EP2942800B1 - Fixed anode x-ray tube with two-part high voltage vacuum feed through - Google Patents

Description

• einen Isolationskörper aus keramischem Material, wobei der Isolationskörper einen durchgehenden Hohlraum aufweist,
• und eine Anode, wobei die Anode mit einem hinteren Ende im Hohlraum des Isolationskörpers angeordnet ist und den Hohlraum vakuumdicht verschließt.

Eine solche Vakuumdurchführung ist beispielsweise aus der DE 10 2009 017 924 A1 bekannt geworden.The invention relates to a high voltage vacuum feedthrough for an electron tube, in particular for a solid anode X-ray tube

• an insulating body of ceramic material, wherein the insulating body has a continuous cavity,
• and an anode, wherein the anode is arranged with a rear end in the cavity of the insulating body and closes the cavity vacuum-tight.

Such a vacuum feedthrough is for example from the DE 10 2009 017 924 A1 known.

X-ray radiation is used in a variety of ways in instrumental analysis or for the production of image recordings of human and animal patients in medicine. The generation of X-radiation is typically carried out in an X-ray tube by emission of electrons on an electrically heated electron emitter, and acceleration of the electrons in the electric field to a so-called target, is released at the characteristic X-rays; the target material differs depending on the application. The electron emitter is part of a cathode, and the target part of an anode.

In order to be able to accelerate the electrons sufficiently to the target, on the one hand, the space between the cathode and the anode must be evacuated. On the other hand, a high voltage (typically a few kilovolts) must be applied between the cathode and the anode. Mostly the anode is placed on high voltage, for which a corresponding vacuum-tight implementation is needed. A high-voltage vacuum feedthrough usually comprises a ceramic body as an electrical insulator with a central opening into which a high-voltage supply and an electrode are inserted in a vacuum-tight manner, cf. to the EP 1 537 594 B1 ,

In one embodiment of the DE 10 2009 017 924 A1 the anode is made of copper and is soldered vacuum-tight in a tubular ceramic insulation body made of aluminum nitride.

However, copper and ceramics such as aluminum nitride have quite different thermal expansion coefficients, so that when soldering or under load (and heating) in operation large mechanical Strains can occur, whereby the solder joint can be leaking; the x-ray tube is then unusable.

In the DE 10 2009 017 924 A1 It is proposed to form the anode on the outside with elastic claws. These can absorb the mechanical stresses elastically and also adjust the heat flow. Alternatively, it is proposed to drain the anode into a soft-annealed, hollow-cylindrical section, in which only slight mechanical stresses occur.

The production of elastic claws at the anode is very complex, and the vacuum-tight soldering with the ceramic insulation body is much more difficult than an anode with a smooth outer wall. An anode with a hollow cylindrical section is only suitable for relatively small heat fluxes, that is to say X-ray tubes with comparatively low power; adds that the hollow cylindrical section can be easily deformed during installation and therefore the vacuum-tight soldering is in turn difficult.

The relatively complex installation process of an anode in a ceramic insulation body also ensures comparatively long delivery times, if not for each Targettyp manufactured vacuum feedthroughs should be stored. After installing an anode in the insulating body, it is hardly possible in the prior art to change the target at the front end of the anode.

Object of the present invention

It is the object of the present invention to provide an easy-to-manufacture high-voltage vacuum feedthrough, which can be reliably formed vacuum-tight and reliably remains vacuum-tight during operation, in particular wherein the high-voltage vacuum feedthrough can also be easily equipped with different target materials.

Brief description of the invention

This object is achieved by a high-voltage vacuum feedthrough of the aforementioned doctor, as described in claim 1.

The present invention provides for the anode to be formed in two parts in order to be able to better fulfill the practical requirements for this component.

A rear portion of the anode is mainly used for attachment in the ceramic insulation body. The first metallic material of the rear portion is chosen so that its coefficient of thermal expansion α _ht corresponds to the coefficient of thermal expansion of the ceramic material of the losationskörpers α _ker , so that during soldering and also during operation of the electron tube (in which the anode heats up) no or so low mechanical Tensions occur that the tightness of the soldering between the rear portion and the insulating body is not affected.

In particular, the rear portion with a very narrow gap (about 50 microns gap width or less) can be soldered into the insulation body, which can be easily vacuum-tight bridged or closed with a solder. The rear portion is usually soldered vacuum-tight in the front half of the insulating body in the cavity.

The linear thermal expansion coefficients α _ht and α _ker correspond in particular when α _ht differs from α _ker by a maximum of 50%, preferably by a maximum of 25% (based on α _ker ); Preferably, α _{ht is} not greater than α _ker . Typically, α _{ht is} about 5-6 * 10 ^-6 1 / K, more preferably about 5.5 * 10 ^-6 1 / K in Fernico, and α _{ker is} about 6.5-8.9 * 10 ^-6 1 / K, in particular about 7 * 10 ^-6 1 / K with Al ₂ O ₃ ceramic.

The front part of the anode is mainly used to dissipate heat from the target, ie the area of the anode which is irradiated by electrons. The target is formed in the simplest case of a front end of the front portion, or the target is a coating or a (mostly soldered) essay or use at the front end of the front portion. The front portion consists wholly or partly (except for the target) of the second metallic material whose thermal conductivity λ _{vt is} greater than the thermal conductivity of the first metallic material λ _ht ; typically λ _vt ≥ 5 * λ _ht , and preferably λ _vt ≥ 10 * λ _ht . Due to the relatively high thermal conductivity of the second metallic material, the heat generated at the target can be efficiently dissipated.

Typically, λ _{vt is} about 300-400 W / (m * K), in particular about 380 W / (m * K) for copper, and λ _ht about 10-30 W / (m * K), in particular about 16.7 W / (m * K) at Fernico.

The rear section can be independent of the front section, and thus independent of the desired target material, in the insulation body be soldered. If it is established which target material is desired for the electron tube, then a corresponding front section can later be attached to the soldered rear section. For all types of target material, it is sufficient to maintain the same partially installed vacuum feedthrough (with insulation body and soldered rear section). For different target materials, various corresponding front sections (also called anode heads) can be stored.

The connection of the rear section and the front section can be done in any suitable manner which allows a sufficiently good heat transfer between the front section and the rear section and ensures an electrically good contact; However, preference is not welded or soldered to not affect the strength or tightness of the solder joint between the rear portion and insulation body subsequently. The connection generally provides for continuous, surface contact between the front section and the rear section. For connection in particular plugging / nesting and shrinking has proven. But it is also well, for example, by screwing / lneinanderschrauben, possibly with locking pin, well possible.

Preferred embodiments of the invention

In a preferred embodiment of the vacuum feedthrough according to the invention, the rear section and the front section are inserted into one another. Through a connector, a large contact area can be easily set up. The connector can also be fixed by shrinking, or with a locking pin.

An advantageous development of this embodiment provides that rear section front end a receiving portion with a recess in that the front section has a plug-in section at the rear end, and in that the plug-in section is inserted into the receiving section. In this case, the heat can pass over a very short distance from the plug portion of the front portion radially through the wall of the receiving portion of the rear portion in the insulating body. In addition, in the case of shrinking the easy-to-use and less sensitive front section to be frozen deep (such as in liquid nitrogen), and the insulation body together with the rear section to expand the receiving section gently heated (such as in an oven, eg at about 200 ° C).

It is preferred that the front portion has a longitudinal bore to the bottom of the recess of the receiving portion and a transverse bore which is connected to the longitudinal bore, and that the transverse bore opens out of the receiving portion. Due to the longitudinal bore and the transverse bore, gas (in particular air) can reliably escape to the outside of the recess of the receiving section when the front and rear sections are inserted one inside the other. Gas inclusions, which can cause poor heat transfer or mechanical stresses during operation, are avoided.

Most preferably, the rear portion and the front portion are connected by shrinking. This allows a very reliable, mechanically high-strength connection of front and rear section without solder or additional fastening or securing means. For this purpose, the male part (typically the front part) is strongly cooled, for instance in liquid nitrogen, and / or the female part (typically the rear part) is heated (for example to 200 ° C, but without softening the solder to the insulating body). Then, the two sections are inserted into each other, with little play, for example, 4/100 mm or less based on the diameter of the Receiving portion. Subsequently, when the plugged portion heats up, it expands and the receiving portion cools and shrinks; Finally, the two sections each block the heat-related geometry change of the other section. As a result, the two sections are elastically braced against each other and firmly connected. The inserted section is then under compressive stress, and the female section under tension.

In an advantageous embodiment, it is provided that the ceramic material of the insulating body is Al ₂ O ₃ , and the first metallic material of the rear portion consists of an iron-nickel-cobalt alloy, in particular with proportions by weight of Fe = 53-54%, Ni = 28-29%, Co = 17-18%. The stated weight fractions of the iron-nickel-cobalt alloy correspond to a so-called Fernico alloy. Al ₂ O ₃ ceramic and Fernico have very good matching coefficients of thermal expansion, with α (Al ₂ O ₃ ) of about 7 * 10 ^-6 1 / K, and α (Fernico) of about 5.5 * 10 ^-6 1 / K. This material combination has proven itself well in practice.

Also particularly preferred is an embodiment in which the second metallic material of which the front section is partially or completely composed is Cu. Copper has a very good thermal conductivity of about 380 W / (m * K), and can therefore very efficiently dissipate heat from the target. When fully manufactured from Cu, the front portion is used directly as a target.

Also preferred is an embodiment in which the front portion at the front of a coating, an attachment or an insert of molybdenum, tungsten, rhodium, silver, cobalt or chromium is applied or arranged. The coating, the attachment or the insert is used as a target in order to use characteristic X-ray emission lines of the associated material. Typically, an attachment to the front portion of the anode soldered; an insert is placed in a recess at the front of the front section, and usually by soldering or encapsulation (such as copper) attached. A coating can be applied by sputtering, for example. Since only the coating, the attachment or the insert consists of the particular target material, the properties of the second metallic material (usually copper) can still be used, such as a high thermal conductivity.

Also advantageous is an embodiment in which the rear portion has a rear end socket portion with a recess for receiving a high voltage connector. A connector for connecting the power line is easy to set up and has proven itself in practice.

According to the invention, the insulation body in a front region has a wall thickness WSv which is greater than a wall thickness WSm in a middle region, the back segment extending at least partially in the middle region, wherein WSm ≦ 2/3 * WSv, and wherein at least 2/3 of the length of the rear portion extends in the central region. The insulating body has a comparatively poor Wäremleitfähigkeit. By thinning in the central region, the heat dissipation from the anode can then be improved, in particular to a seated cooling device, especially since the heat conduction in the rear portion of the anode is usually relatively poor. The high voltage connection is then better protected. The larger wall thickness in the front part improves the electrical insulation, in particular by a long path along the surface of the insulating body from the anode to a (usually grounded) housing or outdoor area. Typically, the insulating body further has a rear portion, at which the wall thickness relative to the central region again is enlarged, so that the insulating body is constructed approximately dumbbell-shaped; this improves the grip of a seated cooling device.

According to the invention, a cooling device is seated on the outside of the insulating body in the central area. By the cooling device, the heat dissipation from the insulation body, in particular in the thinned middle area, can be improved. It is preferred in this case if the cooling device comprises a metallic casing of the insulating body, in particular wherein the metallic casing is made of copper or aluminum. The metallic sheath, with a higher thermal conductivity than the material of the insulating body, can carry heat away from the insulating body and spread over the length of the metallic sheath, thereby preventing local overheating in the region of the anode. The metallic sheath is typically in several parts, approximately in two parts, designed to facilitate attachment to the insulating body. The metallic sheath is typically significantly longer than the back section, approximately more than twice as long as the rear section. The metallic sheath may comprise cooling fins and / or be impinged by a cooling air flow. A coolant flow, such as air or water, through the cooling device is possible, but rarely required in practice.

Also preferred is an embodiment of the vacuum feedthrough according to the invention, in which the rear section is soldered into the insulation body with an Ag or Au-containing solder, wherein the insulation body has a nickel-plated MoMn coating at least in the soldered area. In this way, the metallic rear section can reliably solder vacuum-tight with the ceramic insulation body.

The scope of the present invention also includes an electron tube, in particular a solid-state x-ray tube, comprising a vacuum feedthrough according to the invention as described above. The electron tube is very reliable, and a failure due to a leak of the vacuum feedthrough, in particular by heating during operation, is not expected.

Process for producing a vacuum feedthrough according to the invention

1. a) Fertigung des Isolationskörpers,
2. b) Einsetzen des hinteren Teilstücks der Anode in den Hohlraum des Isolationskörpers und vakuumdichtes Einlöten des hinteren Teilstücks in den Isolationskörper;
3. c) Befestigen des vorderen Teilstücks der Anode am hinteren Teilstück. Durch das erfindungsgemäße Vorgehen kann sehr zuverlässig die Dichtigkeit der Vakuumdurchführung gewährleistet werden. Das Herstellungsverfahren ist zudem sehr flexibel bezüglich des Targetmaterials am vorderen Teilstück.

Also within the scope of the present invention is a method for producing a vacuum feedthrough according to the invention, described above, comprising the following steps:

1. a) production of the insulating body,
2. b) inserting the rear portion of the anode in the cavity of the insulating body and vacuum-tight soldering the rear portion in the insulating body;
3. c) attaching the front section of the anode to the rear section. By the procedure according to the invention, the tightness of the vacuum feedthrough can be ensured very reliably. The manufacturing process is also very flexible with respect to the target material on the front section.

A preferred variant of the method according to the invention provides that in step c) the fastening of the front section takes place at the rear section by plugging and shrinking. This makes it possible in a simple manner, a high-strength connection of the front and rear portion of the anode without solder or additional connecting means, in particular easily after step b).

Also advantageous is a variant in which steps a) and b) are initially carried out for a large number of vacuum feedthroughs, and later the partially manufactured vacuum feedthroughs individually or in groups according to Step c) are provided with front sections, wherein several different types of front sections are used. By doing so, a supply of semi-finished vacuum feedthroughs can be used for various target materials. The joining of the front and rear sections, such as over plugging and shrinking, is very quickly possible, so that an anode vacuum feed with a specific target material can be provided and delivered at short notice.

Further advantages of the invention will become apparent from the description and the drawings. Likewise, according to the invention, the above-mentioned features and those which are still further developed can each be used individually for themselves or for a plurality of combinations of any kind. The embodiments shown and described are not to be understood as exhaustive enumeration, but rather have exemplary character for the description of the invention.

Detailed description of the invention and drawing

Fig. 1

einen schematischen Längsschnitt durch einen keramischen Isolationskörper, in Hantelform, für eine Hochspannungs-Vakuumdurchführung gemäß der Erfindung;

Fig. 2

einen schematischen Längsschnitt durch eine teilgefertigte Hochspannungs-Vakuumdurchführung gemäß der Erfindung; mit einem Isolationskörper in Hantelform gemäß Fig. 1;

Fig. 3

einen schematischen Längsschnitt durch eine Hochspannungs-Vakuumdurchführung gemäß der Erfindung, mit einem Isolationskörper in Hantelform und einem hinteren Teilstück einer Anode gemäß Fig. 2;

Fig. 4

eine schematische Außenansicht der erfindungsgemäßen Hochspannungs-Vakuumdurchführung von Fig. 3, mit noch nicht aufsitzender Kühlvorrichtung;

Fig. 5

die Hochspannungs-Vakuumdurchführung von Fig. 4 im Längsschnitt, mit aufsitzender Kühlvorrichtung;

Fig. 6

eine schematische Außenansicht eines vorderen Teilstücks einer Anode für eine erfindungsgemäße Hochspannungs-Vakuumdurchführung, vollständig aus Kupfer gefertigt;

Fig. 7

eine schematische Außenansicht eines vorderen Teilstücks einer Anode für eine erfindungsgemäße Hochspannungs-Vakuumdurchführung, mit einem Einsatz aus Wolfram am vorderen Ende;

Fig. 8

einen schematischen Längsschnitt einer erfindungsgemäßen Hochspannungs-Vakuumdurchführung, mit einem keramischen Isolationskörper von im Wesentlichen einheitlicher Wandstärke;

Fig. 9

einen schematischen Längsschnitt einer erfindungsgemäßen Elektronenröhre, mit einer erfindungsgemäßen Hochspannungs-Vakuumdurchführung gemäß Fig. 5.

The invention is illustrated in the drawing and will be explained in more detail with reference to embodiments. Show it:

Fig. 1

a schematic longitudinal section through a ceramic insulation body, in dumbbell shape, for a high voltage vacuum feedthrough according to the invention;

Fig. 2

a schematic longitudinal section through a partially manufactured high voltage vacuum feedthrough according to the invention; with an insulating body in dumbbell shape according to Fig. 1 ;

Fig. 3

a schematic longitudinal section through a high voltage vacuum feedthrough according to the invention, with an insulating body in dumbbell shape and a rear portion of an anode according to Fig. 2 ;

Fig. 4

a schematic outside view of the high-voltage vacuum feedthrough according to the invention of Fig. 3 , with not yet mounted cooling device;

Fig. 5

the high voltage vacuum feedthrough of Fig. 4 in longitudinal section, with mounted cooling device;

Fig. 6

a schematic external view of a front portion of an anode for a high voltage vacuum feedthrough according to the invention, made entirely of copper;

Fig. 7

a schematic external view of a front portion of an anode for a high-voltage vacuum feedthrough according to the invention, with a tungsten insert at the front end;

Fig. 8

a schematic longitudinal section of a high-voltage vacuum feedthrough according to the invention, with a ceramic insulation body of substantially uniform wall thickness;

Fig. 9

a schematic longitudinal section of an electron tube according to the invention, with a high-voltage vacuum feedthrough according to the invention according to Fig. 5 ,

The FIGS. 1 to 3 illustrate the manufacture of a high-voltage vacuum feedthrough according to the invention in various staggered stages.

First, a ceramic insulating body 1 is manufactured or provided, cf. Fig. 1 , The insulating body 1 is here made of alumina ceramic, for example by slip casting or other known per se molding processes, and then sintering; The Al ₂ O ₃ ceramic may, if desired or required, contain sintering aids or other additives to optimize the manufacturing process or the quality of the sintered ceramic in a manner known per se.

The insulating body 1 has a substantially tubular construction, and has in particular a longitudinal cavity 10 extending in the longitudinal direction (see longitudinal axis LA), similar to a bore. The insulating body 1 is constructed here rotationally symmetrical with respect to the longitudinal axis LA. The cavity 10 has a step 11 which serves as a stop for a from the front (here right) End 12 ago to be introduced, rear portion of an anode is used (see. Fig. 2 ). From a rear (left here) end 13 fro a high voltage line to the anode can be performed (not shown).

The insulating body 1 also has in a front region VB over an (average) wall thickness WSv, which is greater than the (average) wall thickness WSm in a central region MB. In addition, in a rear region HB, the (average) wall thickness WSh is again greater than in the middle region MB. As a result, the insulating body receives a dumbbell-like appearance. Front area VB, middle area MB and rear area HB extend together over the entire axial length of the insulation body 1.

In the insulating body 1 and its cavity 10, a rear portion 2 of an anode is then introduced, see. Fig. 2 , and externally circumferentially soldered to the inner wall of the cavity 10. For this purpose, the insulating body 1, at least in an area adjacent to the right of the stage 11 inside initially provided with a MoMn coating, about CVD method, and be soldered with an Ag or Au-containing solder. The soldering is performed vacuum-tight, which is easily possible with sufficiently narrow gap between the rear portion 2 and the inner wall of the insulating body 1. The rear section 2 is here made of a Fernico alloy whose coefficient of thermal expansion corresponds to the thermal expansion coefficient of the insulating body 1 (both with respect to the radial direction, as well as the axial longitudinal direction).

By the rear portion 2 and the soldering of the cavity 10 is sealed vacuum near the front end 12, ie a gas exchange between the front end 12 and the rear end 13 through the cavity 10 is no longer possible.

The rear portion 2 has the rear end via a socket portion 14 with a recess 15 for receiving a high voltage plug (the latter not shown in detail). At the front end, the rear portion 2 has a receiving portion 16 with a recess 17 for receiving a plug-in portion of a front portion of the anode (see Fig. 3 ).

The insulating body 1 with soldered rear section 2 of the anode, but without installed front section, is also referred to as a partially manufactured vacuum feedthrough 34.

Then, the attachment of a front portion 3 of the anode, see. the Fig. 3 to complete the vacuum feedthrough 23. This front section 3 has at the rear a plug-in section 18 which is inserted into the recess 17 of the rear section 2.

For this purpose, the front portion 3 is first strongly cooled here, typically to the temperature of liquid nitrogen (about 90 K), in which the front portion 3 is immersed, so that the plug portion 18 contracts radially. In addition, the rear portion 2 is heated together with the insulating body 1, such as in an oven at 200 ° C, so that the recess 17 radially expands. At these temperature conditions, the plug-in section 18 can just be introduced into the recess 17. Once the temperature conditions normalize, so the front and the rear section 3, 2 are at the same temperature, the recess 17 has radially contracted so far and the plug portion 18 radially expanded so far that the front and rear section 3, 2 radially are clamped together and can not be deducted from each other.

To air inclusions between the recess 17 and the plug insert 18, in particular at the bottom 33 of the recess 17, when mating avoid, in the front part 3, a longitudinal bore 19 and a hitting the longitudinal bore 19 transverse bore 20 are provided. Air can then escape from the base 33 of the recess 17 through the holes 19, 20, if the gap between the side wall 21 of the receiving portion 16 and the outer wall of the plug portion 18 is too narrow for a gas outlet.

Here, the front section 3 is made entirely of copper, in order to ensure rapid and efficient heat transport from the region of the target 22 at the front end of the front section 3 of the anode into the insulation body 1 during operation. The heat flow takes place mainly by the front portion 3 to the plug portion 18, through the side wall 21 of the receiving portion 17 of the rear portion 2 and partially by the other rear portion 2, in the insulation body 1 instead.

If desired, a coating, an attachment or an insert of material other than copper may be provided at the front end of the front section 3 in order to generate X-radiation characteristic of the target 22 in accordance with this other material (cf. Fig. 7 ).

The front section 3 protrudes from the front of the insulation body 1. The vacuum feedthrough 23 is intended to be integrated into an electron tube or X-ray tube (cf. Fig. 9 ).

How out Fig. 4 it can be seen, the vacuum feedthrough 23 may be provided with a cooling device 4, which here consists of a metallic sheath, preferably made of copper or aluminum. In the embodiment shown, the casing comprises two half-shells 4a, 4b, which are placed around the insulating body 1 and enclose it over a large area over virtually the entire circumference and the entire length of the central region MB. In order to compensate for temperature-induced changes in length with sufficiently low mechanical stresses, have the Half shells 4a, 4b here each rear end a multi-slotted area 4c on.

Fig. 5 shows the vacuum duct 23 with installed half-shells 4a, 4b, applied to the insulating body 1, in longitudinal section. The half-shells 4a, 4b are to be reached via short paths, namely by the reduced wall thickness WSm of the insulating body 1 in the middle region MB (compared to the larger wall thickness WSv in the front region VB) from the rear section 2 of the anode for the heat flow emanating from the target 22 ,

The rear section 2 extends here in the longitudinal direction to about 9/10 in the central region MB, and the (average) wall thickness WSm in the central region MB is here about 1/2 times the (average) wall thickness WSv in the front region VB. The heat can be distributed and emitted / radiated in the half shells 4a, 4b of the cooling device 4 over its entire length, thereby avoiding local overheating of the anode, in particular the rear section 2, which is connected to a high-voltage connector.

In general, it is preferred if the rear section 2 extends axially at least 2/3 in a region of the insulation body 1 in which the local radial wall thickness (see WSm in the middle region MB) of the insulation body 1 is at most 2/3 of the largest Radial wall thickness (see WSv in the front region VB) of the insulating body 1 is.

Fig. 6 shows a front portion 3 of an anode for the invention. The section 3 is here completely made of copper. At the rear end, the section is provided with a plug-in section 18, and the target 22 is formed through the front end. The planar surface of the target 22 is slightly oblique to the longitudinal axis LA to provide a useful radiation characteristic (Angular distribution) of the incident by electrons in the copper triggered characteristic X-ray radiation.

If the characteristic X-ray radiation of a material other than copper is desired, the front section 3 can be provided at the front end with an insert 24 (shown in phantom) of the other material ("target material"), here tungsten, as the target 22, cf. Fig. 7 , The insert 24 is arranged on the front portion 3 in a local recess 24 a and fixed (soldered about), usually before the front portion 3 is attached to the rear portion 2. The flat surface of the insert 24 is also inclined with respect to the longitudinal axis LA.

The Fig. 8 shows an alternative embodiment of a high voltage vacuum feedthrough 23 according to the invention, in which the ceramic insulating body 1 is formed with substantially uniform wall thickness WS. This design is particularly simple, and can be used well with electron tubes or X-ray tubes with low power or low heat generation at the target 22.

In the Fig. 9 is a schematic longitudinal section of an electron tube 25 (here a solid anode X-ray tube) with a vacuum feedthrough 23 according to the invention as shown Fig. 5 known.

Around the front portion 3 of the anode 28 and adjacent to the insulating body 1, a vacuum-tight housing 30 is arranged, in which an evacuated space 31 is arranged. In the housing 30, a cathode 27 is further arranged with an electron emitter 26, here an electrically heated coil of tungsten wire.

From the electron emitter 26 occur in operation by annealing emission electrons, which by a high voltage between the cathode 27 and Anode 28 of typically 5 kV to 30 kV through the evacuated space 31 to the anode 28, more precisely to the target 22 at the front portion 3, are accelerated. There is then - in addition to the bremsstrahlung - characteristic X-rays 29 triggered, which emerge through a Berylliumfenster 32 and can be used, such as for instrumental analysis or medical diagnostics.

Even if the soldering between the metallic rear portion 2 of the anode 28 and the ceramic insulating body 1 should become hot during operation, no strain-induced mechanical stresses occur at the soldering because the thermal expansion coefficients α _ht and α _{ker of} the rear portion 2 from Fernico and the ceramic material Al ₂ O _{3 of} the insulating body 1 are approximately equal. At the same time, heat from the target 22 is efficiently returned well through the copper material of the front section 2 (in FIG Fig. 9 to the left).

Claims (14)

1. A solid anode X-ray tube (25) having a high voltage vacuum feed through (23) comprising:

   - an insulating body (1) made of ceramic material, the insulating body (1) having a continuous hollow space (10),

   - and an anode (28), wherein a rear end of the anode (28) is arranged in the hollow space (10) of the insulating body (1) and seals the hollow space (10) in a vacuum-tight fashion,

   wherein the anode (28) has a two-part design with a rear part (2) and a front part (3),
   the rear part (2) being made from a first metallic material having a thermal expansion coefficient α_ht which corresponds to the thermal expansion coefficient α_ker of the ceramic material,
   wherein the rear part (2) is arranged in the hollow space (10) of the insulating body (1) and is soldered into the insulating body (1) in a vacuum-tight fashion,
   the front part (3) consisting at least partially of a second metallic material having a heat conductivity λ_vt which is larger than the heat conductivity X_ht of the first metallic material of the rear part (2),
   and wherein the front part (3) is mounted to the rear part (2), characterized in
   that the insulating body (1) has a wall thickness WSv in a front area (VB) which is larger than a wall thickness WSm in a central area (MB), wherein the rear part (2) extends at least partially in the central area (MB),
   that WSm≤2/3*WSv, that at least 2/3 of the length of the rear part (2) extends in the central area (MB),
   and that a cooling device (4) is seated on an outside of the insulating body (1) in the central area (MB).
2. The solid anode X-ray tube (25) according to claim 1, characterized in that the rear part (2) and the front part (3) are inserted into each other.
3. The solid anode X-ray tube (25) according to claim 2, characterized in that the rear part (2) comprises, at a front end thereof, a receiving section (16) having a recess (17),
   that the front part (3) has a plug-in section at a rear end thereof, and that the plug-in section (18) is inserted into the receiving section (16).
4. The solid anode X-ray tube (25) according to claim 3, characterized in that the front part (3) has a longitudinal bore (19) extending to a bottom (33) of the recess (17) of the receiving section (16), the front part (3) also having a transverse bore (20) which is connected to the longitudinal bore (19), and that the transverse bore (20) terminates outside of the receiving section (16).
5. The solid anode X-ray tube (25) according to any one of the claims 2 to 4, characterized in that the rear part (2) and the front part (3) are connected to each other through shrinking.
6. The solid anode X-ray tube (25) according to any one of the preceding claims, characterized in that the ceramic material of the insulating body (1) is Al₂O₃ and the first metallic material of the rear part (2) is made of an iron nickel cobalt alloy, in particular with weight portions of Fe=53-54%, Ni=28-29% and Co=17-18%.
7. The solid anode X-ray tube (25) according to any one of the preceding claims, characterized in that the second metallic material, of which the front part (3) partially or completely consists, is Cu.
8. The solid anode X-ray tube (25) according to any one of the preceding claims, characterized in that a front end of the front part (3) has a coating, a top part or an insert (24) of molybdenum, tungsten, rhodium, silver, cobalt or chromium.
9. The solid anode X-ray tube (25) according to any one of the preceding claims, characterized in that a rear end of the rear part (2) comprises a connector section (14) having a recess (15) for receiving a high voltage plug.
10. The solid anode X-ray tube (25) according to any one of the preceding claims, characterized in that the cooling device (4) comprises a metallic sheathing of the insulating body (1).
11. The solid anode X-ray tube (25) according to any one of the preceding claims, characterized in that the rear part (2) is soldered into the insulating body (1) with a solder containing Ag or Au, the insulating body (1) having a nickel-plated MoMn coating, at least in the soldered area thereof.
12. A method for producing a vacuum feed through (23) of a solid anode X-ray tube (25) according to any one of the preceding claims 1 to 11, the method comprising the steps of:

    a) producing the insulating body (1);

    b) inserting the rear part (2) of the anode (28) into the hollow space (10) of the insulating body (1) and vacuum-tight soldering of the rear part (2) into the insulating body (1);

    c) mounting the front part (3) of the anode (28) to the rear part (2).
13. The method according to claim 12, characterized in that the front part (3) is mounted to the rear part (2) in step c) through plugging on and shrinking.
14. The method according to claim 12 or 13, characterized in that steps a) and b) are initially performed for a plurality of vacuum feed throughs (23), and the partly finished vacuum feed throughs (34) are subsequently provided with front parts (3), either individually or in groups in accordance with step c), wherein various different types of front parts (3) are used.

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