DE102021130776B4 - DEVICE AND METHOD FOR TREATMENT OF LIQUID - Google Patents

Abstract

Device for treating liquid, having an irradiation carrier (1) which can be rotated about an axis of rotation, the rotatable irradiation carrier (1) having the following:an exposure surface (2),at least one electrode (8) with an electrode surface, the electrode surface being in the exposure surface ( 2). can be irradiated in some areas with electrons (6).

Description

The invention relates to a device and a method for treating liquid, in which a liquid to be treated is directed onto an irradiation carrier and irradiated with electrons. The radiation carrier is rotated in the process. The radiation carrier has at least one electrode which can be used to measure how many electrons have hit the radiation carrier.

Electron beam treatment of fabrics is a well-known technique, for example for curing or modifying polymers and for sterilization. The problem is that most industrial processes require high throughput. In liquid processing, the desired throughput can be achieved by treating a thick liquid film with high radiant energy or treating a thin liquid film with low radiant energy. In the case of ionizing radiation, high-energy processing (more than 600 keV) requires massive and heavy shielding, leading to high investment costs, space problems and access to industrial processes. When irradiated with low-energy electron beams (300 keV or less), the size and shielding of the system and the investment are significantly smaller. On the other hand, the penetration depth of the electrons into the matter is lower, e.g. only a few hundred micrometers in water. For a large throughput, therefore, high beam powers with low radiation energy and, at the same time, rapid treatment of thin liquid films are advantageous.

The pamphlet U.S. 4,074,138 A describes a device in which a material to be treated flows from a hopper in a thin layer onto a rotating drum and is moved through an irradiation zone formed by an electron beam directed radially onto the drum. The hopper can use an adjustable metering edge or a rotatable metering roller to vary the thickness of the layer of material on the drum.

The pamphlet US 3891 855 A describes a device for irradiating a liquid material with electrons. For this purpose, a hollow body is arranged in a container for the material and the material flows in the form of a thin layer over a surface of the body while the material is being irradiated.

The pamphlet U.S. 6,486,481 B1 describes an apparatus and method for treating polymeric material such as polytetrafluoroethylene with radiation. The polytetrafluoroethylene is moved at an even and constant depth on an adapted vibrating table under an electron beam. The vibrating table is sealably covered, allowing for a controlled environment.

The pamphlet U.S. 6,143,805 A describes a method of sterilizing a liquid adhesive composition comprising exposing the composition to electron beam radiation while sealed in a container.

It is the object of the present invention to specify a device and a method for treating liquids which enable a high throughput even when using low-energy electron beams.

The object is achieved by the device for treating liquid according to claim 1 and the method for treating liquid according to claim 19. The respective dependent claims specify advantageous developments of the device according to the invention and the method according to the invention.

The invention relates to a liquid treatment device. The treatment can be carried out using electrons that are radiated onto the liquid. The device according to the invention has a radiation carrier that can be rotated about an axis of rotation. The radiation carrier can be a disk, for example, preferably with a circular circumference. It can then be referred to as a radiation disk. The rotatable irradiation carrier has an exposure surface. The exposure surface can be a surface of the radiation carrier. If the radiation carrier is designed as a disk, the exposure surface can be one of those surfaces of the disk that extend parallel to the plane of the disk.

The radiation carrier also has at least one electrode with an electrode surface. In this case, the electrode surface is arranged in the exposure surface and advantageously merges continuously into it. If the electrode surface and the exposure surface are flat, this can mean that these surfaces are in the same plane. If the exposure surface is curved, the electrode surface is advantageously curved in such a way that it continues the exposure surface in the area of the electrode surface. The fact that the electrode surface merges smoothly into the exposure surface can mean that the electrode surface merges into the exposure surface without a step or gap.

The device for treating liquid also has a supply line with which a liquid can be fed onto the radiation carrier. The liquid can preferably be conducted with the feed line to the exposure surface or to a surface of the radiation carrier that is separated from it by an intermediate layer, for example an insulating layer. It should be noted in this regard that the exposure surface does not necessarily have to be an outer surface of the radiation carrier, but can be covered on the outside by one or more layers, which layers can also be counted towards the radiation carrier. In such a case, the liquid can be conducted to the corresponding layer of the radiation carrier, which can cover the exposure surface, with the supply line.

According to the invention, the device for the irradiation of liquid also has an electron irradiation device with which liquid that has been directed onto the irradiation carrier can be irradiated with electrons at least in regions. If the liquid is conducted onto the irradiation carrier via the supply line mentioned, the liquid can be irradiated with electrons at least in regions using the electron irradiation device on the irradiation carrier. That is, the electron irradiation device preferably irradiates electrons toward the exposure surface onto the irradiation substrate. To this end, the electron beam irradiation device can be arranged, for example, above the exposure surface.

In an advantageous embodiment, the device for treating liquid can have an insulating layer which covers the electrode surfaces of the at least one electrode. The insulating layer is preferably arranged on the exposure surface and the electrode surfaces, particularly preferably directly thereon. Advantageously, the surface of the insulating layer facing away from the exposure surface is continuous, ie without sharp-edged elevations or depressions. The layer is preferably uniformly thin and particularly preferably resistant to ionizing radiation, in particular electron beams. The insulating layer can also be advantageous if there is only one electrode, since in this way areas of different surface properties on the irradiation area, which would lead to discontinuities in the liquid film at the transition points, for example due to different surface tensions, can be avoided. If a plurality of the electrodes are provided, the insulating layer can prevent the liquid to be treated from causing an electrical short circuit between the electrodes. The layer can have or consist of parylene, for example, as the material. The insulating layer preferably has a thickness of greater than or equal to 0.1 μm, preferably greater than or equal to 0.6 μm and less than or equal to 50 μm, preferably less than or equal to 10 μm. The thickness of the insulating layer is preferably dimensioned in such a way that a sufficient number of electrons can pass through it in order to be collected in the electrodes and to generate a current flow via a leakage resistance to ground.

In order to insulate these from one another when a plurality of electrodes are present, the radiation carrier can also be electrically insulating itself where the electrodes are arranged. The electrodes can thus be embedded in the exposure surface in an insulating manner.

Preferably, the irradiation carrier has at least two of the electrodes, each having one of the electrode surfaces. This makes it possible, for example, to use one of the electrodes as a reference electrode.

The liquid is preferably conducted with the supply line onto the radiation carrier in a region which is at a distance greater than zero from the axis of rotation. The axis of rotation therefore preferably does not intersect the area in which the liquid is directed onto the radiation carrier by means of the supply line. Since the liquid moves outwards radially to the axis of rotation when the radiation carrier is rotated, this results in an area that remains free of liquid.

In an advantageous embodiment of the invention, one of the electrodes can then be arranged as a reference electrode in an area around the point of intersection of the axis of rotation with the radiation carrier or with the exposure surface, which is closer to this point of intersection than the feed line area. The reference electrode is then not covered by the liquid to be irradiated. The reference electrode is preferably located in a region which is at least temporarily irradiated with electrons during a rotation of the irradiation carrier about the axis of rotation.

In an advantageous embodiment of the invention, the device can have at least one signal amplifier, particularly preferably a signal amplifier for each of the electrodes, which is electrically connected to the corresponding electrode and which is set up to generate a voltage drop across the bleeder resistor via which the current from the corresponding Electrode flows to reinforce. The signal amplifier or signal amplifiers are preferably arranged in a fixed manner on the radiation carrier. In this way, even very small currents in the pA or µA range can be generated as a voltage drop across a bleeder resistor measured and the voltage signal amplified.

The at least one signal amplifier can advantageously be arranged, for example, on the irradiation carrier on a rear side of the irradiation carrier that faces away from the electron irradiation device. As a result, the signal amplifier itself is not irradiated with electrons.

The radiation carrier can advantageously have a pick-up electrode for one, several or all of the signal amplifiers. The device can then also have at least one brush contact. The at least one brush contact and the at least one pick-off electrode can then be arranged relative to one another in such a way that the pick-off electrode touches the brush contact at least temporarily during one revolution of the radiation carrier. In this way, the voltage signals generated by the signal amplifier can be derived from the radiation carrier as measurement signals. Alternatively or additionally, the measurement signals can also be transmitted optically from the radiation carrier to a fixed receiver.

In a preferred embodiment, the respective tapping electrode can touch the corresponding brush contact while at least one of those electrodes is located in an irradiation area of the electron irradiation device, which is electrically connected to the corresponding signal amplifier. The irradiation area is the area into which the electron irradiation device irradiates electrons. This irradiation area is normally fixed and the irradiation carrier rotates under the irradiation area. Advantageously, precisely that pick-up electrode can be connected to the brush contact that is electrically contacted with one of the signal amplifiers, which amplifies the current from an electrode that is in the irradiation area at the time of contact between the brush contact and pick-up electrode, i.e. is being irradiated with electrons.

A suitable signal amplifier is preferably provided for each electrode, which is particularly preferably attached directly in the vicinity of the electrode, but not in the irradiation area. The signal amplifier or amplifiers can advantageously be supplied with power via sliding contacts or be battery-operated.

In an advantageous embodiment of the invention, the electrode surfaces of at least some of the at least one electrode can have the shape of concentric circle segments. The center, to which the circle segments can be concentric, can then be the axis of rotation of the radiation carrier. Areas that extend in the circumferential direction around the axis of rotation in a specific angular range and have a constant expansion in the radial direction can be regarded as segments of a circle. Advantageously, these circular segments can be elongate, that is to say they can extend further in the circumferential direction than in the radial direction.

Preferably, three of the electrode surfaces in the form of concentric circular segments can extend in the circumferential direction around the axis of rotation over the same angular range (ie advantageously be arranged in the same radial direction), but have different radii. A radial distance between two adjacent ones of the three electrode surfaces in each case is particularly preferably the same. However, the circle segments can also be arranged in different radial directions.

In an advantageous embodiment, at least two, particularly preferably three, of the electrode surfaces can have the same radii and particularly preferably be arranged equidistant from one another. These electrode surfaces can thus pass through the irradiation area one after the other. The configuration with three electrode surfaces of the same radius can be combined with the configuration described above with three electrode surfaces each in the form of concentric circular segments. This results in an embodiment in which three electrode surfaces configured as concentric circular segments are present in at least two, preferably three angular regions spaced apart from one another. In the case of three angular ranges, each with three concentric electrode surfaces, there are nine electrode surfaces here.

Advantageously, the one or more electrode surfaces with the smallest radius can each serve as a reference electrode. For this purpose, this smallest radius is preferably arranged closer to the axis of rotation than the feed line with which the liquid can be guided onto the radiation carrier.

The surface of the radiation carrier onto which the liquid can be directed is preferably smooth. This can be the exposure surface with the electrode surfaces arranged therein, or else an insulating layer arranged on the exposure surface. The result of this is that the liquid is not disturbed when the radiation carrier is rotated and thus has a uniform, preferably constant, layer thickness.

In an advantageous embodiment, the device according to the invention can have a collection system with which liquid flowing over an edge of the radiation carrier or the exposure surface can be collected. The collection system preferably surrounds the radiation carrier along its entire circumference. Advantageously, the collection system may comprise a tube or lip with one edge touching the exposure surface. In this way, the collection system can scrape liquid from the liquid-containing surface of the radiation carrier at its edge.

The collection system preferably has a collection channel arranged along an edge of the radiation carrier, in which liquid flowing off the radiation carrier in the radial direction can be collected. Advantageously, the collecting channel can be open towards the radiation carrier or its edge. However, this is not mandatory. Alternatively, the collection channel can also be open at the top, for example. In this case, the liquid draining from the radiation carrier can also go into the collecting trough by gravitational action. If, as described, a tube or a lip is provided, the liquid can also be guided through this into the collection channel if it is not open towards the edge of the radiation carrier.

If the collecting trough is open towards the edge of the radiation carrier, an opening surface of the collecting trough, with which the collecting trough is open towards the edge of the radiation carrier, can be at a non-vanishing angle to a radially running tangent at the edge of the exposure surface. Liquid that flows off the irradiation surface radially can be thrown into this opening surface and thus into the collection channel. The opening surface of the collecting channel can thus be arranged such that it is intersected in the radial direction by a straight extension of the irradiation carrier or the exposure surface.

Advantageously, the collecting trough has a baffle which is intersected in the radial direction by a straight extension of the radiation carrier or the exposure surface or the surface onto which the liquid is directed. Liquid draining from the irradiation surface in the radial direction will then be caught by the baffle and run into a recessed area of the collection trough. For this purpose, the collecting channel can have the depression region, which can be delimited outwards in the radial direction by the baffle and forms a concave channel that can receive the liquid.

Advantageously, the radiation carrier and/or that surface of the radiation carrier to which the liquid can be directed and/or the exposure surface can be convex, concave or flat. Which of the forms is preferred depends on how the thickness distribution of the liquid film is desired and is suitable for the viscosity of the liquid. Preferably, the corresponding surface has a strictly monotonic curvature or, in the planar case, curvature zero everywhere. The corresponding surface can advantageously be circular. The axis of rotation of the rotatable radiation carrier preferably passes through the corresponding surface at its center. The axis of rotation is preferably perpendicular to the corresponding surface at the point of passage.

The invention also relates to a method for treating liquid using an apparatus as described above. In this case, a liquid is directed onto the radiation carrier at a supply line area. In this case, the feed line area is that area into which the liquid is fed through the feed line onto the radiation carrier. The feed line area can preferably be fixed, ie it cannot rotate with the radiation carrier. However, configurations are also conceivable in which the supply line area rotates with the radiation carrier.

The liquid is at least partially irradiated with electrons on the irradiation carrier. The irradiation is carried out by the electron irradiation device.

In the method according to the invention, at least one current is then measured from at least one of the at least one electrode and a property of the liquid is inferred from the measured current. In particular, the dose radiated into the liquid can be inferred from the measured current. For example, at least one voltage drop generated by a current from at least one of the at least one electrodes through the derivation via a bleeder resistor to ground can be measured and a property of the liquid can be inferred from the current calculated from the measured voltage drop. The dose radiated into the liquid can be deduced from the calculated current.

In an advantageous embodiment of the method according to the invention, the irradiation carrier can rotate in such a way that a volume element of the liquid moves from the point at which the liquid is directed onto the exposure support moves to an outer edge of the exposure support or the exposure surface while the exposure support rotates less than 360 degrees. The volume element thus reaches the edge before the radiation carrier has rotated completely around the axis of rotation.

In an alternative method, the rotational speed of the radiation carrier can be selected such that a given volume element of the liquid moves exactly within a full 360 degree revolution to the edge of the radiation carrier or the exposure surface.

In a further optional embodiment, the rotational speed of the radiation carrier can be selected in such a way that each volume element moves within more than one full rotation of the radiation carrier from the feed area to the edge.

The irradiation area, ie that area which can be irradiated with electrons or is irradiated by the electron irradiation device, can optionally include the entire exposure surface. Alternatively, the irradiation area can be congruent with the exposure surface. In a further alternative, the irradiation area can be a portion of the exposure surface that is not the entire exposure surface.

In order to achieve a homogeneous distribution of the dose, it is advantageous if the rotational speed is chosen so that each volume element, as described above, moves from the feed area to the edge in less than one full revolution or exactly one full revolution, if the irradiation area completely covers the exposure surface contains or is congruent with it.

If the irradiation area covers only part of the exposure surface, not the entire exposure surface, it is advantageous if each volume element of the liquid moves within more than one revolution from the supply area to the edge of the exposure surface, so that each volume element has passed through the irradiation area at least once.

Those properties that can be inferred from the measured or calculated current are, for example, an irradiation dose (e.g. energy transferred to the liquid with a density ρ by irradiation with electrons per volume element), an energy release to the liquid, a progress in the treatment of the Liquid, a layer thickness, and/or layer thickness distribution of the liquid.

An energy of the electrons directed onto the radiation carrier is preferably less than or equal to 600 keV, preferably less than or equal to 500 keV, preferably less than or equal to 300 keV, and/or greater than or equal to 80 keV, preferably greater than or equal to 150 keV.

The treatment according to the invention can be, for example, disinfection of the liquid or inactivation of components of the liquid (e.g. viruses). For these treatment examples, the applied energy dose is important (e.g. measured in kGy = kJ/kg). In a first approximation, this can be determined by the number of electrons that have given up their kinetic energy in the volume element of the liquid. With the knowledge of the number of electrons that have entered the volume element per unit of time and the detection of the number of electrons that have left the volume element on the opposite side, it is possible with knowledge of the electron energy and the densities and thicknesses of all those on the electron path Materials, as well as the residence time of the volume element in the irradiation zone, e.g. the energy dose absorbed by the volume element can be estimated.

In the following, the invention is to be explained by way of example with reference to a number of figures. The same reference symbols designate the same or corresponding features. The features described in the examples can also be implemented independently of the specific example and can be combined between the examples.

• 1 eine schematische Darstellung eines Beispiels einer erfindungsgemäßen Vorrichtung zur Behandlung von Flüssigkeit,
• 2 ein weiteres Beispiel einer erfindungsgemäßen Vorrichtung zur Behandlung von Flüssigkeit,
• 3 zeigt eine einfache Messbeschaltung einer Elektrode,
• 4 einen Verlauf einer relativen Dosis in Abhängigkeit von der Eindringtiefe von Elektronen einer Energie von 150 keV in eine beispielhafte Materialanordnung ohne Flüssigkeitsfilm,
• 5 einen Verlauf einer relativen Dosis in Abhängigkeit von der Eindringtiefe von Elektronen einer Energie von 200 keV in eine zu 4 identische Materialanordnung ohne Flüssigkeitsfilm,
• 6 einen Verlauf einer relativen Dosis in Abhängigkeit von der Eindringtiefe von Elektronen einer Energie von 150 keV in eine zu 4 identische Materialanordnung mit zusätzlichem Flüssigkeitsfilm,
• 7 eine schematische Aufsicht auf eine Expositionsoberfläche mit konzentrisch ringförmigen Elektroden,
• 8 eine schematische Darstellung eines Spannungssignals, hervorgerufen durch einen Stromfluss aus einer der Elektroden in 7 über einen Ableitwiderstand gegen Masse,
• 9 ein Beispiel einer Kalibrierungskurve,
• 10 Veränderung des Spannungssignals, hervorgerufen durch einen Stromfluss aus zwei verschiedenen der in 7 gezeigten Elektroden bei halbiertem Strom der Elektronenbestrahlung,
• 11a und 11b Veränderung des Flächeninhalts unter einer Tiefendosiskurve im Bereich einer der Elektroden mit und ohne Flüssigkeitsschicht bei gleicher Elektronenenergie,
• 12 einen Schnitt durch einen Bestrahlungsträger mit auf dem Bestrahlungsträger angeordnetem Dosimeterfolienstapel,
• 13 eine Aufsicht auf eine Expositionsoberfläche mit über einer der Elektroden angeordneten Dosimeterfolien,
• 14 Zeitverlauf der Signale der äußeren der in 7 gezeigten Elektroden,
• 15 Zeitverlauf der Signale von im gleichen Winkelbereich angeordneten Elektroden in 7,
• 16 ein Beispiel eines Bestrahlungsträgers mit konvexer Expositionsoberfläche und einem Sammelsystem für Flüssigkeit,
• 17 ein Beispiel einer ebenen Expositionsoberfläche mit einem alternativen Sammelsystem und
• 18 eine Aufsicht auf eine Expositionsoberfläche mit exzentrisch angeordnetem Zuleitungsbereich sowie einem Sammelsystem mit Abziehlippen.

It shows

• 1 a schematic representation of an example of a device according to the invention for the treatment of liquid,
• 2 a further example of a device according to the invention for the treatment of liquid,
• 3 shows a simple measuring circuit of an electrode,
• 4 a course of a relative dose as a function of the penetration depth of electrons with an energy of 150 keV in an exemplary material arrangement without a liquid film,
• 5 a course of a relative dose as a function of the penetration depth of electrons with an energy of 200 keV in a 4 identical material arrangement without liquid film,
• 6 a course of a relative dose as a function of the penetration depth of electrons with an energy of 150 keV in a 4 identical material arrangement with additional liquid film,
• 7 a schematic plan view of an exposure surface with concentric ring-shaped electrodes,
• 8th a schematic representation of a voltage signal caused by a current flow from one of the electrodes in 7 via a bleeder resistor to ground,
• 9 an example of a calibration curve,
• 10 Change in the voltage signal caused by a current flow from two different ones of the in 7 electrodes shown with half the current of electron irradiation,
• 11a and 11b change in the surface area under a depth dose curve in the area of one of the electrodes with and without a liquid layer at the same electron energy,
• 12 a section through a radiation carrier with a stack of dosimeter foils arranged on the radiation carrier,
• 13 a plan view of an exposure surface with dosimeter foils placed over one of the electrodes,
• 14 Time course of the signals of the outer of the in 7 shown electrodes,
• 15 Time course of the signals from electrodes arranged in the same angular range in 7 ,
• 16 an example of a radiation carrier with a convex exposure surface and a liquid collection system,
• 17 an example of a flat exposure surface with an alternative collection system and
• 18 a top view of an exposure surface with an eccentrically arranged supply area and a collection system with pull-off lips.

1 Fig. 12 shows schematically an apparatus for treating liquid according to the present invention. The device has a radiation carrier 1 which can be rotated about an axis of rotation. The axis of rotation here runs centrally through the radiation carrier 1 and is perpendicular to it. The irradiation carrier 1 has an exposure surface 2 in which at least one electrode, which is not shown in this figure, is arranged. The irradiation device also has a supply line 3 with which a liquid 4 can be fed onto the irradiation carrier 1 . in 1 example shown, the supply line 3 opens at an intersection of the axis of rotation with the exposure surface 2 on the exposure surface 2. The supply line 3 runs through the radiation carrier 1 and opens into an opening in the exposure surface 2. The in 1 The device shown also has an electron irradiation device with an electron beam exit window 5, with which liquid 4 directed onto the irradiation carrier 1 can be irradiated with electrons 6 at least in regions. in 1 In the example shown, the electrons 6 are emitted from a line-shaped emitter within the electron irradiation device, are accelerated in the direction of the electron exit window, exit the electron irradiation device there as a planar stream of electrons and move in the preferred direction to the exposure surface 2, deflected downwards. The irradiation carrier 1 can be coated on its side facing the electron irradiation device 5 with an insulating layer (not shown here), which covers the electrode surfaces of the electrodes.

in 1 example shown, the supply line 3 runs through the radiation carrier 1 from below. An embodiment in which the supply line 3 ends above the exposure surface 2 is also advantageous, so that the liquid 4 can be guided onto the irradiation carrier 1 from above. In this case, the feed line 3 can also open out above the radiation carrier 1 at a distance greater than zero from the axis of rotation, so that the liquid 4 can be directed onto the radiation carrier 1 in a feed line area spaced apart from the axis of rotation.

2 Fig. 12 shows an example of a liquid treatment device according to the invention. in 2 In the example shown, the irradiation carrier 1 has at least one electrode 8 which is embedded in the exposure surface 2 and whose electrode surface lies in the exposure surface 2 and continuously merges into it. Since the exposure surface is 2 in 2 example shown is flat, the electrode surface of the electrode 8 is also flat and lies in the same plane as the exposure surface 2.

in 2 In the example shown, an insulating layer 7 is provided on the exposure surface, covering the electrode surface of all of the electrodes 8 and optionally covering the entire exposure surface 2 in the example shown. In this way, on the one hand, the electrodes 8 are isolated from one another and, on the other hand, it is achieved that the surface onto which the liquid is directed is homogeneous.

Unlike the in 1 example shown is in 2 the liquid is not conducted from below through the irradiation carrier 1 onto the surface of the irradiation carrier, but through a supply line, not shown here, from above.

in 2 example shown, the device has a signal amplifier 9 . A separate signal amplifier 9 can advantageously be provided for each of the electrodes 8 . The signal amplifier 9 is in electrical contact with the electrode 8 via a line 10 . The signal amplifier 9 is attached to a rear side of the irradiation carrier that faces away from the electron irradiation device 5 . As a result, the is not exposed to the electrons 6. The signal amplifier 9 is in contact with one of the tapping electrodes 12a to 12e via a further electrical line 11. The device has a tapping electrode 12a to 12e for each of the signal amplifiers 9 here. So there are five signal amplifiers 9 provided here, but only one of them in the 2 is shown. Each of the signal amplifiers 9 can be contacted with exactly one of the tapping electrodes 12a to 12e.

The device also has five brush contacts 13a, 13b, 13c, 13d, 13e, each of which touches one of the pickup electrodes 12a to 12e.

in 2 In the example shown, the radiation carrier 1 is rotated by a drive 15 via a shaft 14 . Advantageously, the tapping electrodes 12a to 12e can each completely encircle the shaft 14. In this way, the brush contacts 13a to 13e can contact the respective pick-off electrodes 12a to 12e during the entire rotation of the radiation carrier 1 and the shaft 14. The brush contacts 13a to 13e can then be provided with evaluation electronics, for example, which allow one or more properties of the liquid 4 to be determined from the signals picked up by the brush contacts 13a to 13e.

3 shows a simple way of measuring a current flowing out of the electrode 8. To this end, the electrode 8 is connected to ground via a resistor 16 . A voltage measuring device 17 is connected in parallel with the resistor. In this example, each electrode 8 is connected to ground via a bleeder resistor 16 . The current flow of the captured electrons 8 to ground leads to a voltage drop across the resistor 16. The resistor 16 can, for example, be dimensioned in such a way that a voltage drop of max. 10 V (alternatively 5 V or 100 mV, depending on the input limitation of the measuring device) arises (can be estimated from the proportion of beam current that an electrode catches). This voltage can be measured—in the simplest case with a voltmeter 17—or, for continuous monitoring, with a signal amplifier and/or AD converter, for example, converted into a digital signal, recorded and displayed over time. In both cases, the scanning frequency of the measuring device is preferably so high that the steep signal edges when the electrode enters and exits the irradiation area are correctly recorded (observe the scanning theorem).

Knowing the exact resistance value, the current can be calculated using $$\text{I}=\text{U/R}.$$

A direct current measurement is also possible as an alternative, but is more susceptible to interference.

1. i. Stromversorgung für die Messeinrichtung mit Batterie oder Akku direkt am Ort der Messeinrichtung
2. ii. Messsignalweiterleitung über eine optische Sender-Empfänger-Kombination (z.B. Infrarot)

As an alternative to failure-prone sliding contacts for the power supply of the measuring device and signal transmission, there are the following alternatives

1. i. Power supply for the measuring device with battery or rechargeable battery directly at the location of the measuring device
2. ii. Measurement signal forwarding via an optical transmitter-receiver combination (e.g. infrared)

• - Strom des Elektronenemitters
• - Größe der bestrahlten Elektrodenfläche
• - Anfangsenergie der Elektronen 6
• - Dicke der Luftschicht zwischen Elektronenaustrittsfenster der Elektronenbestrahlungseinrichtung und isolierender Schicht 7
• - Dicke und Dichte der isolierenden Schicht 7
• - wenn vorhanden, Dicke und Dichte der Flüssigkeitsschicht 4

is, as in 2 shown, an insulating layer 7 is provided on the exposure surface 2, the electrons 6 reach the surface of the insulating layer 7, are partly reflected and partly scattered and absorbed within the insulating layer 7 (which is already in the overlying air layer). Only a remaining portion reaches the electrode 8 and is measured there as a current. The proportion depends on

• - Current of the electron emitter
• - Size of the irradiated electrode area
• - initial energy of the electrons 6
• - Thickness of the air layer between the electron exit window of the electron irradiation device and the insulating layer 7
• - Thickness and density of the insulating layer 7
• - if present, thickness and density of the liquid layer 4

Accelerated electrons 6 can penetrate matter, with the maximum possible penetration depth depending on their energy and the density of the matter. Due to the interaction with the matter that takes place, the electrons 6 are slowed down and release energy. The energy transferred is called the dose (kGy = kJ/kg) and is related to the mass of the irradiated matter. The 4 until 6 use an example to illustrate that the effectiveness of energy transfer through impact and scattering processes varies depending on the penetration depth.

mit $$S\approx \mathrm{6,67}\ast {10}^{-11}\frac{{\left(U_B+k_1\right)}^{\frac{5}{3}}}{\rho }\ast k_2↵$$

wobei: $$k_1=1\ast V^{-1}↵$$

$$k_2=1\ast \frac{8}{c{m}^2}↵$$

S

maximale Reichweite der Elektronen

UB

Beschleunigungsspannung

ρ

Dichte der zu durchdringenden Medien (für eine normierte Darstellung wird einheitlich von Wasser ausgegangen)

e

Elementarladung

z

Eindringtiefe

D(z)

Energiedosis am Ort der Eindringtiefe

Dmax

Maximalwert der Energiedosis

The depth dose distribution (Olaf Röder’s dissertation, Development of an electron band radiator for the polymerisation of thin plastic layers, Otto von Guericke University Magdeburg, Faculty of Mechanical Engineering, 1998) can be described approximately for the energy range of the electrons 10 keV ≤ e* _UB ≤ 1 MeV with $$\frac{D\left(\mathrm{e.g}\right)}{D_{max}}=1-\frac{9}{4}{\left(\frac{\mathrm{e.g}}{S}-\frac{1}{3}\right)}^2↵$$

with $$S\approx 6.67\ast {10}^{-11}\frac{{\left(u_B+k_1\right)}^{\frac{5}{3}}}{\rho }\ast {\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="DE102021130776B4\_0006.png,DE102021130776B4\_0007.png"\; state="\{\{state\}\}">k</figure-callout>}}_2↵$$

where: $${\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="DE102021130776B4\_0006.png,DE102021130776B4\_0007.png"\; state="\{\{state\}\}">k</figure-callout>}}_1=1\ast V^{-1}↵$$

$${\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="DE102021130776B4\_0006.png,DE102021130776B4\_0007.png"\; state="\{\{state\}\}">k</figure-callout>}}_2=1\ast \frac{\mathrm{<figure-callout\; id="2"\; label="8th\; c\; m"\; filenames="DE102021130776B4\_0006.png,DE102021130776B4\_0007.png"\; state="\{\{state\}\}">8th</figure-callout>}}{c{m}^{}}↵$$

S

maximum range of the electrons

UB

acceleration voltage

ρ

Density of the media to be penetrated (water is assumed for a standardized representation)

e

elemental charge

e.g

penetration depth

D(z)

absorbed dose at the location of the penetration depth

Dmax

Maximum absorbed dose

For the present configuration, however, it also means that the number of electrons 6 reaching the electrode 8 per unit time for a given arrangement depends only on the number, density and thickness of the layers to be penetrated, the electron energy and the electron current from the electron accelerator .

4 shows the relative dose in percent as a function of the penetration depth in g/m ² . Strictly speaking, the data on the abscissa are surface masses. This representation is typically normalized to the density of water. In this case, a penetrated basis weight of 1 g/m ² corresponds to a penetration depth of 1 µm.

In 4 shows the relationship for the case that no liquid is present on the surface of the radiation carrier 1 and the electrons 6 have been accelerated to an energy of 150 keV. In 5 the relationship is shown for the case in which there is also no liquid 4 on the radiation carrier 1 and the energy of the electrons is 200 keV. 6 finally shows the relationship in the event that liquid 4 is present on the radiation carrier 1 and the electrons 6 have an energy of 150 keV.

In the 4 and 5 the layers shown from left to right are first the exit window of the electron accelerator (e.g. 10 µm titanium), on the far left, then to the right of it a 5 cm thick layer of air, a 10 µm thick layer of parylene and to the right of that a 1 millimeter thick electrode, here made of copper. The 6 exhibits the layers of 4 and 5 on and beyond this a liquid layer with a thickness of 100 µm arranged between the air gap and the layer of parylene.

The penetration depth in g/m ² is plotted on the horizontal axis. A mass per unit area of 1 g/m ² at a density of water (1 g/cm ³ ) means a layer thickness and penetration depth of 1 μm.

The curve indicates the value of the relative dose at the corresponding penetration depth. It can be seen that despite the presence of an insulating layer 7, here the parylene layer and despite the presence of the exit window of the electron accelerator and the air gap, a large proportion of the electrons enter the electrode. The electron current entering the electrode is greater, the higher the energy of the electrons 6, as compared to FIG 4 and 5 shows.

6 shows that the liquid film over the insulating layer 7 reduces the dose transferred into the electrode and thus the current of electrons 6. The reduction depends on the thickness of the liquid film. By determining the dose of the electrons 6 entering the electrode 8 with the aid of the leakage current, the thickness of the liquid film 4 can therefore be inferred. Since the in 6 shown relationship can also depend on properties of the liquid 4, it is advantageous if the radiation carrier also has a reference electrode that is not covered with liquid. For this would then be in the 4 and 5 connection shown. By comparing this relationship with that in 6 The thickness of the film of the liquid 4 can then be determined using the measurement shown. For this purpose, the above-described relationship between the thickness of the liquid film and the number of electrons per unit time that reach the electrode can be used.

7 shows an example of the arrangement of electrodes 8aa to 8cc on the radiation carrier 1. 7 12 shows the top view of the exposure surface 2. An insulating layer 7 that may be present is not shown here, since it would cover the electrodes 8aa to 8cc.

in 7 In the example shown, the electrodes 8aa to 8cc are in the form of concentric segments of a circle about a common center point, which is the point at which the axis of rotation passes through the exposure surface 2. The reference numbers 8aa to 8cc can here indicate the electrodes or the electrode surfaces, depending on the context. Since the exposure surface 2 is circular in the example shown, this is precisely the center point of the circle. The electrodes 8aa to 8cc all extend with their longitudinal direction parallel to the periphery of the exposure surface 2.

Each three of the electrode surfaces 8aa, 8ab, 8ac and 8ba, 8bb, 8bc and 8ca, 8cb, 8cc have different radii and each extend in the circumferential direction around the axis of rotation over the same angular range.

In addition, three of the electrode surfaces 8aa, 8ba, 8ca and 8ab, 8bb, 8cb and 8ac, 8bc, 8cc each have the same radius. Those electrodes in the same angular range have in the in 7 the same distance from one another in the radial direction in the example shown, and such adjacent electrode surfaces with the same radius have the same distance from one another in the circumferential direction in the example shown.

7 FIG. 12 also shows an irradiation area 18, which is the area into which electrons 6 coming from the electron exit window 5 are irradiated. The irradiation area 18 partially covers the exposure surface 2 and also has an area where the exposure surface 2 does not exist, but this is not required. The irradiation area 18 extends in a direction radial to the axis of rotation over such an area that it covers all radii of electrode surfaces 8aa to 8cc. In this way, all electrode surfaces 8aa to 8cc pass the irradiation area 18 in one revolution.

in 7 In the example shown, the supply line 3 (not shown) opens out onto the radiation carrier 1 at a distance from the axis of rotation. The radius of this area 19, which is equal to the distance between the feed line 3 and the axis of rotation, is chosen so large that the innermost electrodes 8ac, 8bc, and 8cc lie within the area 19, i.e. radially closer to the axis of rotation than the feed line 3 As a result, the electrode surfaces 8ac, 8bc and 8cc are not covered by liquid and can be used as reference electrodes. In particular, within one of the angular ranges, this inner electrode surface 8ac, 8bc, 8cc can be used as a reference electrode for measuring the respective outer two electrode surfaces of the corresponding angular range.

In the 7 The configuration shown allows various measurement options.

8th shows the idealized signal supplied by the electrode 8aa, ie the current flowing out of this electrode 8aa or the amplified signal of the voltage drop across the bleeder resistance of the current flowing out of this electrode. The frequency of this signal allows conclusions to be drawn about the rotational speed of the surface.

The level of this signal (without liquid film 4) shows an (idealized) linear dependence on the beam current of the electron source of the electron irradiation device, i.e. the number of electrons per time, and depends on the simultaneously irradiated electrode area and the uniformity of the electron current density within the irradiation area. Therefore, with the same beam current, the signals from the innermost electrodes 8ac, 8bc, 8cc are always smaller than the signals from the outer electrodes 8aa, 8ba, 8ca, 8ab, 8bb, 8cb, if the electrode area of the electrodes 8ac, 8bc, 8cc that can be irradiated at the same time is always smaller than the electrodes 8aa, 8ba, 8ca, 8ab, 8bb, 8cb. In reality, the dependency can deviate somewhat from the linear behavior since electron sources can have different internal leakage currents with different beam currents and the distribution of the electron current density in the irradiation region 18 can also be inhomogeneous. However, the exact dependency can be determined by calibration measurements at different beam currents. For this shows 9 an example of a calibration curve, where the beam current, i.e. the total number of electrons delivered by the electron irradiation device per time, is plotted on the horizontal axis and the signal, i.e. for example the current or measured voltage drop of the leakage current of an electrode via a leakage resistor to ground, is plotted on the vertical axis .

10 shows an example of the signals as a function of time in an arrangement according to 7 are picked up by the electrodes 8aa and 8ac at different beam currents. The one in the 10 shown reference numerals identify the electrode in 7 , which gives the corresponding curve. The solid ones Lines are determined at a beam current of one in arbitrary units and the dotted lines at half this beam current.

After the above calibration, the signal from the liquid-covered electrodes provides a reference to the thickness of the liquid film. With liquid coverage, the signal from the electrode decreases in relation to the areas under the calculated dose curve with and without liquid coverage. The integral under the depth dose curve can be fitted with the measured signal heights in order to determine the position of the electrode surface in the depth dose diagram. This estimate then results in an additional mass per unit area between the electron gun and the electrode, from which a layer thickness can be calculated if the density of the liquid is known. Since the depth dose curve represents a theoretical progression, calibration of the electrode signals with a known layer thickness (e.g. measurement by laser interference) is also recommended here if the exact value of the layer thickness is to be determined. This is usually not necessary for process monitoring, as only layer thickness fluctuations are to be detected without knowing the exact absolute value.

this is in 11a and 11b shown as an example. 11a shows the in 4 curve shown, with the area under the depth dose curve in the region of the electrode being hatched. 11b shows the in 6 depth dose shown, also with shaded area under the depth dose curve in the area of the electrode. In 11a is, as in 4 , no liquid present on the electrode surface, in 11b there is liquid on the electrode surface.

12 shows a section through the radiation carrier 1 in the area of the electrode 8, for example as in FIG 2 . In this case, however, the electrode 8ba is also an electrode calibrated as described above with a stack 20 of film dosimeter foils with a total thickness that corresponds to the liquid film thickness to be simulated. The specific depth dose distribution for the irradiation arrangement and the dependency between layer thickness and electrode signal can thus be determined experimentally.

For this shows 13 an arrangement like that in 7 shown, wherein the entire electrode surface 8ba is covered with the stack of film dosimeter foils 20. The rotating exposure surface 2 is exposed to the electron beam (one or more passes through the exposure area 18).

During the irradiation, the electrode signal can be determined with the selected additional basis weight (density of the dosimeter foil 20, thickness of each foil 20 in the example RIS∅ B3 18 μm). A calibration curve for the respective electrode geometry and position can be created with several stacks 20 of different thicknesses, e.g. with different arrangements one after the other or also on the electrodes 8aa and 8ca. The entire irradiation area 2 and thus all the electrodes can also be covered at the same time. The RIS0 evaluation unit permits a spatially resolved dosimetry of the dosimeter foils 20 and thus also an evaluation at the respective locations of the electrodes. After the irradiation, the applied dose Dµ (according to an international convention, the dosimeter calibration is carried out, advantageously for electron energies <300 keV, in such a way that the indication of the dose applies to the uppermost micrometer of the film) for each individual dosimeter film 20 for the selected number of irradiation runs be determined with a suitable calibrated measuring system. With this, a calibration curve for the depth dose distribution per irradiation run with measuring point distances of e.g. 18 µm in the area of the liquid to be treated can be created and compared with the theoretically calculated curve.

14 12 shows the signals provided by the electrodes 8aa, 8ba and 8ca as a function of time. This time dependence also provides information about the uniformity of the liquid layer thickness over the circumference. Different layer thicknesses would lead to different heights of the signals 8aa, 8ba, 8ca (again, the reference numbers indicate those of the electrodes in 13 . Again, the reference numbers are those of the electrode whose signal is shown.

15 shows the signals of the electrodes 8aa, 8ab and 8ac as a function of time. This measurement also provides information about the radial layer thickness distribution of the liquid. Preferably, the electrode signals are calibrated as described above. The reference electrode 8ac (without liquid coverage) allows one to monitor whether signal fluctuations are caused by beam current fluctuations of the electron source 5, in which case the signals from all three electrodes would fluctuate uniformly, or by layer thickness fluctuations, where the signal from the electrode 8ac would remain stable and only the signals from the Electrodes 8ab and 8aa would fluctuate.

16 shows an example of a section of a device according to the invention for the treatment of liquid, here only the shaft 14 for rotation and the radiation carrier 1 with the exposure surface 2. The in 16 The configuration shown also has a collecting channel 21 which leads to the edge of the radiation carrier 1 is open, the opening surface of the collecting trough 21 with which the collecting trough 21 is open towards the edge of the irradiation carrier 1 being intersected by a straight extension of the irradiation carrier 1 or its exposure surface 2 in the radial direction. Liquid 4 that overflows the edge of the radiation carrier 1 is caught by the channel 21 . The channel 21 can have an outlet 22 with which the liquid 4 can be drained from the channel 21 .

in 16 shown example, the exposure surface 2 is convex, it is therefore in the region of the axis of rotation of the electron beam device 5 closest and away from the electron beam device 5 towards the edge. In the example shown, its course follows a circle segment in section.

17 Figure 12 shows another example of a collection system 21. In this example the exposure surface 2 is flat. The collection channel 21 has a baffle 23 here, which is cut through a straight extension of the radiation carrier 1 and/or the exposure surface 2 .

The collection system here has a cross-section in a plane in which the axis of rotation runs, in which the collection channel 21 has a U-shape, at the radially inner end of which there is a collar which is inclined upwards from the leg of the U in the direction of the irradiation area, whose radially inner edge is closer to the axis of rotation than the edge of the exposure surface. In this way, liquid dripping vertically downward from the edge of the exposure surface 2 is caught by the collar and flows into the chute 21 by gravity. The radially outer edge of the U-shape of the collection chute 21 is elongated and extends from the inner leg to a height above the exposure surface 2 in the direction parallel to the axis of rotation. The extended edge forms the baffle 23 here. In this way, drops of liquid that hit the baffle 23 at the level of the exposure surface 2 would also be caught by the baffle. At the opposite end of the collection channel 21, the impact wall 23 is followed by an annular surface which is horizontal here, ie parallel to the plane in which the exposure surface extends. This annular surface can extend radially inwards to the outer edge of the exposure surface 2 and thus prevents liquid from being able to splash upwards at the edge of the exposure surface 2 . Liquid taken up by the collecting channel 21 can be drained off again through a drain 22 .

The in the 16 and 17 collection systems shown are advantageous for various applications. If the speed of the radiation carrier 1 is so low that the centrifugal forces are not sufficient to move the liquid film radially outwards, then the 16 convex-shaped exposure surface 2 shown cause liquid movement towards the edge by gravity.

If the speed is in a range in which the centrifugal forces ensure a radial movement component of the liquid film, but the liquid drips down due to droplet formation at the edge but essentially due to gravity, the in 16 gutter 21 shown can also be used in conjunction with the planar exposure surface shown in connection .

If the speed is so high that the liquid breaks off tangentially as a drop or film at the edge, the in 17 shown embodiment of the collection system advantageous.

As well in 16 as well as in 17 the collection channel 21 can advantageously be inclined and the outlet 22 can be arranged at the lowest point. In this way, under the influence of gravity, the liquid flows to the outlet 22 and (for example a pipe or hose) and can be fed via this to a collection vessel.

18 shows a top view of an exposure surface 2 as can be used in the invention. Two scrapers 24a, 24b are provided here, for example made of a flexible material with a sealing lip, which interrupts the liquid film 4 on the exposure surface 2. The sealing lips 24a and 24b enclose an obtuse angle with the outer edge of the exposure surface 2 at the location of the corresponding sealing lip 24a, 24b, as a result of which liquid striking the sealing lip 24a, 24b is deflected outwards towards the collection channel 21.

in 18 example shown, the supply line 3 opens from above at a non-negligible distance from the axis of rotation onto the radiation carrier 1.

Claims (24)

Device for treating liquid, having an irradiation carrier (1) which can be rotated about an axis of rotation, the rotatable irradiation carrier (1) having the following: an exposure surface (2), at least one electrode (8) with an electrode surface, the electrode surface being in the exposure surface ( 2) is arranged, wherein the device also has a supply line (3) with which a liquid (4). the radiation carrier (1) can be guided, and an electron irradiation device (5) with which the liquid (4) directed onto the radiation carrier (1) can be irradiated with electrons (6) at least in regions. Device according to the preceding claim, further comprising an insulating layer (7) covering the electrode surfaces of all the at least one electrodes (8). Device according to the preceding claim, wherein the insulating layer (7) has a thickness of greater than or equal to 0.1 µm, preferably greater than or equal to 0.6 µm and/or less than or equal to 50 µm, preferably less than or equal to 10 µm and/or or wherein the insulating layer (7) has such a thickness that together with an exit window of the electron beam device (5), an air gap between the exit window and the liquid (4) and the liquid (4) it has an absorption of less than or equal to 3/ 4 of the energy of the electrons (6). Device according to one of the preceding claims, wherein the electrode surfaces of the at least one electrode (8) merge continuously into the exposure surface (2). Device according to one of the preceding claims, in which the radiation carrier (1) has at least two of the electrodes (8), each with an electrode surface. Device according to one of the preceding claims, wherein with the supply line (3) the liquid (4) can be conducted onto the radiation carrier (1) in a supply line region which is at a distance greater than zero from an intersection of the axis of rotation with the radiation carrier (1). Device according to the preceding claim, further comprising a reference electrode which is arranged in an area around the point of intersection of the axis of rotation with the radiation carrier (1) which is closer to this point of intersection than the feed line area. Device according to one of the preceding claims, further comprising at least one signal amplifier (9), preferably a signal amplifier (9) for each of the electrodes, which is electrically connected to the corresponding electrode and is arranged to amplify a voltage which occurs when a voltage is derived from the corresponding electrode current flowing through a bleeder resistor at the bleeder resistor drops. Device according to the preceding claim, wherein the at least one signal amplifier (9) is attached to the irradiation carrier (1) on a rear side of the irradiation carrier (1) facing away from the electron irradiation device (5). Device according to one of the two preceding claims, wherein the radiation carrier (1) has a pick-off electrode for one, several or all of the signal amplifiers (9), the device also having at least one brush contact, wherein the brush contact and the at least one pick-off electrode are arranged relative to one another in such a way that the pick-off electrode touches the brush contact during one revolution of the irradiation carrier (1), preferably while at least one of those electrodes (8) is in an irradiation area of the electron irradiation device (5) which is is electrically connected to the corresponding signal amplifier (9), the irradiation area being an area which can be irradiated with electrons (6) by the electron irradiation device (5). Device according to any one of the preceding claims, wherein the electrode surfaces of at least some of the at least one electrode (8) are in the form of concentric segments of a circle. Device according to the preceding claim, wherein at least two, preferably three of the electrode surfaces in the form of concentric circular segments have different radii and extend in the circumferential direction around the axis of rotation over the same angular range. Device according to one of the two preceding claims, wherein at least two, preferably three, of the electrode surfaces with the shape of concentric circular segments have the same radii and are particularly preferably arranged equidistantly from one another. Device according to one of the preceding claims, wherein that surface of the radiation carrier (1) onto which the liquid (4) can be directed is smooth. Device according to one of the preceding claims, having a collection system with which liquid (4) flowing over an edge of the irradiation carrier (1) can be collected, the collection system preferably having a hose or a lip which touches the exposure surface (2) with one edge . Device according to the preceding claim, wherein the collection system along a an edge of the radiation carrier (1) and which is open towards the edge of the radiation carrier (1), an opening surface of the collecting channel with which the collection channel is open towards the edge of the radiation carrier (1) being at a non-vanishing angle lies on a surface which is straight in the radial direction and which is tangential to the radiation carrier (1) at its edge. Apparatus according to the preceding claim, wherein the collecting trough has a baffle which is intersected by a straight extension of the irradiation carrier (1), the collecting trough also having a recessed area bounded radially outwards by the baffle and a downwardly concave gutter forms. Device according to one of the preceding claims, in which the radiation carrier (1) and/or that surface of the radiation carrier (1) onto which the liquid (4) can be guided is convex, concave or flat. A method of treating liquid, wherein in an apparatus according to any one of the preceding claims a liquid (4) is directed onto the radiation carrier (1) at a feed line area, the liquid (4) on the radiation carrier (1) is irradiated with electrons (6) at least in certain areas, at least one current is measured from at least one of the at least one electrode (8) and a property of the liquid (4) is deduced from the measured current. Method according to the preceding claim, wherein the radiation carrier (1) rotates in such a way that a volume element of the liquid (4) moves from the point at which it is directed onto the radiation carrier (1) to an outer edge of the radiation carrier (1). moves while the irradiation carrier (1) rotates by less than or equal to 360°. Procedure according to one of claims 19 or 20 , wherein the entire surface, preferably simultaneously, is irradiated with electrons (6). Procedure according to one of claims 19 until 21 , wherein the property of the liquid (4) is an irradiation dose, an energy output to the liquid (4), a progress of the treatment of the liquid (4), a layer thickness of the liquid (4) and/or a layer thickness distribution of the liquid (4). Procedure according to one of claims 19 until 22 , wherein the electrons (6) are irradiated with an energy of less than or equal to 600 keV, preferably less than or equal to 500 keV, preferably less than or equal to 300 keV and/or greater than or equal to 80 keV, preferably greater than or equal to 150 keV. Procedure according to one of claims 19 until 23 , The method using a device according to one of Claims 1 until 18 is performed.

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