Device for generating a decoupled microwave plasma

Abstract

The invention relates to a device (1) for generating at least one decoupled microwave plasma (2) in a predetermined shape in a housing (3) having at least two opposite base sides (A, B) and a centre (Z) situated between the base sides (A, B) in the interior of the housing and an inlet for introducing a medium having a predetermined complex electrical conductivity into the housing, the device comprising at least one generator for generating microwave radiation, at least one antenna-shaped coupling-in unit (6), arranged at least partially within the housing (3), for coupling in the microwave radiation, wherein the at least one coupling-in unit (6) is arranged in such a way that the at least one coupling-in unit (6) faces the centre (Z) and is at a distance from the centre (Z). In this way, a device (1) is provided, by means of which, inter alia, a decoupled microwave plasma (2) having a very high energy density can be generated.

Description

[0001] Device for generating a decoupled microwave plasma

[0002] Technical area

[0003] The invention relates to a device for generating at least one decoupled microwave plasma in a cavity-shaped housing.

[0004] Furthermore, the invention relates to the use of the device for generating at least one decoupled microwave plasma, in particular in the form of a monopole antenna, and / or for generating at least one free-standing microwave plasma, in particular in the form of a dipole antenna.

[0005] Background of the invention

[0006] A decoupled plasma is a state in which the plasma is separated from its energy source and, in particular, occupies the volume of an antenna. In a normal plasma, the energy is supplied by an external source such as electrical discharges via electrodes or laser light, as well as radio-frequency radiation via waveguides, to ionize the atoms or molecules and maintain the plasma. In a decoupled plasma, however, the plasma is separated from the energy source and can obtain its energy over a longer free-space distance, such as by a laser beam directed at the plasma. Decoupled plasmas are used in various applications, such as materials processing, surface treatment, or research.

[0007] A decoupled plasma can be generated in several ways, depending on the specific application and the desired properties of the plasma. One method is microwave discharge. In this method, microwave radiation is coupled through a dielectric window or an internal antenna into a chamber containing the gas (at any desired pressure). The microwave energy ionizes the gas, creating a plasma that is separated from the energy source by the dielectric window or other microwave coupling. A plasma can be generated by various energy sources, such as electromagnetic signals.The difference between microwave plasmas (MW plasmas for short) and plasmas generated at lower frequencies is that the electrons absorb noticeable energy, since the heavy ions can hardly or not at all follow the fast alternating signal, especially above the plasma frequency, and that microwave energy can be transmitted through free space.

[0008] Conventional decoupled plasmas in the form of points or small spheres can be generated using high-power lasers. However, the laser light is increasingly reflected as the conductivity of the plasma increases, so the energy density of the plasma cannot be increased indefinitely.

[0009] Plasma torches have been in use for many decades. In the simplest form, they work with a waveguide and a quartz glass tube that is guided through this waveguide. Argon is preferably used as the process gas in the quartz glass tube, but other gases are also possible. These lamps can be operated at higher power levels, typically in the single-digit kW range, and in special designs, double-digit kW range. The resulting argon plasma does not have a high energy density, as the quartz glass diameter cannot be chosen too small and the plasma is generated in the center of the large, inaccessible waveguide and then blown out with losses. In these torches, just as in microwave plasma lamps, the energy is capacitively coupled through the quartz glass. The plasma is created directly behind the quartz glass wall. With decoupled plasma, however, there is a longer distance between a quartz glass window and the plasma area.In addition, the energy densities of torches are orders of magnitude lower than those of decoupled plasma.

[0010] Description of the invention

[0011] Based on this, the object of the invention is to provide a device with which a decoupled microwave plasma with a high energy density can be generated.

[0012] This object is achieved by the subject matter of patent claim 1. Preferred developments can be found in the subclaims. According to the invention, there is thus provided a device for generating at least one decoupled microwave plasma in a predetermined shape in a housing having at least two opposite base sides and a center located between the base sides in the interior of the housing and an inlet for introducing a medium with a predetermined complex electrical conductivity into the housing, the device comprising at least one generator for generating microwave radiation, at least one antenna-shaped coupling unit arranged at least partially within the housing for coupling in the microwave radiation, wherein the at least one coupling unit is arranged such that the at least one coupling unit faces the center and is spaced apart from the center.

[0013] In this context, "base sides" are understood to mean, in particular, two opposing base surfaces or base points of various geometries. If the housing is spherical, "base sides" are preferably understood to mean points. If the housing is cylindrical, "base sides" are preferably understood to mean surfaces.

[0014] When we speak of a "predetermined shape" of the plasma in this case, we mean, in particular, an antenna structure of any geometric shape. "Predetermined" is understood, in particular, to mean "known." This means that the shape is known and can be selected or adjusted depending on the structure, the energies, and the medium.

[0015] The at least one coupling unit is designed in particular as an electrical, magnetic or electromagnetic coupling unit.

[0016] It is therefore a key aspect of the invention that the microwave plasma is maintained and / or generated solely through the coupled microwave radiation. The microwave energy is coupled into the housing containing the medium. The microwave radiation interacts with the electrons in the medium and increases their energy, which leads to the ionization of the medium and generates a microwave plasma. The intensity, temperature, and other properties of the generated plasma are controlled by selecting the frequency and power of the microwave radiation, as well as the predetermined plasma antenna geometry.

[0017] In addition to dielectric windows, the coupling units preferably comprise cylindrical electrodes which, in particular in the case of coaxial supply, have an inner conductor preferably with an inlet for introducing a gas and preferably an outlet opposite the inlet for discharging the gas.

[0018] When we talk about "decoupled" in this case, we specifically mean that the microwave plasma is far away from the coupling unit compared to a plasma jet or plasma torch. Therefore, significantly higher power levels can be coupled in. The coupling unit acts as a remote antenna. The plasma energy is now only present where the processing area is located. This increases not only power tolerance but also efficiency.

[0019] The device can be used to generate a microwave plasma that is decoupled and / or freestanding. A freestanding microwave plasma is a plasma that is at least partially confined by preferably solid walls and can assume a predetermined shape within the at least partial housing.

[0020] When we refer to a "center" in this case, we don't necessarily mean the center of the housing, but rather a central point within the housing. The decoupled and / or free-standing microwave plasma is generated at this center and exhibits the highest energy density.

[0021] The term "base side" also refers to a "base point." This depends on the geometric shape of the housing.

[0022] According to a preferred development of the invention, the at least one coupling unit has an inner conductor for introducing a gas into the housing. Furthermore, the microwave radiation, in particular, can be fed into the housing through the inner conductor. A surrounding process gas can preferably be fed through a further inlet. According to a preferred development of the invention, the device has at least two coupling units, wherein the coupling units are each arranged symmetrically to the center. Preferably, the coupling units are arranged such that each coupling unit faces the center and is spaced from the center. With two coupling units, one coupling unit is arranged on a base side axially symmetrically to an axis running through the center. Alternatively, at least one, preferably several, coupling units are arranged laterally on the long sides between the base sides.The multiple coupling units are arranged such that they are directed toward the center where the microwave plasma is generated and maintained. This allows a microwave plasma with a very high energy density to be generated with the same microwave radiation or the same coupled microwave energy. This device can be operated via a push-pull signal from both ports or via just one port, provided the second port is short-circuited with a correct offset length. Calculations show that the magnetic field strength of the coupled microwave signal alone is sufficient to suppress the thermal expansion of the plasma. The energy density required to generate the fusion process can be achieved with an input power of 200 kW.

[0023] According to a preferred development of the invention, the housing, particularly for applications in the lower power range, at least partially comprises a screen grid. Alternatively, the housing preferably comprises small openings. The housing is preferably made of metal. A screen grid is used in plasma treatment to provide direct insight into the process. It consists of a grid or a perforated metal plate that is attached as a replacement for the metal wall of the housing. The screen grid fulfills several functions. Due to its identical shape to the closed housing, the screen grid prevents the energy source from coming into direct contact with the microwave plasma. This is important for controlling the properties of the plasma and avoiding undesirable effects such as overheating or damage to the energy source. Secondly, it controls the gas flow.The housing and / or the screen grid are specifically designed to control the gas flow in the (vacuum) chamber. Depending on the shape and / or position of the screen grid, a predetermined plasma shape is generated. A "predetermined plasma shape" is understood to mean a plasma shape that is explicitly desired for a specific application. Computer-aided simulations determine the relationship between the shape of the screen grid and the shape of the plasma, so that a (predetermined) plasma shape can be generated using a specifically shaped screen grid.

[0024] The arrangement of openings in the grid allows the gas flow to be evenly distributed, resulting in homogeneous plasma formation. Furthermore, the housing and the screen grid also serve as electrical insulation between the energy source and the microwave plasma. It prevents electrical currents or voltages from being directly transferred to the microwave plasma. As already explained, the screen grid and / or the housing can have different shapes and sizes depending on the application.

[0025] Both are often used in various types of plasma reactors, such as microwave plasma sources. In the latter case, however, they are only used to guide a waveguide mode. The housing is defined as the entire metallically enclosed space surrounding the plasma. The housing is preferably not divided into two parts by a dielectric barrier.

[0026] According to a preferred embodiment of the invention, the microwave radiation has a frequency in the high-frequency range, preferably between 0.2 GHz and 100 GHz, particularly preferably between 0.4 GHz and 20 GHz. At lower power levels, the signal is preferably amplified via a semiconductor power amplifier (e.g., a Class F amplifier and, if appropriate, a push-pull configuration). In electronics, a "push-pull configuration" refers to a special type of output circuit that is increasingly used in amplifiers or drivers. It is a symmetrical circuit in which two active components, such as two transistors, are used to amplify the signal both positively and negatively. In a push-pull signal, the input signal is split into two complementary signals, a positive signal and a negative signal, in the microwave range, particularly via a balun.These two signals are then amplified by separate transistors and then combined again to produce the amplified output signal. The advantages of a so-called push-pull signal are that it enables efficient use of power, suppresses instabilities and uses the energy of two transistors. While one of the transistors amplifies the positive signal, the other transistor amplifies the negative signal. When the signal changes polarity, the first transistor takes over amplification of the negative signal, while the second transistor amplifies the positive signal. In particular, through class F operation (alternatively, modes E and D may also be used), power loss is minimized and system efficiency is improved. Here, efficiencies of up to preferably 80% in the MHz range and 70% in the single-digit GHz range are achievable.

[0027] The semiconductor modules, which can be combined for low power outputs, can be used up to power levels in the double-digit kW range. Advantages include their service life, usable bandwidth, low maintenance, and stability.

[0028] Industrial magnetron sources have a significantly better efficiency of typically 88%, and are also inexpensive and very powerful.

[0029] According to a preferred development of the invention, the coupling unit further comprises a blocking device for pressure-tight arrangement of the coupling unit in the housing. By “pressure-tight arrangement” is meant in particular that the opening in the housing, through which the coupling unit is at least partially passed, so that it is at least partially arranged in the housing, is closed or blocked in a pressure-tight manner. The blocking device comprises in particular a hollow ceramic cylinder tube or a ceramic or quartz glass plate. In this way, a closed space is created in which either no gas exchange takes place (e.g. the air in the furnace) or the medium can penetrate. In the second case, the housing preferably also has an outlet for discharging the medium in addition to an inlet for introducing the medium. If the outlet is arranged upstream of the blocking device, the gas flow is preferably used to cool the assembly.If only or also the ceramic plate has holes, the gas flow is preferably used at least partially to enclose the plasma.

[0030] According to a preferred development of the invention, the medium comprises, in particular depending on the process, air, nitrogen, or a vacuum atmosphere. According to a preferred development of the invention, the gas comprises a noble gas, in particular argon, varigon, or helium. A distinction is made here between medium and gas. The "medium" is fed directly into the housing via the inlet of the housing and is understood as a protective gas. The present "gas" is fed into the housing via the inner conductor of the coupling unit and is understood as a process gas. According to a preferred development of the invention, a vacuum can be generated in the housing.

[0031] The process gas serves to simplify the generation, pre-shaping, and, if necessary, heating of the microwave plasma. It is introduced into the housing and ionized by the microwave energy. The choice of process gas depends on the desired type of plasma and the specific application. Preferably, the process gas is argon, varigon, or nitrogen.

[0032] The shielding gas or medium is used to protect the microwave plasma and its associated components from unwanted influences. It can be used to shield the microwave plasma from ambient air contamination or to protect sensitive materials from oxidation or damage during the plasma process. The shielding gas preferably comprises air, nitrogen, argon, or a vacuum atmosphere.

[0033] Selecting the right process and shielding gas is crucial for the quality and efficiency of the plasma process. Various factors must be considered, such as the desired chemical reaction in the plasma, the temperature resistance of the materials, and the purity of the gas. Careful selection and control of the gases is therefore essential to achieve optimal results in plasma technology.

[0034] According to a preferred development of the invention, a plurality of coupling units are designed such that the coupling units combine the microwave energy.

[0035] Preferably, the at least one coupling unit is designed to couple microwave radiation with a microwave energy between 0.2 kW and at least 200 kW. For power levels in the single-digit kW range, coaxial feeds from the generator into the housing are used, in particular. For power levels above the single-digit kW range, waveguides are used, in particular.

[0036] For applications as a plasma torch, emitter or jet, the housing preferably has an opening on a base side or base point through which the microwave plasma can escape, so that the microwave plasma can be used for processing like a laser beam.

[0037] According to the invention, there is further provided a method for generating a decoupled and possibly also free-standing microwave plasma with a device according to one of the preceding claims, with the following method steps:

[0038] 51) Pre-defining a predetermined plasma shape and estimating / analyzing the electromagnetic properties of the plasma,

[0039] 52) Performing a computer-aided simulation to determine a screen grid or all-metallic shape suitable for generating and maintaining a decoupled microwave plasma with the predetermined plasma shape,

[0040] 53) Producing the screen grid according to the determined screen grid shape and providing the screen grid for the device for generating a decoupled microwave plasma,

[0041] 54) Generating a decoupled and optionally also free-standing microwave plasma with the predetermined plasma shape by means of the device.

[0042] The decoupled plasma is thus generated in a predetermined plasma shape by adjusting the shape of the screen grid. Preferably, steps S1 to S4 are repeated if the energy coupling is still considered too low. In this way, the design or shape of the decoupled plasma can be optimized.

[0043] The invention further provides for the use of the above-described device for generating at least one decoupled microwave plasma, in particular in the form of a monopole antenna, and / or for generating at least one free-standing microwave plasma, in particular in the form of a dipole antenna or patch antenna. Furthermore, the device is preferably used for applications in the field of ion sources as well as fusion technology, in which the linear free-standing microwave plasma is reduced to a diameter in the range of 2 to 10 times the mean free path of the plasma purely by selecting a frequency above the plasma frequency and the magnetic fields of the radio-frequency signal.A further preferred use of the device is provided in which the spherical, decoupled microwave plasma is reduced purely by the magnetic fields of the radio-frequency signal to a diameter in the range of 10 to 50 times the mean free path of the plasma. For each coupling unit, the magnetic electromagnetic energy of the multiple input radio-frequency signals creates, in particular, a spherical, freestanding microwave plasma or a freestanding microwave plasma with a different antenna shape.

[0044] Alternatively, the spherical microwave plasma can also be used in fusion in combination with a laser. Such lasers have extremely short pulses with very high energy densities. Building up a plasma takes time. In this hybrid solution, the short pulse impinges on a built-up microwave plasma and, in contrast to pure laser generation, can raise this plasma to a much higher energy level.

[0045] Using approximately 200kW of input power, the device can be used as a small regional power plant based on the nuclear fusion principle, producing electricity in an environmentally friendly, constant, and extremely inexpensive manner.

[0046] The device is preferably used to generate freestanding plasmas with microwave energy between 0.2 kW and 500 kW for treating or processing materials in a furnace. Preferably, several freestanding plasmas are generated via several generators. These plasmas can be derived from a dipole antenna and thus have a linear shape. Alternatively, a flat plasma with a round or rectangular shape based on patch antennas is also possible. The plasma patch antennas can optimally heat the metallic or ceramic plate between the furnace and the heating area and thus implement the bottom and / or top heat furnace in a compact design. The invention also provides for the use of the device described above in a closed or continuous furnace.

[0047] Short description of the drawings

[0048] The invention is explained in more detail below using a preferred embodiment with reference to the drawings.

[0049] The drawings show

[0050] Fig. 1 shows a device for generating a decoupled plasma according to a preferred embodiment of the invention in a sectional view,

[0051] Fig. 2 a device for producing a decoupled and free-standing

[0052] Plasma according to another preferred embodiment of the invention in a sectional view,

[0053] Fig. 3 schematically shows an application example according to a preferred embodiment of the invention as a fusion application,

[0054] Fig. 4a, b schematically show an application example according to a preferred embodiment of the invention as a continuous furnace in the external representation,

[0055] Fig. 5 shows schematically an application example according to a preferred embodiment of the invention as a continuous furnace in the interior representation.

[0056] Fig. 6 schematically shows a method for generating a decoupled plasma according to a preferred embodiment of the invention. Detailed Description of the Embodiments

[0057] Fig. 1 schematically shows a device 1 for generating a decoupled microwave plasma 2 according to an embodiment of the invention. The device 1 consists of a housing 3. A coupling unit 6 is arranged in the housing 3. The coupling unit 6 comprises an inner conductor 7 with an inlet 8 and an outlet 10 through which a gas 9, such as the process gas, can be introduced to generate the microwave plasma.

[0058] The housing 3 also has an inlet 4 and an outlet 14 through which a medium 5, such as cooling air, can exit. The process gas can enter the housing 3 via 8 and circulate around the coupling unit 6. The area for the medium 5 is blocked off, if necessary, by the blocking device 12, which seals the space between the outlet 10 of the inner conductor and the inlet 4 of the medium 5. Alternatively, the blocking device 12 can also be gas-permeable and serve purely as a holder for the coupling unit 6.

[0059] Between the base side A and the base side B, a center Z is arranged, where the microwave plasma 2 is generated. The center Z is spaced from the outlet 10 of the inner conductor 7. Around the center Z, the housing 3 has a screen grid 11. The base side B is a simple metal plate on which the microwave plasma 2 is generated.

[0060] Fig. 1 schematically shows a 2.5D print head with which, for example, the lower metal plate B is coated using ceramic powder fed via 8.

[0061] In contrast to Fig. 1, Fig. 2 shows a structure of the device 1 for generating a decoupled, free-standing microwave plasma 2. The housing 3 is larger and comprises two coupling units 6A, 6B. The coupling units 6A, 6B are arranged symmetrically, with the output 10 of the inner conductor 7 directed toward the center Z, which is now located centrally. At the center Z, the gas 9 is now projected from two sides and irradiated with push-pull microwave radiation. This allows for a higher energy density and thus also a high-pressure region in the plasma.

[0062] Figure 1 shows that a decoupled microwave plasma 2 can be generated, while Figure 2 shows that a decoupled and freestanding microwave plasma 2 can be generated. The freestanding plasma has a very high energy density and can be used, among other things, as the basis for an ion source. It has been shown that, using the magnetic fields involved, a greater overpressure with a correspondingly high particle density can be generated in the freestanding plasma. The ions can be accelerated out of the plasma using conventional techniques using static high-voltage and magnetic fields.

[0063] Figure 3 shows the use of device 1 in a fusion device. A plurality of coupling units 6A-6F are arranged on or in the housing 3. All coupling units 6A-6F are pressure-tightly sealed with a locking device 12. The central coupling units 6A, 6B are the primary coupling units for plasma generation. The lateral coupling units 6C-6F are secondary coupling units, all of which are arranged axially symmetrically in the housing 3. The coupling unit 6A improves the symmetry when the signal is driven with a 180° phase shift relative to the signal at the coupling unit 6B.

[0064] These coupling units 6A, 6C, and 6E are all controlled with a calculated phase angle of X. The opposing coupling units 6B, 6D, and 6F require phase control of X+180° (a push-pull signal). The magnitude values ​​are all the same and can differ from the magnitude value of the central coupling unit 6A, 6B.

[0065] To further increase performance, additional coupling units installed in a circle can be used, all of which have the same phase and magnitude control within a circle, which usually differs from that of the other coupling units on the other circles (not shown here). The particularly ring-shaped shaped element 15 serves to geometrically optimize the plasma line of the decoupled and free-standing microwave plasma 2. The length will be around 1 cm at an operating frequency of 15 GHz. The diameter should be as small as possible. To optimize this diameter to be as small as possible over the entire length, the ring-shaped shaped element 15, which is made of the same surface material as the rest of the surface of the fusion chamber, serves to ensure that this diameter is as small as possible over the entire length. Tungsten is generally used here.

[0066] Figures 4a and 4b show the use of the device 1 in a continuous furnace. Figure 4a shows a perspective external view, and Figure 4b shows a schematic internal view. The continuous furnace consists of a conveyor belt 16 that runs through a furnace inlet 17, through the housing 3, and out of a furnace outlet 18, moving in the conveying direction F. The housing 3 is connected to a waveguide 19 and a generator 20 for generating microwave radiation.

[0067] Inside the continuous furnace, shown in Figure 4b, there are shaped elements 15 made of metal or ceramic for shaping the decoupled plasma 2, here in the form of a line plasma. The geometric shape of the shaped elements 15 is optimized using a program for the numerical calculation of electromagnetic field propagation and can have quite complex structures. This calculation process is referred to as "plasma shaping." The goods 21 to be heated are transported on the conveyor belt 16 and heated by the plasmas 2. Optionally, a metallic or ceramic plate, possibly perforated, is located between the freestanding plasmas 21 and the goods 21 to be heated.

[0068] Figure 5 shows the use of the device 1 in a plasma print head. For this purpose, the housing 3 has an opening 13 through which the decoupled and freestanding microwave plasma 2 is emitted and can be used as a plasma jet or plasma torch, or as a replacement for a laser.

[0069] Figure 6 shows the method for generating a decoupled microwave plasma 2 in a block diagram. In a first step S1, a desired or predetermined plasma shape is defined. The shape depends on the respective application. The plasma shape can, for example, be ring-shaped, spherical, or rod-shaped, as well as a grid square (patch antenna), ring, and many other shapes, each with different dimensions. Based on this predetermined plasma shape (which corresponds to a lossy microwave receiving antenna), in a second step S2, the shape of the screen grid 11, which is suitable for generating a decoupled plasma of the predetermined shape, is determined in a computer-aided simulation. It is important to carry out this method that an electromagnetic model of the microwave plasma is first generated and used in the simulation.Subsequently, in a third step S3, the screen grid 11 is created with the determined screen grid shape and installed in the device 1. This must be optimized using simulation so that as much microwave energy as possible is coupled into the plasma. In the final step S4, if necessary, the decoupled plasma 2 is then generated using the device 1 and the screen grid 11 specially manufactured for the respective plasma shape.

[0070] If the energy coupling is not yet satisfactory because the plasma model is inadequate for this operating case, the plasma can be measured at different input powers and a satisfactory model for the desired input power can be obtained by expanding the power-dependent modeling of the plasma. Steps S1 to S4 must then be repeated.

[0071] List of reference symbols

[0072] 1 Device for generating a decoupled microwave plasma

[0073] 2 decoupled microwave plasma

[0074] 3 housings

[0075] 4 Entrance

[0076] 5 Medium

[0077] 6 Coupling unit

[0078] 6A coupling unit

[0079] 6B coupling unit

[0080] 7 inner conductors

[0081] 8 Entrance

[0082] 9 Gas

[0083] 10 Exit

[0084] 11 Screen grid

[0085] 12 locking device

[0086] 13 Opening

[0087] 14 Outlet

[0088] 15 Formula em ent

[0089] 16 Conveyor belt

[0090] 17 Furnace entrance

[0091] 18 Furnace outlet

[0092] 19 waveguides

[0093] 20 generators

[0094] 21 goods to be heated

[0095] A base page

[0096] B Base side

[0097] Z Center

[0098] F Conveying direction

[0099] S1 Pre-defining a predetermined plasma shape and characterizing a plasma Performing a computer-aided simulation to determine a screen grid shape Creating the screen grid Creating a decoupled microwave plasma with the predetermined plasma shape

Claims

Patent claims 1. Device (1) for generating at least one decoupled microwave plasma (2) in a predetermined shape in a housing (3) having at least two opposite base sides (A, B) and a center (Z) located between the base sides (A, B) in the interior of the housing and an inlet for introducing a gaseous medium into the housing, the device comprising at least one generator for generating microwave radiation, at least one antenna-shaped coupling unit (6) arranged at least partially within the housing (3) for coupling in the microwave radiation, wherein the at least one coupling unit (6) is arranged such that the at least one coupling unit (6) faces the center (Z) and is spaced apart from the center (Z).

2. Device according to claim 1, wherein the at least one coupling unit has an inner conductor for introducing a gas into the housing.

3. Device (1) according to one of the preceding claims, comprising at least two coupling units (6A, 6B), wherein the coupling units (6A, 6B) are each arranged symmetrically to the center (Z).

4. Device (1) according to one of the preceding claims, wherein the housing (3) at least partially comprises a screen grid (11).

5. Device (1) according to one of the preceding claims, wherein the microwave radiation comprises a frequency in the high frequency range, preferably between 0.2 GHz and 100 GHz, particularly preferably between 0.4 GHz and 20 GHz.

6. Device (1) according to one of the preceding claims, further comprising a locking device (12) for each coupling unit (6) for pressure-tight arrangement of the coupling unit (6) in the housing (3).

7. Device (1) according to one of the preceding claims, wherein the medium (5) comprises air and / or nitrogen.

8. Device (1) according to claim 2, wherein the gas (9) comprises a noble gas, in particular argon.

9. Device (1) according to one of the preceding claims, wherein a vacuum can be generated in the housing (3).

10. Device (1) according to one of the preceding claims, wherein a plurality of coupling units (6) are designed such that the coupling units (6) combine the microwave energy.

11. Device (1) according to one of the preceding claims, wherein the at least one coupling unit (6) is designed to couple in microwave radiation with a microwave energy between 0.2 kW and at least 200 kW.

12. Method for generating a decoupled and optionally also free-standing microwave plasma (2) with a device (1) according to one of the preceding claims, with the following method steps: 51) Pre-defining a predetermined plasma shape and estimating / analyzing the electromagnetic properties of the plasma, 52) Carrying out a computer-aided simulation to determine a screen grid or all-metallic shape (11) suitable for generating and maintaining a decoupled microwave plasma (2) with the predetermined plasma shape, 53) producing the screen grid (11) according to the determined screen grid shape and providing the screen grid (11) for the device (1) for generating a decoupled microwave plasma (2), 54) Generating a decoupled and optionally also free-standing microwave plasma (2) with the predetermined plasma shape by means of the device (1).

13. Use of the device (1) according to one of claims 1 to 12 for generating at least one decoupled microwave plasma (2), in particular in the form of a monopole antenna, and / or for generating at least one free-standing microwave plasma (2'), in particular in the form of a dipole, spherical or patch antenna.

14. Use of the device (1) according to one of claims 1 to 12 in a fusion plant and / or ion source and / or in a standard furnace and / or continuous furnace and / or plasma emitter and / or plasma jet and / or plasma torch, and / or in a plasma print head.

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