extending along part of a vertical axis through the pump housing and having a substantially References Cited by the Examiner UNITED STATES PATENTS 2,771,568 11/1956 Steigerwald 11S-49.5 X 2,850,225 9/1958 Herb 230--69 3,024,965 3/ 1962 Milleron 230-69 3,074,621 1/1963 Lorenz et al. 230-69 3,162,767 12/1964 Di Curcio et al. ll7-l07 X MARK NEWMAN, Primary Examiner'.

DONLEY J. STOCKING, Examiner.

W. E. COLEMAN, Assistant Examiner.

Claims

1. A GETTER-ION PUMP, COMPRISING A PUMP HOUSING, MEANS FOR IONIZING GAS MOLECULES IN THE PUMP HOUSING AND FOR ENTRAPPING THE IONIZED GAS MOLECULES ON A MOLECULE COLLECTING SURFACE IN THE PUMP HOUSING, A SOLID BAR OF GETTER MATERIAL IN THE PUMP HOUSING, AN ELECTRON GUN FOR RELEASING AN ELECTRON BEAM INTO THE PUMP HOUSING, MEANS FOR FOCUSSING THE ELECTRON BEAM ONTO A SURFACE OF