US3172597A - Ionic pump - Google Patents

Description

United States Patent O 3,172,597 IGNIC PUMP Lucien Guyot, Paris, France, assignor to Compagnie Francaise Thomson-Houston, Paris, France Filed July 5, 1961, Ser. No. 122,067 Claims priority, application France, .luly 8, 1960, 832,470 8 Claims. (Cl. 23u- 69) The present invention relates to an ionic pump of the getter type with a self-actuated discharge in a magnetic field and having the advantages of negligible outer magnetic field, reduced size and very light weight.

It is known that in certain ionic pumps of the getter type, such as those described in U.S. Patent No. 2,755,014 filed April 24, 1953, an autonomous ionic discharge known as the Penning discharge is used, said discharge being produced in non-parallel electrical and magnetic fields. According to a preferred embodiment, the ionization chamber of such a pump contains a positive electrode in the shape of a hollow cylinder and two negative electrodes made of a material, such as titanium or carbon which absorbs gaseous ions. These two electrodes are oppositely arranged at the open ends of the positive electrode. This system is located in a magnetic field parallel to the axis of the cylinder and produced by a magnet arranged outside the enclosed space containing the system. When an ionic discharge takes place between these electrodes, the electrons produced can only reach the positive electrode along very long helical paths. Thus the likelihood of ionizing shocks is increased to the point at which the discharge is maintained at extremely low pressures. The ions produced travel towards the negative electrodes which absorb them.

These pumps, which require no other means of operation than a high voltage supply, are very suitable to remain sealed permanently to electronic tubes in which it is desired to maintain a high vacuum. However, up to now they could not be associated with tubes using precision electron optical systems, and more particularly those in which low speed electrons are encountered, such as camera tubes and image tubes. In fact, these pumps have a considerable outer magnetic eld which introduces intolerable defects into the electron optics. In principle it is possible to have an effective magnetic screening either of the pump or of the electronic tube, but this increases the volume and the Weight of the assembly to a prohibitive extent, in particular in the very frequent cases in which the electronic tube is fragile and in which furthermore it must operate in transportable devices.

The present invention has for an object to provide an ionic pump of the getter type with a magnetic field which, whilst having a small volume and -a light weight, has hardly any outer magnetic lield. The principle of the invention consists in reducing the outer eld by means of a compensating magnetic structure.

The present invention provides an ionic pump of the getter type using an ionization chamber, in which there prevails a magnetic field, having the following arrangements:

The ionization chamber is essentially constituted by a hollow cylinder of a non-ferromagnetic material connected on either side to ferromagnetic plates. It is surrounded by a magnet in the shape of a hollow cylinder magnetized in the direction of its axis and magnetically connected to the two ferromagnetic plates. Outside the chamber and coaxial with it, is arranged a second magnet, a so-called compensation magnet, preferably of identical shape to the first, magnetized in the opposite direction to that of the first and magnetically connected by one of its polar faces to one of the two plates of the chamber and by the other to a third ferromagnetic plate.

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According to a preferred embodiment, the assembly is surrounded by a magnetic screen in the form of `a box, two opposite walls of which are magnetically connected respectively to the two end plates of the assembly, each of the plates being capable of constituting one of the walls of the box.

The term magnetically connected, as applied to these elements of the magnet circuit indicates, according to common usage, any arrangement for which the reluctance between these elements is very small in relation to the total reluctance of lthe circuit. The magnetically connected elements can therefore be either in immediate contact, or integral with one another, but may also be separated by a fairly narrow gap or connected by means of a third ferromagnetic element.

The invention will now be further described with reference to the accompanying drawings, in which:

FIGURE 1 illustrates a non-compensated structure,

FIGURE 2 illustrates the principle according to this invention,

FIGURE 3 illustrates one construction of ionic pump according to this invention, and

FIGURE 4 illustrates an embodiment comprising two ionic pumps.

The pump which is the object of the invention, even in its most simple form, i.e. without screening, has a very small leakage eld. In fact, its magnetic structure is approximately symmetrical in relation to a plane. The external fields produced by each half thus practically compensate for each other at a certain distance from the structure. For this reason, lthe screening which is used in the preferred embodiment can have reduced dimensions and its walls can be thin.

Another advantage of this pump arises from the fact that the compensation magnet, while weakening the leakage eld, reinforces the ield in the useful area of the pump. This effect will be illustrated by FIGURES 1 and 2, wherein FIGURE 1 diagrammatically shows the induction spectrum for a non-compensated structure and FIGURE 2 shows that found in a structure according to the invention. It may be seen that in the first case the magnetV 1 produces a ux the parasitic component of which, corresponding to the induction lines 2, is comparable to the useful component 3. This latter stems from the large extent of the polar faces, one of which is constituted by one whole side of the plate 4 and the other by the inner surface of the screening box 5 connected to the plate 6.

This is no longer the case in the structure according to the invention and diagrammatically shown in FIG- URE 2. In this iigure, a second magnet 7 magnetized in the opposite direction to that of 1, is connected on the one hand to the outer surface of the plate 4 andon the other hand to an inner surface of the screening box 5. The parasitic flux is very reduced because the para- -sitic induction lines can only originate in the half situated towards the magnet 1 of the circumferential zone of the plate 4. In fact no induction line produced by the magnet 1 can pass through the plane of symmetry 9 of the structure. The lessening in the parasitic flux results in an advantageous reinforcement of the useful induction, allowing the volume of the pump to be reduced and thus facilitating its use on fragile electronic tubes.

The invention preferably applies to the ionic pumps of the type shown in U.S. Patent No. 2,755,014. In this case each of the two ferromagnetic plates supports an electrode made of a material which absorbs the ions of the gas to be pumped whilst a third electrode of annular shape taken to a positive potential in relation to the two previous ones is arranged in the space between the latter coaxially in relation to the line connecting them.

Ving into the chamber 1.

surface of the plate 14.

But the invention is not limited to these types of pumps and it may be applied to any system of ionic absorption pumpsythe ionization chamber offwhich is subjected to a magnetic field.

FIGUREy 3-diagrammatically shows an embodiment ofthe ionic pump which is the object of the invention.

The pump in FIGURE 3 is made-up of a discharge structure contained in an ionization chamber-10 vand of an outer structure 11 co-operating with the members of the chamber 16 in order to create a magnetic field limited to the chamber' 10. This chamber-is constituted by a glass cylinder 12 sealed to two-plates 13,v 14 of ferromagnetic material, for example rKovar. The plateV 13, which has a greater diameter than 14, comprises a gas inlet port 15. A glass pipe 16 `sealed tothe plate 13 connects the pump to the electronic tube to be pumped. These plates 13 and 14 have projections 17, 18' extend- The projections 17, 18 are covered with sheets 19, 20 of a material such as carbon or titanium which can absorb the gases in fthe ionized state. These sheets are intended toconstitute the negative electrodes of a Penning discharge, the positivey electrode being constituted -byV a hollow cylinder 21 arranged the walls 27 comprises an opening into which islocated the plate 13, whilst-the opposite wall 28 comes into contact with the magnet 25. Finally the cylindrical ' members 29, 30 of ferromagnetic materiaL-similar to the members 17, 18 are fixedwithin the axis of the structure on to the inner surface-ofthe Wall 28 and on to the outer In this 'pump'the plate 14 is magnetically connected to the polar faces ofthe two mag- Ynets 23 and 25 by means of the ferromagnetic ring 24,

and the wall 28 of the box 26 forms the ferromagnetic plate connected, according -to-the invention, to the lend of the compensation magnet 25. The induction fiuxoband the two adjacent ferromagnetic plates at-:itsends can enclose the ionization chamber f a second pump cooperating with'the first.

(b) In pumps containing-a single yactive structure, the compensation magnet can be constituted by a solid cylinder arranged on the axis offthe pump.

(c) The discharge electrode orelectrodes of the pump can be directlyv fed `bythe current conductors `of the velectronic tube to be pumped, the connecting conductor being inside the vacuum enclosure.

FIGURE 4- fshows an embodiment comprising two ionic pumps 4and vhaving two ionizationrchambere'as `described in paragraph (a) above.

Certain elements of this latter embodiment, referenced 16 to 30, have substantially the same functions as those elementsbearing the numbers corresponding references in FIGURE 3. In addition, the embodiment of FG- URE 4 comprises the following parts:

A second glass cylinder 31, constituting with the elements 12, 13, 14, 28 the vacuum-tight enclosure.

A second hollow cylinder 32 constituting `the positive electrode of the second ionization chamber.

An electrical conductor 33 connecting the electrode 32 to the electrode 21 through an aperture 34 in the ferromagnetic plate 14.

Sheets 35 and 37 of a material absorbing gases in the ionized state, just like the sheets 19 and 20. These sheets 36 randy 37 cover the ferromagnetic cylindrical elements and constitute the negative electrodes of the second ionization chamber.

It is clear that for constructional reasons the casing 26 cannot form a single part with the plate 2S, as is .the

vcase in FIGURE 3, but these two elements are magnetically connected as hereinbefore explained. TheV plate 23 is separated from the box 26 by the spacing shown at 35. The magnetic 'connection between the plate 28 and the magnet 25 is therefore ensured.

I claim:

1. An ionic pump of the getter type having an ionization space which is subjected to a magnetic field, comprising a hollow cylinder of non-ferromagnetic material defining the ionization space, a first ferromagnetic member arranged at one end of the hollow cylinder, a second .ferromagnetic member arranged at the other end of said hollow cylinder, at least one of .said ferromagnetic members supporting an electrode of ion absorbing `material on its surfacefacing the interior of the hollow cylinder, an annular Velectrode within the hollow cylinder arranged between the rfirst and the second ferromagnetic members and having'its open ends directed towards these members and adapted to be carried to a positive potential with respect to these members, an aperture in one of said ferromagnetic members forming an inlet for the gas to be pumped, a supply conductor to said annular electrode extendingthrough said aperture, a first magnet in the form of a hollow cylinder magnetized in the axial direction which surrounds vsaid hollow cylinder and is magnetically connected tothe rst and the Vsecond ferromagnetic members, a second magnet arranged Aoutside the assembly formed by said first magnet and the first and the second ferromagnetic members coaxially therewith and acting as a compensation magnet which is magnetically connected by one of its polar faces to the second ferromagnetic member and magnetized in the opposite direction to kthe .first magnet, and a third ferromagnetic member magnetically connected to the Vother polar face of the second magnet.

2. A pump as claimed in claim 1, comprising a surrounding magnetic screening structure in the form of a box magnetically connected to the first and third ferromagnetic members.

3.'A pump as claimed in claim 2 in whichthe third ferromagnetic member constitutes one of the walls `of the box.

4. Apump as claimed in claim 1, including a second ionic pump .structure co-operating with the first ionic pump and arranged between the second .and third ferromagnetic members, said second pump structure also comprising a hollow cylinder of non-ferromagnetic material defining the ionization space and extending between said second and third ferromagnetic members, an electrode of ion absorbing material supported by at least one of said second and third ferromagnetic members and facing the interior ofthe. hollow cylinder, an annular electrode within the hollow cylinder having its ends directed towards said second and third ferromagnetic members, ,an `aperture in said second ferromagnetic member forming an inlet for the gas to be pumped and providing communica- `tion between the ionizationspaces of the two pumps, a

supply conductor for connecting said annular electrode to a positive potential extending through said aperture and connecting with the supply conductor to the annular electrode of the first pump, and said second pump structure being surrounded by said second magnet.

5. A pump as claimed in claim 1, in which the second magnet is similar to the first magnet.

6. A pump as claimed in claim l, in which the second magnet is constituted by a hollow cylinder.

7. In an ionic pump comprising a member of nonferromagnetic material defining an ionisation chamber containing members of ion absorbing material and surrounded by a magnet structure producing a magnetic field directed axially of the chamber, the improvement which comprises arranging compensating magnet means which are magnetized in the opposite direction to the magnet structure externally of said chamber in order to reduce the magnetic lield produced outside said chamber.

8. In an ionic pump comprising a member of nonierromagnetic material defining an ionisation chamber containing two spaced members of ion absorbing material and an annular electrode arranged between said two members which is adapted to be carried to a positive potential and wherein a magnet structure is arranged around said chamber to produce a magnetic lield extending axially of said chamber and said annular electrode, the improvement which comprises arranging compensating magnet means which are magnetised in the opposite direction to said magnet structure externally of said chamber in order to substantially reduce the magnetic field produced outside said chamber.

References Cited in the le of this patent UNITED STATES PATENTS

Claims (1)

1. AN IONIC PUMP OF THE GETTER TYPE HAVING AN IONIZATION SPACE WHICH IS SUBJECTED TO A MAGNETIC FIELD, COMPRISING A HOLLOW CYLINDER OF NON-FERROMAGNETIC MATERIAL DEFINING THE IONIZATION SPACE, A FIRST FERROMAGNETIC MEMBER ARRANGED AT ONE OF THE HOLLOW CYLINDER, A SECOND FERROMAGNETIC MEMBER ARRANGED AT THE OTHER END OF SAID HOLLOW CYLINDER, AT LEAST ONE OF SAID FERROMAGNETIC MEMBERS SUPPORTING AN ELECTRODE OF ION ABSORBING MATERIAL ON ITS SURFACE FACING THE INTERIOR OF THE HOLLOW CYLINDER, AN ANNULAR ELECTRODE WITHIN THE HOLLOW CYLINDER ARRANGED BETWEEN THE FIRST AND THE SECOND FERROMAGNETIC MEMBERS AND HAVING ITS OPEN ENDS DIRECTED TOWARDS THESE MEMBERS AND ADAPTED TO BE CARRIED TO A POSITIVE POTENTIAL WITH RESPECT TO THESE MEMBERS, AN APERTURE IN ONE OF SAID FERROMAGNETIC MEMBERS FORMING AN INLET FOR THE GAS TO BE PUMPED, A SUPPLY CONDUCTOR TO SAID ANNULAR ELEC-

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