US3603703A - One- or multisteps compressing ionic pump - Google Patents

Abstract

A one- or multisteps compressing ionic-pump which comprises means for providing a chamber of higher pressure and a chamber of lower pressure, and a separating wall nonpermeable to gas is disposed between the chambers. At least one channel member extends through the wall for the transportation of an ion stream therethrough. The channel member has a large stream resistance for the gas return-diffusing from the area of higher pressure into the area of lower pressure, and a high frequency alternating field is applied in front of the entrance to the channel member in the lower pressure chamber between an anode preset in front of the separating wall and in and behind the channel member in higher pressure chamber connected cathodes, so that particles of gas do not arrive at lower pressure in the space.

Description

Erich Jaltopic Steyrergasse 17/llll, Graz, Austria [21] Appl. No. 811,960

[22] Filed Apr. 1,1969

[45] Patented Sept. 7, 1971 [72] Inventor [54] UNlE- 0R MULTISTEPS COMPRESSING EONHQ [56] References Cited UNITED STATES PATENTS 2,880,373 3/1959 Soloway 315/108 230/69 3,169,693 2/1965 Herzog Primary Examiner-Robert M. Walker Attorney-Ernest G. Montague ABSTRACT: A oneor multisteps compressing ionic-pump which comprises means for providing a chamber of higher pressure and a chamber of lower pressure, and a separating wall nonpermeable to gas is disposed between the chambers. At least one channel member extends through the wall for the transportation of an ion stream therethrough. The channel member has a large stream resistance for the gas return-diffusing from the area of higher pressure into the area of lower pressure, and a high frequency alternating field is applied in front of the entrance to the channel member in the lower pres sure chamber between an anode preset in front of the separating wall and in and behind the channel member in higher pres sure chamber connected cathodes, so that particles of gas do not arrive at lower pressure in the space.

one on Murrrsrnrs coMrnnss'iNc ionic PUMP The present invention relates to a one or multistep compressing ionic pump.

For the production of a high vacuum, in addition to propellant pumps (injector pumps and diffusion pumps), molecular pumps and pumps which suck up the permanent gases and vapors by means of condensation at corresponding lower temperature (by example Kryo pumps), and also the so-called ionic pumps.

In accordance with an organization principle, one distinguishes between compressing and noncompressing pumps. Compressing vacuum pumps bring about by means of one or a plurality of compressing steps a pump effect, while in case of noncompressing pumps, the gas particles to be removed condense on a solid wall or are bound physically or chemically by other means.

Also in ionic pumps, these two groups can be distinguished: The pumps of the second-mentioned type, the so-called ionic pumps, which are divided depending upon the principles and means to be used in ionic-getter evaporation pumps and ionicgetter diffusion pumps, obtain the pump effect by ionization of the gas and vapor-molecules and transportation of these ions by means of electromagnetic fields to solid walls, to which they are physically or chemically bound.

In compressing ionic pumps, however, the ionic stream which determines the sucked-off gas quantity is transported by means of electromagnetic fields into areas of higher pressure. The difference in pressure is brought about due to a difference in the ionic stream and of the return diffusion stream from the area of higher pressure. In order that a pressure difference is brought about at all, the ionic stream must be greater than the gas stream diffusing into the area of lower pressure. The first compressing ionic pump originates from R. Champeix (Compt. rend. acad. sci. July 3, 1950, see also R. Champeix, Physics and Techniques of Electron Tubes, Vol. I, Principles of Vacuum Technique, Pergamon-Press 1961, p. 129 f.) and another from H. Schwarz (Le vide, No. 42, p. 1263, 1952, see also M. Pirani and J. Yarwood, Principles of Vacuum Engineering, Chapman & Hall, p. 292 ff. and Champeix, a.a.0. p. 129).

It is an object of the present invention to provide an ion pump comprising a housing having a first connection adapted to be connected to a vessel to be pumped and a second connection adapted to be connected to a wort pump, a glowing electron source disposed in the housing, a separating wall dividing the housing into a lower pressure chamber and a higher pressure chamber, a channel member disposed in the separating wall, an anode catching electrons becoming free from the electron source, and cathodes connected in the higher pressure chamber. The electrons produce ions from gas from the vessel to be pumped, the channel member being permeable for the ions and substantially nonpermeable for return diffusing gas, whereby the ions are drawn in and by means of the channel member are led in the direction of the wort pump. A positive auxiliary electrode is disposed in front of the connection for the vessel to be pumped, which auxiliary electrode prevents a return diffusing of the ions into the vessel to be pumped. An anode is preset in front of the separating wall, and a high frequency alternating field is applied in front of the entrance to the channel member in the lower pressure chamber between the preset anode and in and behind the channel member in the higher pressure chamber connected cathodes so that particles of the gas do not arrive at lower pressure in the space.

It is another object of the present invention to provide an ion pump as above wherein the high frequency alternating field is connected at the channel member, so that the particles of the gas which are already in the channel member are ionized and guided back.

With these and other objects in view which will become ap parent in the following detailed description, the present invention will be clearly understood in connection with the accompanying drawing, in which:

FIG. l is a schematic elevation in section of the Schwarz P p FIG. 2 is a schematic showing of an ionic pump designed in accordance with the present invention;

FIG. 3 is an embodiment of a one-step arrangement with high frequency; and

FIG. 4 is a schematic showing of the application of a highfrequency alternating voltage.

Referring now to the drawing, the pump of Schwarz is shown schematically in FIG. 1. The pump comprises a glow electron source F, an anode A, a repulsion electrode lit, negatively charged auxiliary electrodes (1 and positively charged auxiliary electrodes G (ring electrodes). In the direction ii is disposed the connection to the vessel to be pumped, while in the direction V the wort pump is connected. The electrons emitted from the electron source K" are attracted by the anode A and ionize along on their path the gas particles by a magnetic field operating in the direction of the vessel axis, in addi tion to the movement in screw paths. The repulsion electrode 1R forces the electrons to return, whereby the ionization expectation is increased. The produced ions are attracted by the negative electrodes C, pass therethrough, and are sucked off by a wort pump. The electrode G prevents the ions from a return into the high vacuum space or chamber. With this pump, Schwarz obtained a suction speed of several liters/sec. at a pressure between l.33-l0 'l.3l3'l0 mbar., as well as a limit vacuum of about I.3 l0 mbar.

A pump having a greater output has been constructed by Foster, Lawrence & Lofgren (Rev. Sci. Instr. 24, 388, 1953), see thereto for example also M. Pirani & J. Yarwood p. 294 if.

It obtains a suction speed of 3000-6000 liters/sec. at a pressure of (1-6). 10 mbar., requires, however, a power input of totally 36.5 kw. (oil diffusion pumps with about the same suc tion output have a power requirement of 4 to 5 kilowatt).

The first named pump of R. Champeix has a suction speed of 18 liters/sec.

The mentioned and similar arrangements have the draw backs of slow suction output and/or low limit vacuum and enormous power input for obtaining greater suction output, respectively.

These drawbacks are the consequence of the appreciable return diffusion of the electrically neutral gas particles from the area of higher into the area of lower pressure, caused by the great passage cross section for the gas particles within the pressure steps.

It is one object of the present invention to provide a one or multistep compressing ionic pump which avoids the draw/-- backs of the known structures.

It is another object of the present invention to provide a one or multistep compressing ionic pump, wherein the area of higher pressure is separated from the area of lower pressure within one pressure step by arrangement of a wall nonpenetrable by the gas, in which for the transportation of the ionic stream, one channel or a plurality of parallel channels having greater flow resistance are arranged (FIG. 2). A and E identify the areas of lower and higher pressure P, and P respectively. A wall W is arranged which separates the two areas, and a channel if is provided which leads the ionic stream from A to 0. For instance, if it is formed as a tube having circular cross section, it has a diameter d. and a length 1. Furthermore, the suction speed S, and S is indicated in the areas A. and E3), respectively.

If ii is the ionic current flowing through the channel from A to B, then the following equation applies:

i I 1 sz 2-4-10 +(1- )L whereby S is the suction speed in A in liter/sec. S is the suction speed in B in liter/sec. p is the pressure in E in mbar. p is the pressure in ii in mbar.

1 is the ion current in mA L is the feeding value of the channel in liters/sec.

The given formulas are valid for the area of the molecular stream, whereby as a condition is given p.d 1.3310.

If one has instead of a channel only an opening in the wall (diaphragm), the cross section amounts lF cmF, it is necessary to substitute for L in the above stated formulas the factor 12.1 F.

An example will demonstrate the progress obtained with the method of the present invention.

If it is assumed that with one pressure step a pressure reduction of 10 mbar. to 10 mbar. is to be achieved, thus P,=l mbar. and P ==l0 mbar. thus also 10 X r.l l.3l3-l0 for A and l()'-a l.33-1O for l3 thus dl.33 cm. for A and d l.33 cm. for it, it is thus d l .33 cm. to be made.

We choose a channel with (1 0.2 cm, and a length of i=2 cm. In accordance with a known formula L becomes now L--l2'( laF/l )f, whereby fits the Qlausiug factor function of (d/ l tllt).

One obtains from a table curve (see M. Wutz, Theorie and Praxis der Vakuumtechnik, Vicweg 1965, p. 1 1-4) for this ratio a Clausing factor off-0.9. One obtains thereby Ll2.1 (0.2 /2-0.9=-O.0435 liters/sec. A diaphragm of the same diameter has an area of 0.0435 cm? and thus a value of L of 0.53 liters/sec; thus channel 2 z: 0082 L I diaphragm 0.53 the channel feeds thus fi =12 times worse than the diaphragm With an ionic current of ma; one obtains now in A a suction speed of In case of the diaphragm S1 2.4--9.0.53=2.4-4.75==2.35, the return stream thus being three times greater than the ionic stream. One would have to make the ionic stream I appreciably larger than 10 ma.

It is understood that the opening in the wall (diaphragm) is to be considered as limit of the method of the present invention, in which thus the relationship (Ii/d) moves towards O. (Practically due to the always finite wall thickness is this ratio different from zero).

The form ofthe channel is to be selected in accordance with the statement above, if it has only a sufficiently large stream resistance. in addition to the mentioned cylindrically shaped channel, as a matter of course, also slot-shaped channels with a curved axis and the like can be used.

The production of the ionic current takes place in known manner for instance, by illuminous discharge, high-frequency discharge. Penning discharge, by electron discharge by means ofa glowing cathode or by arch discharge. An embodiment by example by a one-step arrangement with high frequency is shown in FIG. 3. The arrangement comprises a recipient R, a

high frequency electrode ii), an ionic channel K, electrodes 0, b, c, d, e. The gas ionized in the space between A and B is sucked off by the extraction system K, c, d, e, and compressed in the space 151, from which it is sucked ofi by a wort pump.

The channel of the extraction system is conically shaped relative to the bundle of the ions. By this arrangement, a concentration of the current and thereby an appreciable incr a a of the current flow through the channel is brought about. it to be understood that also other focusing arrangements can ,e arranged for the concentration of the ionic current. In principle, they work all as electromagnetic lenses for the ion raysv A further reduction of the return diffusion can be obtained by at least partly ionizing again the electrically neutral gas particles retum diffused from A to E5 in the channel, whereby they are forced to reverse due to 2. simultaneously applied, for nstance, el ctrical field. Tl c ioni" tion in the channel can t l frequ icy alternating voltage HG. -iscrcse 1 several embodiments of the invention, it is to he understood that these embodiments given by example only and not in a limiting sense.

I claim:

H. An ion pump, comprising a housing having a first connection adapted to be connected to a vessel to be pumped and a second connection adapted to be connected to a wort pump,

a glowing electron source disposed in said housing,

a separating wall dividing said housing into a lower pressure chamber and a higher pressure chamber,

a channel means disposed in said separating wall,

an anode catching electrons becoming free from said electron source, and

cathodes connected to said higher pressure chamber,

said electrons producing ions from gas from said vessel to be pumped,

said channel means being permeable for said ions and substantially nonpermeable for return diffusing gas,

said ions being drawn in and by means of said channel means being led in the direction ofsaitl wort pump,

a positive auxiliary electrode disposed in front of said first connection for said vessel to be pumped, which auxiliary electrode prevents a return diffusing of said ions into said vessel to be pumped,

an anode preset in front of said separating wall, and

a high frequency alternating field applied in front of the entrance to said channel means in. said lower pressure chamber between said preset anode and in and behind said channel means in said higher pressure chamber-connected cathodes so that particles ofsaid gas do not enter a lower pressure in the space.

2. The ion pump, as set forth in claim I, wherein said high frequency alternating field is connected at said channel means, so that said particles of said gas which are already in said channel means are ionized and guided back.

ior. pump, as set forth in claim 2, wherein said ch..nnel means in part is conically shaped relative to the path ofsaid. ions.

1. The ion pump, forth in claim 3, wherein said high freq cy alternating field is connected at one end to said coni ally shaped part of said channel means and to the other end of said channel means.

Claims (4)

1. An ion pump, comprising a housing having a first connection adapted to be connected to a vessel to be pumped and a second connection adapted to be connected to a wort pump, a glowing electron source disposed in said housing, a separating wall dividing said housing into a lower pressure chamber and a higher pressure chamber, a channel means disposed in said separating wall, an anode catching electrons becoming free from said electron source, and cathodes connected to said higher pressure chamber, said electrons producing ions from gas from said vessel to be pumped, said channel means being permeable for said ions and substantially nonpermeable for return diffusing gas, said ions being drawn in and by means of said channel means being led in the direction of said wort pump, a positive auxiliary electrode disposed in front of said first connection for said vessel to be pumped, which auxiliary electrode prevents a return diffusing of said ions into said vessel to be pumped, an anode preset in front of said separating wall, and a high frequency alternating field applied in front of the entrance to said channel means in said lower pressure chamber between said preset anode and in and behind said channel means in said higher pressure chamber-connected cathodes so that particles of said gas do not enter a lower pressure in the space.

2. The ion pump, as set forth in claim 1, wherein said high frequency alternating field is connected at said channel means, so that said particles of said gas which are already in said channel means are ionized and guided back.

3. The ion pump, as set forth in claim 2, wherein said channel means in part is conically shaped relative to the path of said ions.

4. The ion pump, as set forth in claim 3, wherein said high frequency alternating field is connected at one end to said conically shaped part of said channel means and to the other end of said channel means.

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