DE102021128964B3 - Process and device for generating plasmas with increased pulse energy by means of dielectrically impeded electrical discharges - Google Patents

Abstract

In a method for generating plasmas through dielectric barrier electrical discharges (12), a charge collecting element made of electrically conductive material (15) is arranged on a flat outer surface (5) of a dielectric shielding (3) of an electrode (2). The charge collecting element (14) has an electrically conductive collecting area (20) of at least 1 mm ² along the outer surface (5), a small aspect ratio and a maximum diameter of 10 mm. The collection surface (20) is much smaller than an electrode surface (19) of the electrode (2) lying behind it. At most, the charge collecting element (14) protrudes slightly beyond the outer surface (5). The outer surface (5) is arranged parallel to an object surface (7) to be treated at a minimum free distance (6) between 0.5 mm and 20 mm. A changing voltage is applied to the electrode (2) in order to produce dielectrically impeded electrical discharges (12) in a working gas between the outer surface (5) and the object surface (7), a discharge filament (13) being emitted from the charge-collecting element (14). with increased pulse energy.

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates to a method for generating plasmas by means of dielectric barrier electrical discharges and also to a device for carrying out such a method.

Dielectrically impeded electrical discharges are electrical gas discharges in which a resulting discharge current is limited by a dielectric shielding of at least one electrode to which a voltage causing the discharges is applied. Therefore, dielectric barrier electrical discharges are only maintained with a changing voltage, but not with a DC voltage applied to the electrode.

STATE OF THE ART

From the DE 10 2011 050 631 A1 discloses a device for generating dielectrically impeded electrical discharges with an alternating high-voltage source and with a plurality of elongated metal electrode bodies coupled to the same output of the alternating high-voltage source. The plurality of electrode bodies are individually capacitively coupled to the output of the AC high voltage source by facing a high voltage bus connected to the output with the interposition of a dielectric solid. The several elongated electrode bodies form the tines of a comb that can be used to combat hair lice. The hair lice are killed when they get in the area of the electric discharge filaments emanating from the tips of the stretched electrode bodies.

From the DE 10 2015 108 884 A1 discloses a device for plasma treatment of an object, in particular a strip-shaped object, with an electrode and a counter-electrode made of electrically conductive material and with an alternating high-voltage generator. The purpose of the alternating high voltage generator is to use an alternating high voltage to induce electrical gas discharges between the electrode and the counter-electrode. A dielectric barrier is connected in series with the gas discharge in order to impede the gas discharge dielectrically. The electrode and the counter-electrode are arranged next to one another in a contact casing of a roller which is rotatably mounted for contacting the object to be treated. Specifically, the contact jacket has a cover layer made of dielectric material that covers the electrode and the counter-electrode. Arranged above the electrode and above the counter-electrode is a linear ignition electrode made of electrically conductive material, which is separated from the electrode and the counter-electrode by the cover layer and is exposed on the outer circumference of the contact jacket. The ignition electrodes couple capacitively to the electrode or counter-electrode below them, and field peaks of the electrical field form towards them over the contact jacket. These field peaks ensure reliable ignition of the gas discharges between the areas of the contact jacket defined by the ignition electrodes. Due to the current flowing through the gas discharges, the field peaks on the ignition electrodes balance out so that their presence does not prevent the gas discharges from being evenly distributed over the contact jacket.

From the DE 10 2006 011 312 A1 there is known an apparatus for plasma treatment comprising an electrode in front of which a dielectric shield is arranged and an AC high voltage source for applying an AC high voltage to the electrode. The AC high voltage induces dielectric barrier gas discharges to generate a plasma in a gas at atmospheric pressure located in front of the dielectric shield. The electrode has a two-dimensional extended surface over which the AC high voltage applied to the electrode from the AC high voltage source sustains the plasma across the surface of the electrode. To this end, the surface of the electrode and/or a surface of the dielectric shield has tips facing the gas in front of the dielectric shield. The peaks are provided in an areal distribution. The alternating high voltage applied to the electrode by the alternating high voltage source has a steep voltage rise of at least 5,000 V/µs. The tips of the electrode can be realized by forming the electrode from an electrically conductive powder, for example a bronze powder.

From the DE 10 2013 112 316 A1 a piezoelectric transformer with a surface structure is known which has protruding surface structure segments. The width of each surface structure segment is smaller than the width of the piezoelectric transformer. The surface structure is designed in such a way that a gas discharge caused by the transformer in conjunction with a counter-electrode starts at a large number of discharge initiation points on the surface structure.

From the DE 10 2019 122 930 A1 is a device for generating a gas discharge with a piezoelectric transformer and a known discharge structure. The discharge structure influences the resulting electric field, and in this way the shape of a generated gas discharge or plasma discharge is determined. Depending on the discharge structure used, the known device can be designed to ignite plasma by a dielectric barrier discharge or by a corona discharge. The discharge structure can have an outer metallization and an element made of metal that is, for example, needle-shaped, blade-shaped, wire-shaped or brush-shaped. The above element affects the field distribution of the electric field. If the protruding element is pointed, there will be a strong field increase at the tip of the protruding element. Gas is discharged in a point form at this point. If the protrusion is elongated, gas will be discharged along the entire length of the protrusion. In a brush-shaped protrusion, some of the bristles may be conductive and some of the bristles may be non-conductive. The conductive bristles also cause a field increase at their tips. Non-conductive bristles can be used to mechanically work a surface.

From the DE 21 2018 000 015 U1 is a device for generating a non-thermal atmospheric pressure plasma with a housing in which a piezoelectric transformer is arranged. The housing has a coating to destroy an irritant gas. An opening of the housing is closed by a coupling plate comprising a non-conductive material. The interface plate forms a dielectric barrier whereby plasma can be ignited on the outside of the interface plate. Metallization is arranged on the side of the coupling plate which points away from the piezoelectric transformer. The metallization affects the field generated by the piezoelectric transformer. In this way, the form of plasma ignited on the outside of the coupling plate can be influenced. The plasma can be bundled or fanned out by appropriate shaping or metallization.

OBJECT OF THE INVENTION

The invention is based on the object of demonstrating a method and a device for generating plasmas by means of dielectrically impeded electrical discharges in which pulse energies of the plasma, i. H. Duration and/or current intensities of the discharge currents flowing in individual spatial areas with each rapid increase in the voltage are increased compared to known methods and devices.

SOLUTION

The object of the invention is achieved by a method having the features of independent patent claim 1 and by a device having the features of independent patent claim 10 . Preferred embodiments of the method according to the invention and the device according to the invention are defined in the dependent patent claims.

DESCRIPTION OF THE INVENTION

In a method according to the invention for generating plasmas by means of dielectrically impeded electrical discharges, at least one charge-collecting element made of an electrically conductive material is arranged in and/or on a flat outer surface of a dielectric shielding of an electrode. In this case, the charge collecting element has an electrically conductive collecting area of at least 1 mm ² along the outer surface. At the same time, a virtual rectangle of the smallest area, which encloses the charge accumulation element along the outer edge, has an edge length ratio of its larger edge length to its smaller edge length of no more than 2.5:1. Furthermore, the larger edge length of the virtual rectangle with the smallest area is not greater than 10 mm; the area of the minimum area virtual rectangle is not more than 20% of an electrode area of the electrode extending along the outer surface; and the charge collecting element projects normal to the outer surface by no more than the minor edge length of the outer surface of the electrode dielectric shield. The outer surface of the dielectric shield is placed parallel to an object surface to be treated. In this case, a minimum free distance between the surface or the charge-collecting element and the object surface is at least 0.5 mm and at most 20 mm. If a changing voltage is then applied to the electrode, which is sufficient to cause dielectrically impeded electrical discharges in a working gas between the outer surface and the object surface, a discharge filament emanates from the charge-collecting element with significantly increased pulse energy compared to a charge-collecting element that is not present.

The electrical conductivity of the charge-collecting element on its collecting surface facing the working gas means that the current flowing through the discharge filament is stronger and/or flows longer than without the charge-collecting element. This effect is visually observable when the dielectric barrier electric discharges are caused to a transparent counter-electrode through which the outer surface surface of the dielectric shielding can be observed. A significantly brighter discharge filament then emanates from the charging element, ie a discharge filament with significantly higher pulse energy, the standard of comparison being those discharge filaments which emanate from the dielectric barrier shielding next to the charge collecting element. By this standard of comparison, the increase in pulse energy of the discharge filament by the method of the invention is at least 100%, often at least 300% and often at least 700%.

In this case, a plurality of discharge filaments running parallel to one another can also emanate from the charge-collecting element at the same time. Then each of these discharge filaments typically has an increased pulse energy. At the same time, the number of discharge filaments per unit area emanating from the charge collecting element is significantly smaller than that of such discharge filaments which emanate from the outer surface of the dielectric shielding of the electrode without or also next to the charge collecting element. The sum of the discharge currents flowing over the entirety of the discharge filaments is therefore at most only slightly influenced by the charge collecting element.

The geometric references made to the charge accumulating element mean that the charge accumulating element has a localized shape with low aspect ratio on the outer surface of the dielectric shield, which is essentially spot-shaped. In this case, however, it is not crucial that the charge-collecting element has a specific shape, for example a circular shape. The charge collecting element can also be triangular, square, square, polygonal, star-shaped, #-shaped or generally grid-shaped. Accordingly, it is also not crucial that the charge collecting element has an uninterrupted electrically conductive collecting surface. However, the charge-collecting element is significantly smaller than the electrode area of the electrode arranged on the rear side facing away from the charge-collecting element in the dielectric shielding. These compact dimensions are of approximately the same order of magnitude as the minimum free distance between the outer surface of the dielectric shield or the charge collecting element and the object surface to be treated.

The varying voltage to be applied to create the dielectric barrier electrical discharges in the working gas between the outer surface and the object surface corresponds to what is usual for generating plasmas from dielectric barrier electrical discharges. There should be a steep rise in voltage with each change in voltage, and the voltage changes should follow each other quickly enough to ignite and sustain the plasma as desired.

The electrically conductive collecting surface of the charge collecting element determines the area along the outer surface of the dielectric shielding via which charge carriers can be collected with the aid of the electrical conductivity of the charge collecting element and fed into the discharge filament to increase its pulse energy. From an electrically conductive collecting area of 1 mm ² , a considerable increase in the pulse energy of the discharge filament emanating from the charge collecting element occurs in this way. Preferably, the charge collecting element has a closed electrically conductive collection area of at least 3 mm ² and more preferably at least 6 mm ² along the outer surface of the dielectric shield. The possible pulse energy of the discharge filament increases with increasing collection area. At the same time, however, the probability that more than one discharge filament emanates from the charge-collecting element also increases. A maximum increase in pulse energy is achieved when the collecting surface is not only closed, ie without gaps, but is also particularly compact, ie has a small edge length ratio of preferably no more than 2:1 and even more preferably no more than 1.5:1 . Aspect ratios at 1:1, such as circles and squares, are most preferred.

The larger edge length of the virtual triangle with the smallest area, which encloses the charge-collecting element along the outer surface, is preferably no greater than 8 mm and even more preferably no greater than 6 mm. If this upper limit is observed, the entire charge collected with the charge-collecting element can flow into the discharge filament, so that its pulse energy is increased to the maximum. In the case of larger charge-collecting elements, on the other hand, as already explained, there is a tendency for a plurality of discharge filaments to emanate from the charge-collecting element, which then also have higher pulse energies than without the charge-collecting element.

As a rule, the charge collecting element does not protrude by more than 50% of the smaller edge length of the virtual rectangle normal to the outer surface of the dielectric shielding. Preferably, the charge collecting element is flush with the outer surface of the dielectric shield. This reduces the inclination ed that charge filaments form at the outer edge of the charge-collecting element, which can be at the expense of a central discharge filament with maximum pulse energy.

The minimum free distance between the outer surface of the dielectric shield or the charge collecting element and the object surface is preferably at least 1 mm and at most 10 mm, more preferably at least 2 mm and at most 5 mm. The working gas can have atmospheric pressure. Specifically, the working gas can be an inert gas, air or pure nitrogen.

A distance of the charge collecting element to an edge of the planar outer surface of the dielectric shielding of the electrode is preferably at least 50% of the minimum free distance between the outer surface or the charge collecting element and the object surface. Even more preferably, the distance from the charge collecting element to the edge of the planar outer surface of the dielectric shield is at least as great as this minimum free distance. Stated another way, the charge collecting element is located in a central area of the outer surface of the dielectric shield of the electrode. In this case, the charge collecting element regularly overlaps completely with the electrode surface of the electrode in a projection normal to the outer surface. In other words, the charge-collecting element is entirely present and not also partially adjacent to the electrode.

An electrical conductivity of the electrically conductive material of the charge collecting element is at least 3×10 ² A/Vm along the outer surface. An electrical conductivity of this level is also achieved, for example, by semiconductors or semi-metals. An electrical conductivity of the electrically conductive material along the outer surface of at least 1×10 ⁶ A/Vm is preferred, as is achieved by most metals and is clearly exceeded by noble metals such as copper or silver. The electrical conductivity of the electrically conductive material determines the effectiveness of the collection of charge carriers by the charge collecting element and thus also the maximum area from which charge carriers can be introduced into a discharge filament with the aid of the charge collecting element. In addition, the electrically conductive material is to be selected in such a way that it sufficiently withstands the effects of the increased pulse energy from the discharge filaments emanating from it. For this reason too, the use of a noble metal such as copper or silver or a copper- or silver-based alloy may be preferred.

In the method according to the invention, not only a single but also a plurality of charge collecting elements made of the electrically conductive material can be arranged in and/or on the planar outer surface of the dielectric shielding of the electrode. The distances between the multiple charge collecting elements are at least 75% and preferably at least 150% of the minimum free distance between the outer surface of the dielectric shielding or the charge collecting element and the object surface. Furthermore, the electrically conductive collecting surfaces of the plurality of charge collecting elements together cover no more than 50% of the electrode area of the electrode extending along the outer surface. In other words, no charge collecting elements are arranged over at least 50% of the electrode area.

A device according to the invention for carrying out the method according to the invention has an electrode which is provided with a dielectric shield. At least one charge collecting element made of an electrically conductive material is arranged in and/or on an outer planar surface of the dielectric shield. In this case, the same geometric requirements apply to the charge-collecting element as to the method according to the invention. A voltage source of the inventive apparatus provides a varying voltage for application to the electrode to cause dielectric barrier electrical discharges in a working gas between the outer surface and an object surface to be treated.

Alignment elements of the device can be designed to align the outer surface parallel to the object surface, with a minimum free distance between the outer surface or the charge-collecting element and the object surface of at least 0.5 mm and a maximum of 20 mm, preferably at least 1 mm and a maximum of 10 mm and more more preferably at least 2 mm and at most 5 mm.

Several charge collecting elements made of the electrically conductive material can also be arranged in and/or on the flat outer surface of the dielectric shielding of the electrode, with the distances between the charge collecting elements being at least as large as the smaller edge length of the virtual rectangles and with the charge collecting elements preferably being of the same design and /or are distributed uniformly along the outer surface in one or both main directions of extension of the outer surface.

In concrete terms, the charge-collecting elements can be distributed over the object surface in a two-dimensional array and thus fulfill their function of increasing the pulse energy of discharge filaments distributed over the entire object surface. Typically, the distances between the charge collecting elements relative to the free distance between the outer surface and the dielectric shield or the charge collecting elements and the object surface are at least 0.7 times and preferably at least 1.5 times this free distance. The smaller the distance between the device and the surface of the object to be treated, the closer together the discharge filaments lie, regardless of whether charge-collecting elements are present or not. Accordingly, charge-collecting elements can also be arranged closer together if the distance from the object surface is smaller, without an undesired creeping discharge occurring between adjacent charge-collecting elements.

Each charge collecting element preferably has a maximum thickness normal to the outer surface of the dielectric shield of no more than the minor edge length of the virtual rectangle, preferably no more than 50% the minor edge length, and even more preferably no more than 25% the minor edge length. In other words, the charge collecting elements can be comparatively thin and influence the formation of the electric field between the dielectric shielding and a surface to be treated essentially through their electrical conductivity and less through a reduction in the minimum distance to the object surface or a reduction in the dielectric shielding in front of the electrode .

Advantageous developments of the invention result from the patent claims, the description and the drawings.

The advantages of features and combinations of several features mentioned in the description are merely exemplary and can have an effect alternatively or cumulatively without the advantages necessarily having to be achieved by embodiments according to the invention.

The following applies to the disclosure content - not the scope of protection - of the original application documents and the patent: Further features can be found in the drawings - in particular the illustrated geometries and the relative dimensions of several components to one another as well as their relative arrangement and operative connection. The combination of features of different embodiments of the invention or of features of different patent claims is also possible, deviating from the selected dependencies of the patent claims and is hereby suggested. This also applies to those features that are shown in separate drawings or are mentioned in their description. These features can also be combined with features of different patent claims. Likewise, features listed in the patent claims can be omitted for further embodiments of the invention, but this does not apply to the independent patent claims of the granted patent.

The features mentioned in the patent claims and the description are to be understood with regard to their number in such a way that exactly this number or a larger number than the number mentioned is present without the need for an explicit use of the adverb “at least”. So if, for example, a discharge filament is mentioned, this is to be understood in such a way that exactly one discharge filament, two discharge filaments or more discharge filaments occur. The features listed in the patent claims can be supplemented by further features or can be the only features that the subject matter of the respective patent claim has.

The reference signs contained in the claims do not limit the scope of the subject-matter protected by the claims. They only serve the purpose of making the claims easier to understand.

character list

• 1 zeigt schematisch eine erfindungsgemäße Vorrichtung in einer Seitenansicht beim Behandeln einer Objektoberfläche.
• 2 zeigt ein Detail einer gegenüber 1 abgewandelten Ausführungsform der Vorrichtung.
• 3 zeigt das Detail gemäß 2 einer weiteren gegenüber 1 abgewandelten Ausführungsform der Vorrichtung.
• 4 ist eine Ansicht einer Außenoberfläche einer dielektrischen Abschirmung einer Elektrode der Vorrichtung gemäß 1 mit einem kreisrunden Ladungssammelelement.
• 5 zeigt eine Verteilung von Entladungsfilamenten über die Fläche des Ladungssammelelements gemäß 4.
• 6 zeigt die Außenoberfläche mit dielektrischer Abschirmung einer anderen Ausführungsform der Vorrichtung mit einem dreieckigen Ladungssammelelement.
• 7 zeigt die Verteilung von Entladungsfilamenten über die Fläche des Ladungssammelelements gemäß 6.
• 8 zeigt die Außenoberfläche der dielektrischen Abschirmung einer anderen Ausführungsform der Vorrichtung mit einem quadratischen Ladungssammelelement.
• 9 zeigt eine Verteilung von Entladungsfilamenten über die Fläche des Ladungssammelelements gemäß 8.
• 10 zeigt die Außenoberfläche der dielektrischen Abschirmung einer anderen Ausführungsform der Vorrichtung mit mehreren kreisförmigen Ladungssammelelementen.
• 11 zeigt die Außenoberfläche der dielektrischen Abschirmung einer anderen Ausführungsform der Vorrichtung mit mehreren dreieckigen Ladungssammelelementen; und
• 12 zeigt die Außenoberfläche der dielektrischen Abschirmung einer anderen Ausführungsform der Vorrichtung mit mehreren quadratischen Ladungssammelelementen.

The invention is further explained and described below with reference to preferred exemplary embodiments illustrated in the figures.

• 1 shows schematically a device according to the invention in a side view when treating an object surface.
• 2 shows a detail of an opposite 1 modified embodiment of the device.
• 3 shows the detail according to 2 another opposite 1 modified embodiment of the device.
• 4 12 is a view of an outer surface of a dielectric shield of an electrode of the device according to FIG 1 with a circular charge collecting element.
• 5 FIG. 12 shows a distribution of discharge filaments over the surface of the charge collecting element according to FIG 4 .
• 6 Figure 12 shows the outer surface with dielectric shielding of another embodiment of the device with a triangular charge collecting element.
• 7 FIG. 12 shows the distribution of discharge filaments over the surface of the charge collecting element according to FIG 6 .
• 8th Figure 12 shows the outer surface of the dielectric shield of another embodiment of the device with a square charge collecting element.
• 9 FIG. 12 shows a distribution of discharge filaments over the surface of the charge collecting element according to FIG 8th .
• 10 Figure 12 shows the outer surface of the dielectric shield of another embodiment of the device having multiple circular charge collecting elements.
• 11 Figure 12 shows the outer surface of the dielectric shield of another embodiment of the device having a plurality of triangular charge collecting elements; and
• 12 Fig. 13 shows the outer surface of the dielectric shield of another embodiment of the device with multiple square charge collecting elements.

FIGURE DESCRIPTION

In the 1 The device 1 shown is used to generate plasmas by dielectrically impeded electrical discharges. The device 1 has an electrode 2 which is provided with a dielectric shield 3 made of a dielectric 4 . An outer surface 5 of the dielectric shielding 3 is arranged at a free distance 6 parallel to an object surface 7 of an object 8 to be treated. are in 1 Alignment elements 21 of the device 1 shown only schematically are provided. A voltage source 9 is provided in order to apply a changing voltage, for example an AC voltage or a pulsed DC voltage, to the electrode 2 . In this case, this changing voltage can be provided by the voltage source 9 relative to earth or ground, with the object 8 serving as a capacitive counter-electrode to the electrode 2 . It is shown that the object 8 is connected to the voltage source 9 as a counter-electrode 10 to the electrode 2 . The changing voltage applied between the electrode 2 and the counter-electrode 10 causes the desired dielectric barrier electrical discharges in a working gas 11 located between the outer surface 5 and the object surface 7, for example an inert gas, nitrogen or air. Cold physical plasmas are generated by the gas discharges, in which reactive species form, with which the object surface 7 is treated. The dielectrically impeded electrical discharges 12 appear in the form of discharge filaments 13 which extend between the outer surface 5 and the object surface 7 . In order to increase a pulse energy of individual of these discharge filaments 13 , charge collecting elements 14 are embedded in the outer surface 5 in such a way that they end with the outer surface 5 . The charge collecting elements 14 consist of electrically conductive material 15 and collect charge carriers via an electrically conductive collecting surface 20 extending along the outer surface 5 , which amplify the discharge filament 13 emanating from the respective charge collecting element 14 . In other words, by means of each of the charge collecting elements 15, the discharge current flowing across the respective discharge filament 13 is increased or maintained longer with each increase in the voltage, so that the pulse energy of the discharge filament 13 increases. At a minimum, the collection area 20 of each charge collection element 14 is 1 mm ² ; the collecting surface 20 can but does not have to be closed, ie without gaps. The area spanned by a non-closed electrically conductive collecting surface 20 of the charge collecting element 14 is also comparatively small and amounts to a maximum of 20% of an electrode surface 19 of the electrode 2 extending along the outer surface 5.

2 shows in a section through the dielectric shielding 3 in the area of a charge collecting element 14 that this can partially protrude beyond the outer surface 5. This in 3 line collecting element 14 shown is arranged on the outer surface 5 . However, the projection of the charge collecting element 14 above the outer surface 5 is small.

A virtual rectangle with the smallest area 16, as shown in FIG 4 is located in or on the outer surface 5 for the case of a circular charge collecting element 14 . The rectangle 16 is the virtual rectangle of the smallest area that encloses the charge collecting element 14 along the outer surface 5 . In the case of the circular charge-collecting element 14 according to FIG 4 an edge ratio of edge lengths 17 and 18 of the virtual rectangle 16 is 1:1. In other words, the two edge lengths 17 and 18 are the same here. Depending on the shape of the charge collecting element 14, however, there can also be a larger edge length 17 and a smaller edge length 18. Then the edge length ratio is a maximum of 2.5:1. In any case, the larger edge length is not larger either than 10mm. Furthermore, an area of the virtual rectangle 16 is not larger than 20% of an electrode area 19 of the electrode 2 extending along the outer surface 5, see also 1 . The charge collecting element 14 protrudes normal to the outer surface 5 by no more than the smaller edge length.

5 14 shows a top view of the circular charge collecting element 14 according to FIG 4 that several discharge filaments 13 can emanate from this towards the object surface 7 . Whether only one discharge filament 13 or several discharge filaments form is not only a question of the dimensions of the charge collecting element 14, in particular its electrically conductive collecting surface 20 along the outer surface 5, but also the free distance 16 to the surface 7 to be treated. The larger the collecting surface 20 of the charge-collecting element 14 and the smaller the free distance 6, the greater the tendency for a plurality of discharge filaments 13 to extend parallel to one another from the charge-collecting element 14 to the surface 7 to be treated. Typically, multiple discharge filaments 13 are distributed relatively evenly across the collection surface 20 of the charge collection member 14.

In the embodiment of the device according to the invention with the triangular charge-collecting element 14 according to FIG 6 the edge lengths 17 and 18 of the virtual rectangle 16 can be the same or different. For an equilateral triangle, the edge length would be 18 according to 6 smaller than edge length 17.

7 FIG. 1 shows a possible distribution of several discharge filaments 13 over the collecting surface 20 of the charge collecting element 14 according to FIG 6 .

8th shows a square charge-collecting element 14, which is therefore congruent with the virtual rectangle 16 of the smallest area, with the edge lengths 17 and 18 being the same.

9 FIG. 12 shows a possible distribution of discharge filaments 13 over the collecting surface 20 of the square charge collecting element 14 according to FIG 8th .

10 shows several regularly arranged circular charge-collecting elements 14. If the size of the collecting surfaces 20 and the distances between the landing-collecting elements 14 correspond to the free distance 6 according to FIG 1 are matched, a single discharge filament with maximum pulse energy per increase in the voltage from the voltage source 9 can emanate from each of the charge-collecting elements 14 .

11 shows several triangular charge-collecting elements distributed over the outer surface 5, the outer surface 5 being different here than in FIGS 4 , 6 , 8th and 10 has no circular, but rounded square dimensions.

The outer surface 5 also has such rounded square dimensions 12 on, over which several square charge collecting elements 14 are distributed here.

In concrete terms, the individual charge-collecting elements can be formed from copper foil which is bonded to the dielectric 4 made from alumina ceramics, and it can be embedded in the outer surface 5 .

Reference List

1

contraption

2

electrode

3

dielectric shielding

4

dielectric

5

Outer surface of the dielectric shield 3

6

free distance

7

object surface to be treated

8th

object

9

voltage source

10

counter electrode

11

working gas

12

dielectric discharge

13

discharge filament

14

charge collecting element

15

electrically conductive material

16

virtual rectangle

17

edge length

18

edge length

19

electrode surface

20

quilt

21

alignment element

Claims (15)

Method for generating plasmas by means of dielectrically impeded electrical discharges (12) with - arranging at least one charge collecting element made of an electrically conductive material (15) in and/or on a planar outer surface (5) of a dielectric shield (3) of an electrode (2), - wherein the charge collecting element (14) has an electrically conductive collecting surface (20) of at least 1 mm along the outer surface (5). ² , - wherein a virtual rectangle (16) of the smallest area, which encloses the charge-collecting element (14) along the outer surface (5), has an edge length ratio of its larger edge length (17) to its smaller edge length (18) of no more than 2.5 : 1, - wherein the larger edge length (17) is not greater than 10 mm, - wherein the area of the virtual rectangle (16) of the smallest area is not greater than 20% of an electrode area (19) extending along the outer surface (5) the electrode (2) and - the charge collecting element (14) protruding normal to the outer surface (5) by no more than the smaller edge length (18), - aligning the outer surface (5) parallel to an object surface (7) to be treated, wherein a minimum free distance (6) between the outer surface (5) of the dielectric shield (3) or the charge collecting element (14) and the object surface (7) is at least 0.5 mm and at most 20 mm, and - applying a changing voltage to the electrode (2) in order to cause dielectrically impeded electrical discharges (12) in a working gas between the outer surface (5) and the object surface (7), a discharge filament (13) with increased pulse energy emanating from the charge collecting element (14). procedure after claim 1 , characterized in that the charge collecting element (14) has a closed electrically conductive collecting surface (20) of at least 3 mm ² and preferably of at least 6 mm ² along the outer surface (5). procedure after claim 1 or 2 , characterized in that the aspect ratio is not more than 2: 1 and preferably not more than 1.5: 1. Method according to one of the preceding claims, characterized in that the larger edge length (17) is no greater than 8 mm and preferably no greater than 6 mm. Method according to one of the preceding claims, characterized in that the charge-collecting element (14) protrudes normal to the outer surface (5) by no more than 50% of the smaller edge length (18) and preferably ends flush with the outer surface (5). Method according to one of the preceding claims, characterized in that the minimum free distance (6) between the outer surface (5) or the charge-collecting element (14) and the object surface (7) is at least 1 mm and at most 10 mm, preferably at least 2 mm and at most 5 mm, the working gas being at atmospheric pressure. Method according to one of the preceding claims, characterized in that a distance from the charge collecting element (14) to an edge of the flat outer surface (5) of the dielectric shielding (3) of the electrode (2) is at least 50% and preferably at least 100% of the minimum free distance (6) between the outer surface (5) or the charge-collecting element (14) and the object surface (7), the charge-collecting element (14) in a projection normal to the outer surface (5) being completely in contact with the electrode surface (19) of the electrode (2 ) overlapped. Method according to one of the preceding claims, characterized in that an electrical conductivity of the electrically conductive material (15) along the outer surface (5) is at least 3 × 10 ² A/Vm, preferably at least 1 × 10 ⁶ A/Vm. Method according to one of the preceding claims, characterized in that a plurality of charge-collecting elements (14) made of the electrically conductive material (15) are arranged in and/or on the flat outer surface (5) of the dielectric shielding (3) of the electrode (2), whose Distances among each other are at least 75% and preferably at least 150% of the minimum free distance (6) between the outer surface (5) or the charge collecting element (14) and the object surface (7) and their electrically conductive collecting surfaces (20) together not more than 50% the electrode surface (19) of the electrode (2) extending along the outer surface (5). Device (1) for carrying out the method for generating plasmas by means of dielectrically impeded electrical discharges (12) according to one of the preceding claims, having - an electrode (2) which is provided with a dielectric shielding (3), - at least one charge-collecting element (14 ) made of an electrically conductive material (15), which is arranged in and/or on a planar outer surface (5) of the dielectric shielding (3), - wherein the charge collecting element (14) along the outer surface (5) has an electrically conductive collecting surface (20 ) of at least 1 mm ² , - wherein a virtual rectangle (16) of the smallest area, which encloses the charge-collecting element (14) along the outer surface (5), has an edge length ratio of its larger edge length (17) to its smaller edge length (18) of no more than 2.5: 1, - the larger edge length (17) being no larger than 10 mm, - wherein the area of the virtual rectangle (16) of the smallest area is not larger than 20% of an electrode area (19) of the electrode (2) extending along the outer surface (5) and - wherein the charge collecting element (14) is normal to the outer surface (5) by no more than the smaller edge length (18), and - a voltage source (9) which provides a changing voltage for application to the electrode (2) in order to dielectrically impeded electrical discharges (12) in a working gas between the outer surface (5) and an object surface (7) to be treated. Device (1) after claim 10 , characterized in that alignment elements (21) of the device (1) are designed to align the outer surface (5) parallel to the object surface (7), with a minimum free distance (6) between the outer surface (5) or the charge-collecting element ( 14) and the object surface (7) is at least 0.5 mm and at most 20 mm, preferably at least 1 mm and at most 10 mm and more preferably at least 2 mm and at most 5 mm. Device (1) after claim 10 or 11 , characterized in that a plurality of charge-collecting elements made of the electrically conductive material (15) are arranged in and/or on the flat outer surface (5) of the dielectric shielding (3) of the electrode (2), the distances between the charge-collecting elements (14) being at least are as large as the smaller edge length (18) and the charge collecting elements (14) are preferably distributed equally and/or uniformly along the outer surface (5). Device (1) after claim 12 , characterized in that the charge-collecting elements (14) are distributed in a two-dimensional array over the object surface (7). Device (1) after claim 12 or 13 , as far as related to claim 11 , characterized in that the distances between the charge-collecting elements (14) are at least 75% and preferably at least 150% of the minimum free distance (6) between the outer surface (5) or the charge-collecting elements (14) and the object surface (7). Device (1) according to one of Claims 10 until 14 , characterized in that each charge collecting element (14) has a maximum thickness normal to the outer surface (5) of no more than the minor edge length (18), preferably no more than 50% of the minor edge length (18) and more preferably no more than 25% of the smaller edge length (18).

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