ELECTRODE FOR A GAS DISCHARGE LAMP AND GAS DISCHARGE LAMP

Description

[0001] The invention is directed to discharge lamps and the electrodes arranged therein. In particular, the invention is directed to lamps with electrodes subject to high thermal stress, as is the case with short-arc discharge lamps, for example. Examples include mercury discharge lamps (e.g. OSRAM HBO ®< ) and xenon discharge lamps (e.g. OSRAM XBO ®< ), which can be used, among other things, for photolithographic applications (microchips, ICs, PCBs, LCD displays, etc.) or for projection applications (e.g. cinema projection). In principle, the invention can be used in all lamp-like light sources in which at least one electrode is arranged in a light-transmitting vessel (e.g. a glass bulb). In this respect, the invention can also be used in laser-based plasma light sources (so-called laser-sustained plasma light sources).

[0002] The electrodes, especially the anodes in the case of DC lamps, are exposed to significant thermal stress during lamp operation. Therefore, materials with very high temperature resistance are generally used, in the vast majority of cases, tungsten. Nevertheless, the temperatures generated by the action of the plasma or plasma arc on the front part of the anode lead to the evaporation of anode material. This can lead to degradation of the electrode and, on the other hand, to the deposition of the evaporated material in the interior of the discharge vessel, which can result in a decrease in light output and / or a reduction in lamp life.

[0003] The aim of the invention is therefore to ensure the best possible heat dissipation (heat dissipation) of the front electrode area close to the discharge arc, with particular emphasis on improving the thermal conductivity of the electrode.

[0004] There are several approaches designed to improve electrode cooling, i.e., heat removal from the electrode. One possibility is to coat the anode with materials that have better emissivity in the infrared range (e.g., Osram, DE 102009021235 B4). Microstructuring of the electrode surface (Ushio, JP3838110B2) is also used to improve heat radiation. Both of these methods serve to radiate heat from the surface of the electrode. Another approach aims to improve thermal conductivity along the electrode axis. For this purpose, the electrode can have an inner section or core region that has a higher conductivity than pure tungsten. One example is anodes that have a hermetically sealed interior filled with a low-melting metal, such as silver or copper (Ushio, EP 1357579 B1), or an alloy.Such anodes have been used in mercury discharge lamps for some time. At the temperatures prevailing during operation, the low-melting metal enclosed in the interior melts and can partially even transform into a gaseous state. During these melting or evaporation processes, thermal energy is absorbed by the low-melting metal and transported, among other things, via convection processes, from the front area of ​​the electrode facing the discharge arc to the rear area of ​​the electrode facing the electrode rod.

[0005] Details on the construction of a discharge lamp are shown in Fig. 18which schematically represents a gas discharge lamp 10 with the electrodes 1 and 2. The gas discharge lamp 10, which is preferably designed as a high-pressure mercury gas discharge lamp, represents a vertically operated discharge lamp 10, so that the electrode axes of the two electrodes 1 and 2, which run parallel to one another, in particular on a line, are also aligned vertically. Furthermore, the electrode 1 in this example is designed as a cathode with a cathode tip 11 and a cylindrical region 12, while the electrode 2 represents the anode and has an anode plateau 14 and also a cylindrical region 13. The anode 2 is arranged above the cathode 1 and the anode plateau 14 faces the cathode tip 11, wherein a discharge arc forms between the anode plateau 14 and the cathode tip 11 during operation.In addition, the two electrodes 1 and 2 are arranged in a discharge vessel 7, for example, a glass bulb. A cathode support rod 3 and an anode support rod 4 are provided to hold the electrodes in the discharge vessel 7. These are electrically connected to the connection bases 8 and 9 via internal power leads 5 and 6, respectively. The connection bases 8, 9 can in turn be connected to a power source via suitable external power leads (not shown) to operate the discharge lamp 10.

[0006] The high-pressure gas discharge lamp 10 is preferably operated at high power, particularly in the kilowatt range. This results in very high temperatures, especially at the anode 2. Typically, the temperature in the area of ​​the anode plateau is approximately 2700°C and, depending heavily on the anode's thermal conductivity and heat radiation capacity, drops to approximately 1500°C to 1100°C toward the anode support rod. In any case, the heat from the anode 2 must be dissipated as efficiently as possible to increase the service life of the anode 12 and to enable the required current-carrying capacity.

[0007] JP 2013 118202 A discloses an electrode for a gas discharge lamp which, for improved heat dissipation, has a number of open bores on the side of the electrode facing away from the discharge arc in order to increase the heat-emitting surface of the electrode and thus improve the overall heat dissipation of the electrode. DE 10 2011 106253 A1 discloses an electrode for a gas discharge lamp which has a chamber divided into further regions by a body such that vertical convection of the coolant, which is in the form of liquid metal, is possible, but convection in the circumferential direction is prevented. The object of the present invention is therefore to provide an electrode for a gas discharge lamp with improved properties. One aspect is to achieve the best possible heat dissipation of the electrode, in particular of the front electrode region close to the discharge arc.In particular, the thermal conductivity of the electrode should be improved.

[0008] This object is achieved by an electrode for a gas discharge lamp having the features according to claim 1. Advantageous embodiments of the invention are the subject of the dependent patent claims, the description and the figures.

[0009] As already mentioned at the beginning, the invention also relates to a gas discharge lamp with at least one electrode according to the invention.

[0010] The invention described below aims at increasing the thermal conductivity inside the anode, whereby the disadvantages of the single-chamber design described above in the prior art are to be overcome or at least reduced by means of a multi-chamber design. For this purpose, the anode / electrode has two or more chambers inside its usually cylindrical base body. In particular, the multi-chamber design is to be such that a more directed convection is achieved for more efficient heat transport. Furthermore, local heating is to be avoided and greater flexibility with regard to the lamp burning position is to be achieved. In addition, the multi-chamber design enables greater stability in the critical region of the electrode near the plateau. In total, the anode is to have n chambers with 2 ≤ n. The following designations apply (see also Fig.1C and corresponding character description): n - Number of chambersr i - shortest distance of chamber i to the edge of the anode si - shortest distance of chamber i to the plateau plane of the anode the - Diameter or largest dimension of the chamber parallel to the plateau a ij - minimum distance between chambers i and j

[0011] In one embodiment, the anode comprises a first anode part, the closure part or lid, and a second anode part, the vessel part or pot (recess in the base body of the electrode), both of which are hermetically connected to each other. The chambers are located in the lower part of the anode (pot). Some arrangement examples for the two or more chambers are shown in the Figures 3 to 9 (top view), whereby in these examples the chambers are arranged next to one another, i.e. the chambers or at least some of the chambers are arranged parallel to one another in a longitudinal direction of the base body.

[0012] The multi-chamber design according to the invention has the advantage of a very high degree of design flexibility, so that depending on the specific application - for example due to the lamp type (lamp filling, filling pressure, electrode diameter, electrode geometry, etc.), the lamp power, the lamp burning position and many other influencing factors - individual aspects of the above-described aspects can be given particular emphasis and preferably optimized.

[0013] In principle, all parameters of a particular chamber can be adjusted individually and, in principle, independently of other chambers. In addition to purely geometric parameters, such as those listed above, the surface properties of the chamber's interior walls can also be adjusted. Furthermore, it is possible to adjust the filling of each chamber individually, for example, with regard to the low-melting metal to be filled (material selection) or its fill level. Further optimization options exist in the arrangement of the individual chambers relative to one another and in relation to the outer wall of the electrode.

[0014] With regard to geometric dimensions, the chambers can, for example, all have the same shape and depth, which is particularly easy to implement in terms of manufacturing. Depending on the application, the chambers can also have different shapes and / or depths (see, for example, Fig. 7 , Fig. 12). Possible shapes can be differentiated, for example, by their cross-sectional area, with round (e.g. circular or oval) and angular (e.g. triangular, square or polygonal) shapes being possible. In principle, however, mixed shapes are also conceivable, in which a first cross-sectional area is present in a first section and a second cross-sectional area different from the first in a second section. In other words, a transition can take place across the longitudinal extent of the chamber, for example, from a round cross-section to an angular cross-section or from a circular cross-section to an oval cross-section.

[0015] Suitable manufacturing processes, especially for round chambers, include drilling, turning, or milling. Other chamber shapes (square, semicircular, etc.) can be produced, for example, as so-called feedstock anodes. In this case, a powder made of the carrier material (e.g., tungsten) and a binder is molded into almost any shape using a casting mold, for example. The binder is then extracted, and the blank is further densified.

[0016] In terms of the manufacturing process, a distinction must be made between those processes in which the individual chambers are formed from the base body of the electrode by machining (and in which a vessel or pot or a pot-like recess is created in the base body) and those processes in which the individual chambers are manufactured outside the base body of the electrode and inserted into the base body of the electrode in a subsequent process step, whereby the base body must have a suitably dimensioned cavity for this purpose.

[0017] As mentioned above, the multi-chamber design offers a high degree of flexibility, as essentially all geometric and non-geometric properties of the chamber can be individually adjusted, thus optimizing the overall system. In the following, exemplary embodiments of some of these geometric and non-geometric chamber properties will be explained in detail. Length of the chambers:

[0018] The length of the individual chambers can be adjusted, among other things, to achieve an optimal compromise between the best possible heat dissipation and electrode stability, depending on the respective position of the chamber in the (usually cylindrical) electrode body. For example, chambers located close to the symmetry axis of the electrode body can be shorter than chambers that are further away from the symmetry axis of the electrode body (see Fig. 12). Since particularly high temperatures occur near the plateau, in particular at the arc attachment point close to the symmetry axis of the electrode base body, with such an embodiment the distance si of the individual chambers i can be optimized depending on their position in relation to the arc attachment point in order to prevent the risk of deformation or even leakage in this area. Arrangement of the chambers:

[0019] The arrangement of the individual chambers i inside the electrode is preferably symmetrical, in particular rotationally symmetrical to the electrode's longitudinal axis. This has the advantage that the heat flow can be distributed evenly across the electrode cross-section (e.g., in a plane perpendicular to the electrode's longitudinal axis) in the case of a vertical burning position, which is frequently encountered in practice, in order to achieve efficient cooling of the electrode and to avoid local heating and damage. Possible arrangements are described in the Figures 3 to 6 , 8 and 9 shown.

[0020] In the case of a non-vertical burning position, a non-symmetrical, in particular non-rotationally symmetrical, arrangement of the chambers can help to adjust the convection currents and heat flows with respect to the direction of gravity. In one embodiment, for example, a larger number of chambers can be provided on the side of the electrode that is closest to the ground in the case of a lamp tilted away from the vertical than on the opposite side of the electrode (see Fig. 7 , where the electrode side shown to the right of the dashed line in the figure is the side closest to the ground).

[0021] In addition to adjusting the arrangement of the individual chambers, in the case of a non-vertical firing position, other geometric and non-geometric properties can also be adjusted, e.g. chamber geometry (diameter, length, shape), chamber filling (material, filling height) and the like. Filling the chambers:

[0022] In principle, each chamber can be filled independently of the others. This applies both to the type of materials filled and their quantity (vol% or mass%).

[0023] Suitable materials for the heat transfer described above are, in particular, low-melting metals, such as silver, copper, gold, and other metals known in the art with a lower melting point compared to tungsten and a higher thermal conductivity compared to tungsten. These materials are typically filled into the chambers as solids. In addition to the low-melting metal or alloys of low-melting metals, a protective gas, for example, a noble gas such as argon, can be enclosed in the respective chamber.

[0024] In addition, additional materials can be included in the respective chambers, which further increase the thermal conductivity without melting under operating conditions. These additional heat conductors can be non-metallic materials such as diamond or ceramic materials such as boron nitride, aluminum nitride, etc. These additional heat conductors are preferably introduced into the respective chamber in powder form. Details are disclosed in DE10 2018 220 944.8. Wall texture:

[0025] The nature of the interior surface of the individual chambers represents a further influencing factor with regard to their thermal behavior. Smooth chamber interior walls with surface roughness, which arises during the manufacturing processes described above (e.g., machining processes such as drilling, turning, or milling), are particularly easy to manufacture. Roughening or structuring of the surface can be achieved with the help of alternative or additional manufacturing processes, for example, through mechanical processes (e.g., sandblasting, sputtering, grinding, etc.), chemical processes (e.g., etching), or other physical processes (e.g., laser structuring, plasma etching, ion irradiation, etc.).The aim of such surface treatments can be to structure the surface in such a way that a heat exchanger with improved return transport of the working medium (here the low-melting metal) from the heat dissipation zone (anode support rod) to the heat source (anode plateau) can take place in the manner of a heat pipe (thermosiphon, heat pipe). The return transport takes place purely passively and can be accomplished by gravity and / or by other forces, such as capillary forces. Mesh structures, sintered structures, wick structures, grooves or channels, or combinations thereof, arranged on the inner surfaces of the chambers i, can be suitable for this purpose. Corresponding concepts are disclosed, for example, in DE 102007038909 A1. Number of chambers:

[0026] The optimal number of chambers depends on various factors, including the geometric properties of the individual chambers i (e.g. diameter, length, shape, etc.), the filling of the individual chambers i (material type, fill level, additional fill components, etc.), the wall properties of the chambers i, and the arrangement of the individual chambers i relative to one another. The individual factors can influence one another. For example, the achievable packing density of chambers i in the base body of the electrode depends on the diameter and shape of the individual chambers i. In addition, the ratio of the inner chamber surface to the chamber volume can play a role in achieving efficient, directed heat flow. Furthermore, the ratio of the chamber volume to the surrounding tungsten volume can play a role with regard to the current carrying capacity of the anode.As already mentioned, all these considerations may also depend on the operating conditions of the lamp, in particular its burning position. Cross-sectional area of ​​the chambers:

[0027] The conventional solution with only one chamber carries the risk of plateau deformation. With the present invention, the tendency to deformation can be reduced by selecting chambers such that the projection of the cross-sectional areas of the chambers onto the plateau only fills a part of the plateau (see, for example, Fig. 15). The area of ​​the plateau is A p with A p =π*p 2< / 4, where p is the diameter of the plateau. The projection of the chamber cross sections onto the plateau has the areas A 1 , A 2 , A 3 ...A n , The sum AS of the projected cross-sectional areas is therefore AS = A 1 +A 2 ...A n . For an advantageous design of the chambers, 0.1 < AS / A p < 0.9 should apply, particularly advantageous 0.3 < AS / A p < 0.8. At smaller values, the heat can no longer be dissipated efficiently through the material in the chambers. If the ratio is greater than 0.9, the risk of deformation of the plateau increases and the disadvantages of the conventional solution become apparent again. Distance between the chambers:

[0028] The distance a ij between the chambers can be chosen to be small, with a lower limit determined primarily by the machining process or the risk of crack formation during operation. Therefore, a ij ≥1 mm should apply. Distance of the chambers to the plateau and the edge:

[0029] The distance si between the chambers and the anode plateau is influenced by two things: firstly, the distance should be small to dissipate heat as effectively as possible. Secondly, it should be large to avoid deformations or cracks in the plateau. The tendency towards deformation increases with the diameter (or greatest extent) di of the chamber, i.e. by choosing a smaller diameter, the distance to the plateau can also be reduced. The distance si should ideally be at least 3 mm or at least di / 3, i.e. si ≥ di / 3 and si ≥ 2 mm. The distance ri between the chambers and the edge should - like the distance to the plateau - be small, because heat radiation via the anode jacket also effectively contributes to reducing the temperature at the plateau. The tendency towards deformation is lower due to the lower temperatures compared to the plateau and the lack of pressure from the plasma.However, cracks caused by stress must be avoided, so that the following relationship should advantageously be maintained: si ≥ di / 4 and si ≥ 2mm.

[0030] Alternatively or in addition to the embodiments described above, different chambers can also be arranged one behind the other along a longitudinal direction of the electrode, i.e. the chambers or at least some of the chambers can be arranged in series with one another in a longitudinal direction of the base body. Fig. 17BAn example is shown in which an anode has four chambers K1 to K4, which are arranged along a longitudinal direction A of the anode and thus form a stacked arrangement. In this example, the chambers each have the same dimensions (length, width, depth) and have a rectangular cross-section. As already described in detail above, there is a wide range of possible variations for these embodiments with regard to the geometric and non-geometric properties of the chambers, for example, their shape, their mutual spacing, their distances from the edges of the anode (side walls, lid, anode plateau), their fillings, their wall properties, etc.In particular, the individual chambers i can have different geometric and non-geometric features from each other, so for example, chambers near the anode plateau can have different geometric dimensions than those further away from the anode plateau.

[0031] In summary, the overall design of a multi-chamber electrode is a function of a multitude of parameters, some of which have been listed and explained above (not exhaustively), whereby the individual parameters can partly be selected independently of each other, but partly are also directly linked to each other. Sealing:

[0032] There are several methods available for sealing the chambers. a) One possibility is to close each individual chamber with a plug made of the same material as the lid (ie, closure part) and the pot / vessel part (ie, recess in the base body of the electrode), preferably tungsten. A plug is required for each filled chamber (see, for example, Fig. 13). This is designed, for example, with a groove all the way around. The part above the groove is wider to prevent slipping into the chamber opening. This groove now houses a coil made of a material that acts as a solder. By heating the solder, e.g., in a furnace, the individual chambers are sealed. The solder material must be selected so that it does not reliquefy during later operation. Suitable examples for anodes in mercury discharge lamps would be molybdenum / ruthenium, titanium / tungsten, zirconium / tungsten, or platinum / tungsten. The temperatures must be adapted to the respective application. b) In a variant of a), the solder is not introduced in the form of a coil, but as a metal foil that is wrapped around the plug and pressed into the chamber with it. The plug shape can be cylindrical or conical. The seal is created as under a) by a thermal step (e.g.,Furnace annealing). c) A third possibility is the application of solder to the end face of the pot, so that all chambers are separated from one another after the soldering process, but are essentially closed with one and the same plug (here, the end face of the pot). Examples are conceivable in which the solder is introduced into depressions in a spherical shape, see, for example, . Fig. 14 The dashed lines indicate recesses into which the solder is poured in the form of small beads. d) Another possibility is to provide the plug and the respective chamber with a screw thread so that the plug can be screwed into the chamber. Additionally, the plug can be sealed with solder.

[0033] The conventional single-chamber design has the disadvantage that the plateau can deform due to the strong thermal load. Under such loads, the resulting depression in the plateau area can become so large that the material can no longer withstand mechanical stress, and filler material (e.g., copper or silver) leaks from the anode, leading to lamp failure. Therefore, it is important to ensure that the distance s between the hole and the plateau is sufficiently large. On the other hand, the distance should be small to achieve the best possible heat dissipation.

[0034] The multi-chamber system allows the distance si the chambers to the plateau can be chosen smaller without causing such deformations and possible failure of the lamp.

[0035] Further advantages, features, and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. For the sake of simplicity, identical or similar features may be designated by the same reference numerals.

[0036] Showing: Fig. 1A is a schematic representation of a plan view of an anode according to an embodiment of the invention; Fig. 1B is a schematic representation of a sectional view of the anode from Fig. 1A ; Fig. 1C a schematic representation of a partial sectional view of the anode from Fig. 1A ; Fig. 2A is a schematic representation of a plan view of an anode according to a second embodiment of the invention; Fig. 2B is a schematic representation of a longitudinal section of the anode from Fig. 2A ; Fig. 2C a schematic representation of a cross-sectional view of the anode from Fig. 2A; Fig. 3-9 each show a schematic representation of a cross-sectional view of an anode according to seven further embodiments of the invention; Fig. 10 shows a schematic representation of a partial sectional view of an anode with an anode trough according to an embodiment of the invention; Fig. 11 shows a schematic representation of a partial sectional view of an anode with anode trough according to a further embodiment of the invention; Fig. 12 shows a schematic representation of a sectional view of an anode with chambers of different lengths according to an embodiment of the invention; Fig. 13 shows a schematic representation of a sectional view of an anode with a separate plug in a chamber and an additional cover; Fig. 14 shows a schematic representation of a plan view of an end face of an anode with three chambers according to an embodiment of the invention;15, 16 each show a schematic representation of the projection areas of the cross sections of three chambers onto the respective anode plateau; Figs. 17A, 17B each show a schematic representation of a top view and a longitudinal sectional view of an anode according to a further exemplary embodiment of the invention; Fig. 18 shows a schematic representation of a top view of a gas discharge lamp according to an exemplary embodiment of the invention.

[0037] The Figures 1A and 1Beach show a schematic representation of a top view and a sectional view along the longitudinal axis A of an anode 2 according to a first exemplary embodiment of the invention. The anode 2 consists of a circular-cylindrical vessel part 22, the pot, and a closure part 24, the lid. The pot 22 has an anode plateau 14 and several chambers, here two chambers 221, 222, which are formed as recesses in the base body of the pot 22. The two tubular chambers 221 and 222 are partially filled with silver 26 (symbolized as a dotted area). The end of the pot 22 opposite the anode plateau 14 is closed with the lid 24. At the same time, the cover 24 also closes the open ends of the two chambers 221, 222 opposite the anode plateau 14. The cover 24 has a bore 241 for the anode holder (not shown here).

[0038] In Figure 1CThe designations of some geometric dimensions introduced at the beginning are explained using a schematic representation of a partial sectional view of the anode 2 from Fig. 1A shown. Accordingly, L is the length of the anode 2 from the anode plateau 14 to the opposite connection-side end of the cover 24, D is the diameter of the anode 2, di is the diameter or greatest extent of the i-th chamber parallel to the anode plateau 14 (i = 1 to n; in the exemplary embodiment, n = 2), ri is the shortest distance of chamber i to the edge of the anode 2, si is the shortest distance of chamber i to the plateau plane 14 of the anode 2, a ij is the minimum distance between the chambers i and j (in the exemplary embodiment, this is the minimum distance a 12 between the two chambers 221 and 222).

[0039] The Figure 2A shows a top view and the Figures 2B and 2Cshow schematically a longitudinal and cross-sectional view of an anode 20 according to a second embodiment of the invention. Here, the pot 22 of the anode 20 has five chambers 221-225, each of which has a circular cross-section and is separately closed with an associated plug 261-265 (only two plugs 261 and 262 are shown in Fig. 2B shown).

[0040] The Figures 3 to 9 show a schematic representation of a cross-section of an anode (similar to Fig. 2c ) according to seven further embodiments of the invention. They differ in the number and / or shape and / or diameter of the chambers. To make the chambers easier to recognize, the cross section is taken through the silver-filled part, with the silver as in Fig. 1B symbolized as a dotted area. Fig. 3 shows an anode pot 22 with five chambers 221 - 225, similar to that already shown in Fig. 2C shown. Fig. 4shows an anode pot 22 with six chambers 221 - 226, wherein chamber 226 has a smaller diameter in the axial center than the remaining five chambers 221 - 225. Fig. 5 shows an anode pot 22 with seven chambers 221 - 227, all of which have the same diameter. Fig. 6 shows an anode pot 22 with only three chambers 221 - 223. The respective diameter of these three chambers 221 - 223 is larger than the respective diameter of the seven chambers 221 - 227 in the previous embodiment. Fig. 7 shows an anode pot 22 with three chambers 221 - 223. Here, however, one chamber 221 is designed with an oval diameter adapted to the curvature of the anode pot 22. The other two chambers 222 and 223, however, have a circular cross-section, as in the previous embodiments. In the Fig. 8In the anode pot 22 shown, two chambers 221, 222 are provided which are formed with mutually complementary semicircular cross sections. Fig. 9 finally shows an anode pot 22 with three chambers 221, 222 and 223, which are designed as separate complementary parts of a cylinder-like arrangement with a composite circular cross-section.

[0041] The Figures 10 and 11 show a schematic representation of a partial section of an anode 2' or 2" according to two further embodiments of the invention. These are special anode designs in which a so-called anode trough is already provided in the anode plateau during the manufacturing process. In a respective sectional representation, in the embodiment of the Fig. 10 the anode trough 14' has a square shape, in the embodiment of the Fig. 11 The anode trough 14" has a round shape.

[0042] The Figure 12shows a schematic representation of a longitudinal sectional view of an anode 20 according to another embodiment of the invention. Two chambers 221, 222 have the same diameter d 1.2 and the same shortest distance s 1.2 to the anode plateau plane 14. The third chamber 223, arranged in the longitudinal axis of the anode 20, has a larger diameter d 3 and a longer distance s 3 to the anode plateau plane 14.

[0043] The Figure 13 shows a schematic representation of a sectional view of an anode 200 according to a variant in which a chamber 221 is closed with an associated separate plug 266. To seal the plug 266, a solder wire coil 2661 is provided, which is circumferentially wound around the plug 266. Finally, the pot 22 of the anode 200 is closed with a lid 24, which also covers the plug 266 of the chamber 221.

[0044] Fig. 14shows a schematic view of an anode pot 220 with three chambers 221-223. Shown is the end face of the anode pot 220, onto which an anode cover is placed for firing and connected with solder (the latter is not shown here). The dashed lines 230 symbolize depressions in the base body of the anode pot 220, into which solder is filled in the form of small beads (the latter are not shown here).

[0045] The Figures 15 and 16 show in schematic representation the projection areas A1, A2, A3 of the cross-sectional areas of three chambers (not shown) on the respective anode plateau 14. As can be seen by comparing Fig. 15 with Fig. 16As can be seen, in both cases the projection areas A1, A2, and A3 are also shaped differently due to the differently shaped chambers. In both cases, however, the sum of the projection areas A1, A2, and A3 is noticeably smaller than the area of ​​the anode plateau 14, at least by a factor of 0.9.

[0046] The Figures 17A and 17B show a schematic representation of a top view and a longitudinal section along the longitudinal axis A of an anode 202 according to another embodiment of the invention. Here, four chambers K1-K4 are arranged one behind the other in the direction of the longitudinal axis A within the anode pot 22.

[0047] The Figure 18 shows a schematic representation of a plan view of a gas discharge lamp 10 according to an embodiment of the invention. The anode 2 corresponds to one of the Fig. 1 to 17shown embodiments of the invention. For details of the anode 2 not visible here, reference is made to the corresponding sections of the associated figure descriptions and the general description. For details on the further construction of the gas discharge lamp 10, reference is made to the corresponding description above.

[0048] The invention relates to an electrode, in particular an anode, for a gas discharge lamp, wherein the electrode has a base body enclosing a plurality of chambers. The chambers can be arranged parallel to one another or in series with respect to a longitudinal axis of the electrode and are at least partially filled with a low-melting metal, such as silver or copper. By suitably matching the number, filling, shape, and geometric dimensions of the individual chambers, as well as their position within the base body, to the respective design of the electrode, improved heat dissipation from the base body, in particular from the region near the anode plateau, can be achieved. LIST OF REFERENCE SYMBOLS

[0049] 1 Electrode (cathode) 2, 2', 2" Electrode (anode) 3 Cathode support rod 4 Anode support rod 5 Internal power supply (cathode) 6 Internal power supply (anode) 7 Discharge vessel 8, 9 Connection base 10 Discharge lamp 11 Cathode tip 12 Cylindrical area (cathode) 13 Cylindrical area (anode) 14 Anode plateau 14', 14" Anode trough 20 Electrode (anode) 200 Electrode (anode) 202 Electrode (anode) 22 Anode pot 220 Anode pot 221-227 Chamber 230 Recess 24 Cover 241 Hole 26 Silver 261-266 Plug 266 1 Solder wire coil

Claims

1. Electrode (1, 2) for a gas discharge lamp (10), wherein the electrode (1, 2) comprises a base body which encloses at least two chambers, wherein the chambers (221, 222) are hermetically, i.e. airtight or gas-tight sealed, characterized in that the chambers (221, 222, 223; K1 -K4) or at least part of the chambers are arranged in a longitudinal direction of the base body (22) in series or parallel to each other.

2. Electrode (2) according to one of the preceding claims, wherein the chambers (221, 222) or at least part of the chambers comprise a (partial) filling (26).

3. Electrode according to claim 2, wherein the filling (26) comprises one or more heat-conducting components.

4. Electrode according to claim 3, wherein the at least one heat-conducting component has a thermal conductivity that is greater than that of the base body.

5. Electrode according to claim 3 or 4, wherein the at least one heat-conducting component comprises one or more metals whose melting point is lower than the melting point of the base body of the electrode.

6. Electrode (2) according to one of the preceding claims, wherein the base body comprises a vessel part for example a pot (22), wherein the chambers (221, 222) are arranged in the vessel part (22).

7. Electrode (2, 20) according to claim 6, wherein the base body comprises a closure part for example a lid or plug (24, 261, 262) and wherein the closure part (24, 261, 262) closes the vessel part (22).

8. Electrode (2, 20) according to claim 7, wherein the closure part (24, 261, 262) closes the chambers (221, 222) hermetically.

9. Electrode (20) according to claim 6 or 7, wherein each chamber (221, 222) is hermetically sealed with a separate closure part for example a plug (261, 262).

10. Electrode (2, 20) according to one of claims 6 to 9, wherein the free end of the vessel part (22) is designed as an electrode plateau (14) on which the discharge arc starts during operation of the discharge lamp, and the closure part (24) or, if applicable, the sealing parts (261, 262) are arranged opposite the electrode plateau (14).

11. Electrode according to claim 10, wherein at least one chamber extends as close as possible to the electrode plateau without causing mechanical deformation of the electrode plateau.

12. Electrode according to any one of claims 6 to 11, wherein the sealing member or, if applicable, the sealing members are provided with a screw thread.

13. Electrode (200) according to any one of claims 6 to 12, wherein the sealing member (266) or, if applicable, the sealing parts are sealed with solder (2661).

14. Gas discharge lamp (10) with at least one electrode (1, 2) according to one of the preceding claims.