DE1539143A1 - Getter vacuum pump - Google Patents

Description

Priority: 2 ?. Aug. 1964 - United States v. America Ser. Ho. 592.417

The invention relates to vacuum pumps of the getter type and .in particular a "novel sublimation device for use in such pumps.

It has been known for many years to use thermal evaporation or sublimation of getter material to pump onto the inner walls of a correspondingly pre-pumped pump housing. ^: Gas molecules that come into contact with it combine chemically or physically with the condensed material and are removed from the gaseous state, so that the pressure is reduced. When using pumps of this type, extremely high pumping speeds are achieved, more than 3 * 500 l / aec. for the active gases such as 0 '., ^1T,' CO and C0_, which can be increased,

C. C. C.

if that is desired. Such devices can not be used to

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Pumping out Her noble gases are used "in combination with-an ion or diffusion vacuum pump that pumps out the Ή del gas" and 'other inactive gases' to a certain extent-but there is still one ^ is more practical and useful pump. "■ ■ - ^ '■■■ ·;% .-''.:

So far bestarid'die "Sublimatioiiseinric'htung usually on / off, a wire, a hochschmöIzenden Me'täll '(for example, a heat-resistant metal such as V / orrfam barren tantalum) in'Form one ^S;! Tabes, a Mnzel- - · dratites or a rope ', and- a coating- or-

öpule, 'which originally had a good thermal' connection 'with it and consisted of a metal whose sublimation temperature is lower than the melting point of the wire and which has good getter properties (for example a reactive' Me ^-taii; iii "e '-. * ■ ^fI titanium or zirconium) The getter was from the' wire worn ^ 'and ^Y befäin'd -öreh originally in'gut thermally conductive Berühruhg with ^{de'm'Drähf'auf:"} · ^"; the full-length" · voltage wurd'e on Sublimationseinrfohtung 'aarfn'eine-' put through the through flowing current resulted in a warming. "until a 'temperature erreichi; was, 'bei' deo * äi & ä ^: Ge'tt ^: er * m'a'terial sublifflierte '. "* ''" - ■■ - ■ ..: _..-.... ■: - ■■ ·.-.- ^: · λ.-; ..... ·., .. · .... ■ ........

As soon as 'the sublimation device was switched on', it surrendered a Strdmfius's both in the wire and in the getfermatefial. The temperature was usually reasonably constant in time, 'so that a 'constant rate of sublimation'. However, it has been observed that they are after some time a small area (hot spot) "of the sublimation unit" when the temperature reached its highest value. The evaporation rate in this area was accordingly larger than at any other place * in the sublimation facility.

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The "vitte ^ SQhnitt. of the getter material decreased, and the ho.tspot area. , was opposite the rest of the sublimation facility even hotter: The evaporation rate rose three-fold, until there was no getter material at the hot spot.

The current then only flowed through the wire, and this current was usually too small to generate the heat required to sublimate the remaining getter material. An attempt to increase the current through the wire by increasing the voltage usually resulted in a burn through of the wire so that 50 % to 60 % of the getter material could not be consumed.

The invention is therefore intended to provide an improved sublimation device are made available, for example in getter vacuum pumps can be used and in which a larger percentage of the getter material "can be used up".

According to the invention, a sublimation device is therefore available made, which consists of a heat-resistant wire, on which one stranded layer is wound, which is in direct thermally conductive contact with it. The layer consists of at least two wires of getter material and a single wire made of a heat-resistant metal, the melting point of which is higher than the sublimation temperature of the getter material. The first mentioned or core wire is preferably a cylindrical core, for example made of tungsten, with a diameter d. The layer preferably consists of two, if desired also more wires made of getter material, for example titanium, with a diameter in the order of magnitude of d or something

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larger than d, and a single wire made of heat-resistant metal, For example molybdenum, with a diameter smaller than d », preferably in the order of magnitude of d / 2.

An essential feature of the invention is that the sublimation device consists of a heat-resistant wire onto which a multi-stranded layer is wound in direct, thermally conductive contact which consists of two or more wires of getter material and a single wire of a hita-resistant metal.

The relative dimensions in the case of the invention are also of importance Sublimation direction, namely that with a core wire with a diameter d, the getter material wires have a diameter in the Of the order of d or slightly larger than d, and the single wire of heat-resistant metal a diameter smaller than d has, preferably d / 2.

In a further embodiment of the invention, the core wire is preferably made '' made of tungsten, the getter material made of titanium and the single wire Molybdenum.

The invention will be explained in more detail with reference to the drawing; show it"

Fig. 1 is a partially cut-away view of a sublimation cartridge '

with the sublimation device according to the invention} and FIG. 2 shows an enlarged partial view along the line 2-2 in FIG.

In Fig. 1, a sublimation cartridge 10 is shown in which the

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Invention-agemäsäe SuMiiüationseinrio ^ itung 11 used i «t. The pa- '"' trone IO contains several sublimation devices 11, which individually '/ · ■ ·' can be excited when one is consumed. These sublimation messages 11; each detachable at one end to hetail rod leads 12 with a screw terminal 13 and at the other end with a single screw terminal 14 held, the ah; a rod 15 is seated. A Loosening and retightening these screws is all that is needed to replace them a sublimation device 11 is required. One with Spacer plate 16 provided with openings prevents a short circuit of the sublimation devices 11. The support rod 15 and the supply rods 12 sit in an all-metal vacuum sealing flange 17 and lead through this in a vacuum-tight manner. The lead rods 12 are with ceramic insulators 18 electrically insulated against the flange if, the vacuum-tight to the supply rods 12 on the one hand and the flange 17 ' on the other hand are soldered. The flange I7 is designed so that it is vacuum-tight with another all-metal vacuum sealing flange 19 fits together, which is soldered to a channel 20, the leads into the housing of a vacuum pump 21.

As can best be seen in FIG. 2, the sublimation device 11 according to the invention consists of one end of a heat-resistant wire 22, and an overlap 23 · The wire 22 is preferably a long core, for example made of tungsten or tantalum. With a typical In the embodiment, the wire 22 has a tungsten core of 0.76 mm (30 mil.) Diameter and 15 cm (δ inch) length.

The layer 23 consists of several wires 24 made of getter material and a single wire 25 made of a heat-resistant metal, for example molybdenum or ilioebium, which is wound tightly around the wire 22 in a helical manner

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are, so that the · layer 23 is in direct thermally conductive> β * ::; ::. "<- ■ contact with the wire" 22 ■, namely over its entire length;. * :, ^: ; In Viner's preferred embodiment, 'the getter material' is titanium. «* /; Any of a variety of materials or alloys can ■ Jo ^; -: yes ^; serve as animal material "in the Süblimatiönereinriehtüng according to the Kr- 'Tinduhg. Zircon, uranium and other metals, in particular · in:" - ■' ■? - "· Groups IV and" V "of the periodic system of elements, can ' Aluminum, alkaline earth metals and alkali metals are other metals which can advantageously be used. In addition, the wires 24 preferably have a diameter on the order of the diameter of the wire ^; 22 ~ desolate ^; a slightly larger diameter. '' ■ · '■''■■' · '■ · ■ - -

The exact function of the heat resistant wire 25 is not fully k'lar. ^"J He 'but daäu at," deae the flow contributes "'" ⁰ ^ ^ prevent getter 'materials when söhmilzt. When a flow occurs / large drops form, which line with the wire ^! 'can and' cause a * burnout. The diameter "of the" ^l '*' ^: wire 25 should be · smaller "than the 'diameter of the wire' 22 'lind ^{! Iξ; Λ} preferably half as large.''''*""''*"'"

In a typical embodiment ^: the L'age 2J is composed of three wires, two titanium wires of 0.79 mm (31 mil.) Diameter and one molybdenum wire of 0.38 C ^ 5 mil.) Diameter.

During operation, the umpe 21 and the system to be evacuated (not shown), to which the pump 21 is connected, partially evacuated (pre-pumped) with a mechanical or a , 909818/0719 ^

-τ -

(not shown) to 10 microns. An unconnected power source of e.g. 5 - 6 volts will be used then connected to one of the sublimation devices 11 and electricity sent through this, for example 30 amps, which is not is sufficient to cause sublimation of the getter material, however causes outgassing of the same. The evolved gas is The fore-vacuum system is pumped out, and this can then be separated from the system “The voltage supply is then increased to 45 - 47 amperes in order to cause the getter material to sublime. at With significantly higher currents, getter 24 is overheated and melts, alloyed with the wire 22 and corrodes it, even if the device 11 can be operated briefly with higher currents without that it will be destroyed. * -

The diameter of the wire 22 can be selected within a wide range will. The relative dimensions of the getter material wires 22 and the heat-resistant single wire ·· 25 with regard to the cross-sectional dimension of the wire »22 are chosen so that a maximum utilization de · available getter material is achieved. Effective sublimation of the getter material occurs at and slightly below the point Point at which the cross section of the getter material is of the order of magnitude of the cross section of the wire 22. However, if the cross section of the getter material 24 is noticeably larger than that of the wire 22, it is difficult to wrap the wires around the core wire, * and it more current is required to achieve effective sublimation of the getter material, so that the higher current requirement can lead to the wire burning through. The dimensions of the single wire are chosen so that the highest possible getter material density per

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Unit of length is achieved and the single wire still does its job, to prevent a getter material flow, can effectively meet.

A single layer is preferable to a multi-layer coating, because, for example, multi-layer coatings are generally more difficult to manufacture in large quantities. In addition, the Single layer according to the invention with the currently available power sources compatible as far as current and voltage requirements are concerned.

For optimal utilization of the getter material, the getter should be proportional sublimated to pressure in the system. At high pressures, the getter is consumed quickly, and the sublimation device should therefore

- 5 be in operation halfway. At pressures below 10 Torr to

R.
down to about 10 "Torr, operation at about 25 ° / ° of the time is sufficient to remove gas as quickly as it enters the system. If the sublimation device is operated periodically, make sure that the initial current is not exceeded, Sublimation devices of the type described herein have been manufactured and have an approximate operating life of 20 hours in continuous operation. In addition, about 70% of the available getter material is consumed, which is about 40 % better than any known one Sublimation Device. When operated in conjunction with ion pumps, useful pumping speeds in the range of 0.1 to 10 " ¹² Torr and at even lower pressures have been achieved.

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Claims (2)

■ PATENT ADVOCATE
DI PL-MG .. .H. KLA US BE RN H AR DT 8000 MÖNCHEN 23 MAINZERSTR. 5 Y1 Ρ6θ D Pa t en tan s ρ r ü c h e: / 1 Λ sublimation device, consisting of a heat-resistant wire and a layer thereon that is directly thermally conductive Contact with the wire is characterized, that the Layer of at least two wires of getter material and a single wire consists of a heat-resistant metal. 2. Device according to claim 1, characterized in that the heat-resistant wire has a diameter d, the G-etter material wires have a diameter in the order of magnitude of d, and the single wire made of heat-resistant metal has a diameter smaller than d. 5 «device according to claim 2, characterized in that the single wire made of heat-resistant metal has a diameter of about d / 2. 4 · Device according to claim 1, 2 or 5 ,. characterized in that the permanent wire is a tungsten wire; is and that the layer consists of two titanium wires and one molybdenum wire.