EP0468990A1

EP0468990A1 - Generation of a high-frequency field in a useful volume

Info

Publication number: EP0468990A1
Application number: EP19900905516
Authority: EP
Inventors: Wolfgang Krüger
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1989-04-17
Filing date: 1990-04-10
Publication date: 1992-02-05
Also published as: JPH04504640A; WO1990013151A1; DE3912569A1

Abstract

Il s'agit de coupler dans des espaces utiles, de préférence de forme allongée dans un seul sens, des champs à haute fréquence dont résulte, le cas échéant, une distribution voulue de la puissance HF dans un milieu absorbant introduit dans ledit espace utile. On y parvient soit en en provoquant dans le plus grand allongement de l'espace utile une longueur d'onde de De Broglie qui atteint approximativement ou dépasse l'allongement de l'espace utile (1), soit en provoquant dans cette direction une onde amortie apériodique, la puissance HF étant couplée dans l'espace utile, suivant l'allure de champ désirée, aussi perpendiculairement que nécessaire à la direction de l'allongement. Dans le dispositif y afférent comportant un espace utile de forme linéaire, l'espace utile (1) se trouve à l'intérieur d'un espace d'accouplement (2) qui présente sur toute sa longueur au moins une paroi de couplage (30, 30') avec des ouvertures de couplage (31 à 34) pour la distribution de la puissance HF et qui est alimenté depuis un espace de distribution (40, 40').It is a question of coupling in useful spaces, preferably of elongated shape in only one direction, fields with high frequency from which results, if necessary, a desired distribution of the HF power in an absorbent medium introduced in said useful space. This is achieved either by causing a De Broglie wavelength which approximates or exceeds the lengthening of the useful space (1) in the greatest extension of the usable space, or by causing a wave in this direction aperiodic damping, the HF power being coupled in the useful space, according to the desired field appearance, as perpendicular as necessary to the direction of the elongation. In the related device comprising a useful space of linear shape, the useful space (1) is located inside a coupling space (2) which has over its entire length at least one coupling wall (30 , 30 ') with coupling openings (31 to 34) for the distribution of HF power and which is supplied from a distribution space (40, 40').

Description

Generation of an electrical high-frequency field in a usable space.

The invention relates to a method and a device for generating an electrical high-frequency field according to claim 1 and claim 14, respectively. A desired field strength profile within a usable space that has dimensions that are significantly larger in one direction than in the other two directions, be generated. In addition, a desired distribution of HF power to a lossy medium that is introduced into the usable space is also to be achieved.

For a number of physical or technical applications, it is necessary to generate high-frequency field or power distributions in those utility rooms in which one or two linear dimensions are greater than approximately 1/10 of the HF free space wavelength. It is known that, for example, a usable space can be achieved in a rectangular waveguide with a suitable width, which has a largely uniform local distribution of the electric field strength, but can be considerably longer than it corresponds to a multiple of the free space wavelength at the frequency used .

For the latter purpose, for example, the cross section of a

The waveguide is chosen so that at the frequency determined by the HF generator, the wave type of the lowest frequency ("basic type") with a high phase wavelength propagates in the waveguide or forms a standing wave. Part of this standing wave can then be used to generate a uniform field configuration. In this way, however, it is not possible to achieve a uniform power density distribution in a strongly absorbing medium, since the damping in the direction of propagation of the wave causes a sharp drop in the field strength and the power density.

This problem occurs, for example, with CO ₂ and CO lasers that are excited with a frequency in the microwave range. In these, the plasma tube usually has a length which is a multiple of the free space wavelength of the generator frequency. Up to now, technically satisfactory results have only been provided by so-called “fast flow” lasers, in which areas with very different HF current density act on the plasma due to a high gas throughput in the longitudinal direction and the various strongly excited areas of the plasma volume also rapidly ¬ are swirled together. For example, such a type of laser is described in DE-OS 37 43 258.

In the case of the previously known diffusion-cooled, microwave-excited designs of lasers, on the other hand, local irregularities and / or temporal fluctuations in the excitation occur which cannot be compensated for and are therefore disadvantageous for the technical application of such arrangements.

To avoid these disadvantages, it has hitherto been necessary to supply the application power at a frequency which is so low that the corresponding free space wavelength 2 is considerably greater than the length of the laser-active plasma volume. This also applies to HF-excited stripline lasers.

In this embodiment of a laser, the plasma is produced between two elongated plates made of metal or a dielectric, which are a few millimeters apart and oppose each other. These plates also serve as electrodes for excitation of the plasma and as waveguides for guiding the laser beam in the resonator. In the case of plates which consist of a dielectric, the RF power can be guided via guide segments segmented along the plasma zone. Vouchers are supplied in several places, which however results in discrepancies in the suggestion.

Embodiments of such stripline lasers are described in detail, for example, in DE-OS 37 29 053 and EP-A-0 275 023.

In contrast, the object of the invention is to specify a method and the associated device, by means of which, for example, a high-frequency field with a desired local field profile, preferably a uniform field, can be generated in a spatially stretched useful space. Such a method and the associated device should also allow RF power with a desired, in particular uniform, local course to be distributed to a lossy medium introduced into the usable space. Such a method should be suitable for a wide variety of applications, for example also for CO ₂ lasers.

The object is achieved by a method according to the features of claim 1. Further developments and specific applications of the invention result from the dependent method claims. This method is implemented with a device according to the independent device claim, further developments being specified in the dependent subclaims.

According to the invention, the vector of the electric field strength for the HF power coupled into the useful space is largely perpendicular to the surfaces of the useful space determined by the two larger dimensions. Of the length dimensions that characterize the usable space, at least one is larger than the other two or exactly as large as one of the other. At least one of the two major lengths is in this case greater than 1/10 of the freirurt wavelength, which corresponds to the frequency of the coupled power, the direction of the power flow into the useful space largely forming a right angle with the directions of the longitudinal dimensions. -

In the context of the inventive teaching, it is proposed to include the usable space in a structure in the manner of a waveguide. It is dimensioned such that at a specific excitation frequency f the phase wavelength becomes so large at least in one direction, in particular the longitudinal direction, that it comes close to the greatest length dimension of the usable space or that it exceeds this dimension. Alternatively, the structure can be dimensioned such that the phase wavelength becomes computationally imaginary at the excitation frequency. In this case there is an aperiodically damped waveguide.

In the solution according to the invention, the dimensioning of the coupling space surrounding the usable space is defined in the manner of a waveguide by theoretically specifying the phase wavelength in the direction of at least one of the two larger length extinctions. It is, however, characteristic of the invention that the HF power is supplied to the useful space not from the ends or from a single point, but essentially from ¹ or more of the long sides and distributed over them. For this purpose, these sides are provided with so-called "coupling walls" with coupling openings. The coupled-in power can be taken in a simple manner from a correspondingly designed waveguide structure which, as a divider space, has similar limit dimensions with respect to the phase wavelength over at least part of its length as the coupling space. In this distribution space, the power can be applied in a known manner by means of a waveguide, by means of a coupling pin or coupling loop of a coaxial line transition or directly with the coupling pin of a magnetron. be fed.

With a corresponding design of the device, the method according to the invention is suitable for a wide variety of technical applications. These include, for example, spectroscopic observation and the generation or decomposition of gases, vapors or liquids of a certain composition, as well as the treatment of surfaces of solid substances or the deposition of layers on substrates or on the surfaces serving as electrodes themselves the invention advantageously suitable for generating electromagnetic radiation by excitation of a gas plasma, in particular in gas lasers and preferably in stripline lasers.

Further details and advantages of the invention result from the following description of the figures of exemplary embodiments. 1 shows the principle of the invention with the field strength profile in both directions, FIGS. 2 to 4 different cross-sections of the coupling space according to FIG. 1 with a tube therein, the interior of which serves as a useful space, FIG. 5 shows the design of the coupling space according to Art a ridge waveguide with the inner volume of an inserted tube as usable space,

6 shows the arrangement of two tubes pushed into one another, the space between them forming a cooling channel, FIG. 6 shows another embodiment of the cooling channel, FIG. 8 shows an embodiment example suitable for a laser application with one-sided coupling of the RF power into the coupling space, FIG. 9 shows another embodiment a double-sided coupling of the RF power and FIG. 10 the assignment of the field strength profile in the transverse direction of the useful space with the associated structure of the coupling space. 1 In the figures, identical or identical parts are denoted by the same reference symbols. Some of the figures are described together «

In FIG. 1, a useful space 1, in which the desired field distribution is to be generated or in which the RF power with a certain field distribution is to be supplied to a medium, is electrically connected to a coupling space 2. The coupling space is delimited along the sides by a boundary 15.

10 closed or provided with a coupling wall 30 through which the RF power, which is required to cover losses or to treat the medium, enters from a distribution space 40 with a suitable power density distribution. The flow of power is indicated by arrows.

15

The purpose of the distribution space 40 is to supply the signals from a generator 46, for example a magnetron, with the frequency f and the associated free space wavelength λ and, for example, via a waveguide or a cable 44 and a transmission cable.

20 aisle 45 or to distribute the power supplied directly from the coupling pin of the magnetrons along the coupling wall 30. In particular, if only little or very much power is consumed in the useful space 1, standing waves or uneven resonance peaks can occur due to the occurrence of standing waves

25 desired course of the field strength or power density in the

Often only achieve usable space 1 if the coupling space 2, the coupling wall 30 and the distributor space 40 are carefully dimensioned. The exact calculation of such an arrangement is then comparatively complex.

^ 30

Suitable cross-sectional dimensions of the coupling space 2 can be calculated by an approximation sufficient for many purposes if there are media in the useful space, their relative dielectric constant - has a real part f ', between 0.7 and 3 and - an imaginary part £ "-_ between 0.05 and 0.2. A real part l _e * ι <1 occurs, for example, in the case of piezoelectric materials in the vicinity of mechanical ones Resonances as well as with plasmas.

The approximate calculation of the cross-section of the coupling space and usable space is carried out as follows:

It is initially assumed that the coupling wall 30 is replaced by a continuously conductive wall, which, however, has moved outwards by 5% of the wavelength 3, and that the usable space 1 is free of the medium to which the HF power is supplied shall be. The cross-sectional dimensions of the coupling space 2 are then to be selected such that only a weakly aperiodically damped wave can propagate in the longitudinal direction in the z direction at a certain frequency f _ß or a wave whose phase wavelength _{p is} at least 1.5 times the free space wavelength ₀ the generator frequency is f.

In the event that the power is fed into the coupling space 2 from only one side, the following applies with the excitation frequency f for the calculation frequency f _ß : ^f B * ^f o '

The distribution space can be dimensioned according to the same principle, the disturbance caused by the coupling point for the HF power not having any significant effect. In general, special measures are expedient in the vicinity of the point or the points at which the ΗF power is supplied by the generator 46, on the one hand to improve the adaptation, and on the other hand the effect of the field disturbance at the supply point on the closest areas of the To prevent coupling wall 30. Such a measure can, for example, in the reduction of coupling openings in this area or in the interposition of another distribution room with coupling wall.

If the RF power is fed into the coupling space 2 from two sides and the option is made to make the useful space 2 wider than is possible with one-sided coupling of the RF power, the following applies: f _B (0, 6 ... 0.9). f _Q , the smaller factor being assigned to a larger width of the usable space 2.

A particular advantage of the method according to the application is that with a suitable dimensioning of distribution space 40, coupling wall 30 and coupling space 2, the risk of instabilities in the power distribution in the medium can be reduced. If, for example, the conductivity of the medium rises rapidly at a point when a critical temperature, field strength or power density is exceeded, in many arrangements used to date a considerable part of the total power is concentrated on this point and increases the instability.

In the method specified according to the invention, the power is transported in the longitudinal direction of the usable space, i.e. the z-direction according to FIG. 1. Right across, i.e. 1 in the x-direction according to FIG. 1, the increased power consumption compared to the neighboring areas due to the properties of the coupling space in the transverse direction can lead to a mismatch in the area of the nearest coupling openings and also reduce the power supply in this direction .

FIG. 1 also shows the course of the field strength E with a desired largely uniform power density distribution over the width (x direction) and the length (z direction) of the useful space 1 with the length L is shown as a solid line. The field course outside the useful space 1 is indicated by broken lines, taking into account the effect of parts made of dielectric material at the ends of the useful space 1 in the z direction, which leads to a rapid drop in the electric field strength E. The HF power fed in by the generator 46 in the middle of one narrow side of the distributor space 40 leads to the sketched field profile. It enters the coupling space 2 largely uniformly through the openings 31 of the coupling wall 30. The useful space 1 is expediently arranged in the area of the maximum of the field strength E in the coupling space 2, so that the unevenness of the field strength E remains low in the transverse direction.

As mentioned, remaining non-uniformities in the field strength and wall current distribution in the distribution space 40 along the coupling wall 30 do not have to lead to an uneven power distribution in the coupling space 2 and useful space 1, if due to different size or shape and / or position of individual coupling openings compensation is created. In particular, if the usable space of a particular arrangement is to be suitable for different media with very different dielectric constants and corresponding losses, it can be expedient to arrange a plurality of distributor spaces side by side in the x direction and to separate them in each case by coupling walls. These distribution spaces can be designed symmetrically or asymmetrically with different cross-sectional shapes, such as, for example, rectangular waveguides, ridge waveguides and ridge waveguides with several ridges. When using the method for lasers, the reliable ignition of the laser gas and the operation over a larger range of the gas pressure and the electrode spacing as well as the operation within a larger power range can be realized by these measures. Overall, FIG. 1 shows the course of the field strength E in the entire coupling space 2, corresponding to a disturbed sinus distribution. In the area of the maximum of the field strength E ,, the useful space can be determined so that the non-uniformity of the field strength distribution or the power distribution in the medium becomes a minimum. The same also applies to the longitudinal direction in the useful space 1. As already mentioned, the steep drop at the ends of the curve is carried out in the same way as in the distributor space 40 by special measures in the end regions. Such measures are, for example, the introduction of parts made of dielectrics or conductive substances, cross-sectional widenings or the insertion or addition of waveguide pieces which act as a resonator.

This results in a largely uniform field strength or power density profile in the longitudinal direction in the useful space 1, which has not previously been achieved in this form. In the prior art, for utility rooms whose longitudinal extent reaches or exceeds about half the free space wavelength 2 _{Q of} the fed-in HF power, the power flow either locally too discontinuously or almost entirely in the longitudinal direction, so that from physical Inevitably, a very uniform field or power distribution could not be achieved for reasons.

In FIGS. 2 to 4, the coupling space 2 each contains a tube 50, for example made of ceramic, the inner volume of which can be used as a useful space 1 for a wide variety of applications. Specifically in FIG. 2, only one of the two side walls of the coupling space 2 is designed as a coupling wall 30, through whose openings 31 and 32 the HF power is supplied. The other side wall 15 is closed, but can also be provided with small openings which are suitable for optical observation, for irradiation of UV light as an ignition aid or for similar purposes, the through the opposite coupling wall fed RF power can only pass through to an insignificant extent.

In Figure 3, both side walls are designed as coupling walls 30 and 30 ', so that RF power can be fed in from both sides. The special possibility here is discussed further below for specific application purposes.

In FIG. 4, the coupling space forms a T-structure, in the center of which there is the tube 50 with the useful space 1. The web at the base of the T forms the coupling wall 30 with coupling openings 33, while the webs on the T-beam form the associated short-circuit walls 15. For better performance adjustment of the medium located in the useful space 1 to the field conditions in the coupling area 2 it may also be advantageous here to arrange the short-circuit walls 15 and 15 'and the coupling wall 30 at different distances from the tube 50.

The coupling spaces 2 in FIGS. 2 to 4 are designed in the manner of rectangular waveguides; there are also possible designs in the form of ridge waveguides, as will be shown below. In particular, the webs 22 and 23 on the wide walls 10 and 20 can be flat and with their opposite surfaces 11 and 21 are parallel to each other.

When the RF power is coupled into the coupling space 2 on one side, it may be advantageous not to arrange the useful space 1 centrally between the coupling wall 30 and the short-circuit wall 15, in order in this way to achieve a uniform field profile in the transverse direction of the useful space 1 or one to obtain favorable performance adaptation of a medium in the tube 50 to the field conditions in the coupling space 2.

In further exemplary embodiments, 12 of the desired specific field distributions of the coupling space 2 can be formed in a star shape in cross section with the same or different lengths of the individual radiation-like parts. The distance of the short-circuit walls 15 or one or more coupling walls 30 from the longitudinal axis of the useful space 1 can thus be varied.

In FIG. 5, a waveguide structure 20 is shown as a coupling space, in which webs 12 and 22 are provided for adapting to the cross-section of a tubular container 50 with its inner volume as a useful space 1, which have a curved, for example, on the tube 50 matched area. The webs 12 and 22 advantageously contain cooling channels 54 and 55 through which a cooling liquid or a cooling gas flows. The coupling space 20 can form a uniform structure with the coupling wall 30 and the distributor space 40.

A further tube 51 made of electrically active material can be arranged in the tube 50 according to FIG. 5, as is indicated in FIG. 6. With suitable dimensioning, this can bring about an additional homogenization of the field in usable space 1. The space between the tubes 50 and 51 can be flowed through with a low-loss coolant for cooling purposes.

In FIG. 7 it is further shown that by dividing the intermediate space between the two tubes, separate cooling lines are formed. As a result, water can also be used as the cooling liquid under certain conditions, without a significant absorption of the HF power taking place therein.

The coupling walls 30 can have the following different structures with their coupling openings 31. For example, slots, round or rectangular holes or a combination thereof are possible. In particular, slots can also be arranged in a row in a row against one another, or else the slots run zigzag. Combinations of slots with holes are also possible, for example in the form of dumbbell structures. Webs can also be used as coupling means, which are alternately pressed out of the plane of the coupling wall 30 in the direction of the coupling space 2 or the distribution space 40, or, if appropriate, also so-called coupling loops.

A metal wall with a long, continuous longitudinal slot can also serve as the coupling wall 30. Coupling wall in the aforementioned sense is also to be understood as other devices which have the function of an electromagnetic coupling between the distribution space and the coupling space, such as e.g. Pieces of low rectangular waveguides that can be filled with a dielectric.

The tube 50 with its internal volume as the useful space 1 according to FIGS. 2 to 5 can have sealable accesses at both ends, via which a medium can be inserted or removed. Such a medium can be, for example, a gas or gas mixture which is to be excited for the analysis or emission of laser radiation or in which certain decomposition or connection processes are to take place. To support the latter processes, catalytically active substances can be present in the usable space, for example in the form of layers on the walls.

Furthermore, it is possible to introduce substrates into the tube 50, the surfaces of which are to be influenced, for example, by plasma etching, or on which layers are to be deposited. With a suitable design, such a substrate can advantageously continuously run through the useful space 1. Such layers can also be deposited uniformly on the boundary walls of the useful space 1 itself, that is to say, for example, on the inner tube wall or the opposing inner surfaces 11, 21 of webs 12, 22. 14 In Figure 8 and Figure 9, the groove ^is' 1 zraum directly formed by the space between opposing surfaces 11 and 21 of two webs 12 and 22 of wall parts 10 and 20th This design in the manner of a ridge waveguide can be used in particular for a ribbon conductor gas laser. On one side there is an end wall 15 and on the other side there is the coupling wall 30 which, according to FIG. 1, is connected to a distributor space 40 for HF power and has coupling openings 31.

In FIG. 1 and FIG. 8, the width of the useful space 1 is limited by the requirement for uniformity of the electric field in the transverse direction. Certain widths cannot be exceeded with this arrangement unless a higher unevenness in the field course in the transverse direction can be accepted. If a uniform field profile over a larger width is required, then as already shown in principle in FIG. 3, there is the advantageous possibility of feeding the RF power from two sides into the coupling space 2, which corresponds to FIG. 8 for the laser application in FIG. 9 is also formed by the space between the band electrodes 10 and 20.

FIG. 10 shows the course of the field strength E y for the embodiment according to FIG. 9. Such a course occurs when a lossy medium is brought into the useful space and the RF power enters the coupling space 2 in phase from the distribution spaces 40 or 40 'through the openings of the coupling walls 30 or 30'.

The wall parts 10 and 20 shown in FIGS. 8, 9 and 10 with the webs 12 and 22 need not be made of a uniform material. In particular, the surfaces 11 and 21 of the webs 10 and 20 can be provided with optically, chemically, physically or mechanically effective coatings as required. The abrasion and sputter resistance can preferably be improved by an aluminum oxide or boron nitride coating; The optical properties of layers made of germanium and silicon and their oxides, made of aluminum oxides and gold, are particularly advantageous in the case of CO 2 -band conductor and waveguide lasers, the latter two materials also counteracting the disruptive CO ₂ decomposition.

Different gases or gas mixtures tend to undesirably form arcs in certain pressure areas when the plasma is excited between metal electrodes instead of the desired glow discharges. Instabilities can also be promoted which cannot be sufficiently suppressed by the coupling of the RF power described in detail according to the invention. In such cases, the regions of a web or both webs 12 and 22 facing the usable space are advantageously produced at a height of up to a few millimeters from dielectric material, preferably a ceramic material with good thermal conductivity and a low relative dielectric constant, which is good is heat-conducting and bubble-free connected to the metallic part of the walls 10, 20 or the webs 12, 22. The desired stabilizing effect, which suppresses an arc discharge, essentially arises from the fact that, with a suitable choice of the dielectric constant and the thickness of such plate supports, this counteracts a local current increase, as occurs, for example, during arcing, as a capacitive series resistor, in that the electric field strength decreases at this point.

When feeding the RF power according to FIG. 9 from both sides into the coupling space, there are several possibilities: On the one hand, the feed can be phase-locked in amplitude and phase. This can be done, for example, by dividing the power of a single generator into one 3 dB branching or by using two phase-locked coupled generators. In addition, two generators can be used that are not coupled and do not synchronize with each other. In this case, an RF field strength that fluctuates over time with the difference frequency of the generators results in the useful space. This can be permitted for various applications if the difference frequency is high enough. Finally, two generators can be alternately keyed so that one generator emits a power pulse while the other is blocked. Such a mode of operation is also permissible or even desirable for many applications, for example the excitation of a laser plasma.

In all of the exemplary embodiments described, it is possible in a simple manner to distribute RF power largely evenly in the microwave region over coupling walls in a desired manner over a usable space, the length of which can be up to approximately 6 times the free space wavelength Λ. If longer usable spaces are required, then several distributor spaces, each with a generator, can be joined together on one or both sides along the coupling space. If - as in many applications - it is permissible to supply the RF power in a pulsed manner, it can be advantageous to operate the generators with the same pulse frequency, but with time-shifted pulses, in such a way that adjacent or opposite distribution spaces are not used RF power is applied at the same time.

Claims

1. A method for generating an electrical high-frequency field with the desired field strength profile in a usable space (1), which is preferably extended in one direction, and / or a method for distributing the RF power in a lossy medium that is introduced into the usable space (1), with the following features:

- In the greatest longitudinal extent of the useful space (1) a phase wavelength is forced for the coupled RF power, which is close to the longitudinal extent of the useful space (L) or above, or an aperiodically damped wave in this direction forced

- The high-frequency power is largely perpendicular to the desired field profile in the useful space (1)

Coupled in the direction of its longitudinal extent.

2. The method according to claim 1, characterized in that the high-frequency power which is to be implemented in the useful space (1) is first supplied to a distribution space (2) by a generator predetermined generator ^" requenz (f)" ., which is connected via a coupling wall (30) to a coupling space (2) for the useful space (1).

3. The method of claim 2, d a d u r c h g e k e n n ¬ z e i c h n e t that in the useful space (1) in its longitudinal direction results in a phase wavelength that is greater than approximately 1.3 times the free space wavelength (X) of the injected

RF power at the generator frequency (f _Q ).

4. The method according to claim 2, characterized in that the phase wavelength in the longitudinal direction of the useful space (1) goes against ^* = ^> °.

5. The method according to claim 3, so that the longitudinal extent of the usable space (1) is at least one tenth of the free space wavelength (L> _ 1/101).

6. The method of claim 1 or claim 5, d a d u r c h g e k e n n z e i c h n e t that a generator frequency (f) in the GHz range, corresponding to a free space wavelength () in the microwave range, is selected.

7. The method of claim 4, d a d u r c h g e k e n n ¬ z e i c h n e t that the generator frequency is 2.45 GHz.

8. The method according to any one of the preceding claims, g e ¬ k e n n z e i c h n e t by the application for the synthesis of gases.

9. The method according to any one of the preceding claims, g e - k e n n z e i c h n e t by the application for the decomposition of

Gases.

10. The method according to any one of the preceding claims, by the application for changing surfaces of substrates, in particular for plasma etching.

11. The method according to any one of the preceding claims, g e ¬ k e n n z e i c h n e t by the application for the deposition of layers on substrates, in particular on a continuously lent through the usable belt.

12. The method according to any one of claims 10 or 11, d a ¬ d u r c h g e k e n n z e i c h n e t that boundary surfaces of the useful space (1) itself serve as substrates.

1 13. The method according to any one of the preceding claims, ge ¬ indicates the application for Plasmaanre¬ excitation in gas lasers, preferably stripline lasers.

14 device for carrying out the method according to claim 1 or one of claims 2 to 13, with a usable space which is preferably extended in one direction, characterized in that the usable space (1) and, if appropriate, a container delimiting the usable space (1) (50) yourself

10 are located within a coupling space (2) or are part of a coupling space (2, 10, 20) which has a coupling wall (30, 30 ') over almost its entire longitudinal extent, at least on one side, which is provided with coupling openings (31 to 34) is, RF through the coupling openings (31 to 34)

15 power from at least one distributor space (40) is fed into the coupling space (2).

15. The apparatus of claim 14, d a d u r c h g e ¬ k e n n z e i c h n e t that the coupling wall (30, 30 ') of

20 one or more low waveguide pieces is formed, which are connected to parts made of dielectric material.

16. The apparatus of claim 14, d a d u r c h g e -

25 k e n n z e i c h n e t that the useful space (1) is enclosed by a tube (50) which is located within the coupling space (2).

17. The apparatus of claim 16, d a d u r c h g e -

^~ 30 indicates that the tube (50) delimiting the useful space (1) is surrounded by another tube (51) at a predetermined distance to form an intermediate space (52), and that the intermediate space (52) or parts ( 56, 57) of the intermediate space are flowed through by a cooling medium. 35

18. The apparatus according to claim 14, dadurchge ¬ indicates that the usable space (1) of mutually opposite surfaces (11, 21) of two wall parts (10, 20) or two as webs (12, 22) formed projections of the wall parts (10, 20th ) is limited as a coupling space.

19. The apparatus according to claim 18, dadurchge ¬ indicates that the webs (12, 22) are covered with plates made of ceramic or glass-like material and that the thickness of the plate-shaped material is chosen depending on its relative dielectric constant so that one for each unit area capacitive resistance between the metallic part of the web (12, 21) or the wall part (10, 20) and the useful space (1) is achieved.

20. The apparatus of claim 18 or 19, so that the opposite surfaces (11, 21) of the wall parts (10, 20) or the webs (12, 22) - are provided with coatings.

21. Apparatus according to claim 18, 19 or 20, so that the wall parts (10, 20) or webs (12, 22) with the surfaces (11, 21) are part of a stripline laser.

22. The apparatus of claim 14, d a d u r c h g e ¬ k e n n z e i c h n e t that there is a gas or vapor plasma in the usable space (1). located.

23. The device according to claim 15 and 17 to 21, characterized in that the wall parts (10, 20) or their webs (12, 22) with channels (54, 55) are ve.rsehen which are flowed through by a cooling medium.

24. The device according to claim 23, so that the wall parts (10, 20) are thermally connected to an external cooling device.

25. The device according to claim 14 and 17 to 22, characterized in that between the upper and lower wall parts (10, 20) of the coupling space (2) or the distribution space (40) delimiting parts made of a low-loss material, for example a side wall (15), are inserted, which prevent the escape of the medium located in the usable space.

26. The apparatus according to claim 14, dadurchge ¬ indicates that the side wall (15) and the coupling wall (30) close the coupling space (2) vacuum-tight and that the coupling openings (31 to 34) with parts made of a low-loss material, preferably glass, quartz or ceramic, are sealed vacuum-tight.

27. The apparatus according to claim 14, so that the coupling wall (30, 30 ') and coupling openings (31 to 34) are provided with parts made of metal and / or dielectric material in order to obtain the required coupling properties.

28. The apparatus of claim 14, d a d u r c h g e ¬ k e n n z e i c h n e t that the distribution space (40) is connected directly or via cable, waveguide, connectors and transition pieces with an RF generator (46), such as a magnetron.

29. The device according to claim 14, dadurchge ¬ indicates that the coupling space (2) and the distributor space (40) are shaped in cross section in the manner of a rectangular or ridge waveguide. 30. The device according to claim 14, dadurchge ¬ indicates that two or more distribution spaces (40, 40 ') by coupling walls (30,

30 ') are separated from one another with coupling openings (31) and are arranged in parallel next to one another.

31. The apparatus according to claim 14, dadurchge ¬ indicates that to achieve long useful spaces (1) along a coupling space (2) of appropriate length, several distribution spaces (40) on one or both sides of the useful space (1) are arranged, each with a generator (46) are connected and feed RF power into the coupling space (2) via coupling walls.

32. Apparatus according to claim 14, so that several HF generators are present which pulse their power and emit at the same pulse frequency, the pulses taking place simultaneously or at different times.