DEVICE FOR EXPOSING BULK MATERIAL TO ACCELERATED ELECTRONS

Description

1 / 28 “DEVICE FOR EXPOSING BULK MATERIAL TO ACCELERATED ELECTRONS”

[001] The invention relates to an apparatus for generating accelerated electrons and exposing bulk material to accelerated electrons.

[002] Electron beam technology has been used on an industrial scale for several decades for chemical modification, as well as for disinfection and sterilization of a wide variety of materials and products. This treatment can be carried out economically at atmospheric pressure if the electrons are first released in a vacuum, then accelerated and finally coupled to the treatment area through a beam exit window, usually a thin metal foil. In order to penetrate robust electron exit windows suitable for large-scale use and ensure sufficient treatment depth in the product, acceleration voltages > 80 kV are typically required.

[003] Several methods and beam sources for surface treatment of flat products, such as plates and strips, are well established, while the treatment of molded bodies, bulk materials and fluids on all sides still presents problems. Thus, the uniform incidence of electrons on curved surfaces on all sides is geometrically problematic due to obscuring effects, variable energy absorption of electrons along the gas path and dose heterogeneities due to different projection ratios.

[004] With existing source systems, such as, for example, axial emitters with a fast deflection unit or ribbon emitters (DE 196 38 925 C2) with an elongated cathode, both usually operated with a heated thermionic cathode, treatment of the product on all sides is only possible in a complex way, using additional equipment or at a high cost in terms of equipment and / or technology and / or time.

[005] For example, document DE 10 2006 012 666 A1 describes a Petition 870250091419, dated 07 / 10 / 2025, page 14 / 53 2 / 28 solution that includes axial emitters with associated deflection control and three associated electron exit windows. The three electron exit windows are arranged to completely enclose a triangular free space. If a substrate is guided through this free space, it can be exposed to accelerated electrons across its entire cross-section in a single treatment pass. However, if the substrate does not have the same triangular cross-section as the free space enclosed by the three electron exit windows, the dose distribution of the accelerated electrons on the substrate surface will be heterogeneous. The investment required in equipment for this configuration is also very high, making this solution very expensive.

[006] An apparatus is known from document DE 4434 767 C1 in which a flow of bulk material passes between two surface beam generators and can be exposed to accelerated electrons from both sides. Document EP 0513 135 B1 describes this bilateral treatment of the free-falling bulk material flow using two mirror-inverted axial beam sources with a scanner. What both solutions have in common is the need to use two electron beam sources along with all their power and control components, which still involves a high level of investment in equipment.

[007] Document DE 199 42 142 A1 discloses an apparatus in which bulk material is guided by a surface beam generator in multiple free-fall cycles and exposed to accelerated electrons. Due to the plurality of passes, combined with the intermediate mixing of the bulk material, the probability that the bulk material particles will be exposed to accelerated electrons from all sides is very high in this embodiment. However, the plurality of passes requires a considerable amount of time to carry out the treatment process.

[008] An annular device for generating accelerated electrons is disclosed in document DE 10 2013 111 650 B3, in which all the essential components, Petition 870250091419, dated 07 / 10 / 2025, p. 15 / 53 3 / 28 such as, for example, cathode, anode and electron exit window, are annular, so that, by means of such an apparatus, an annular electron beam can be formed in which accelerated electrons move towards the interior of the ring. By means of such an apparatus, for example, tape-shaped substrates, which are moved through the opening of the apparatus ring, can be exposed to electrons accelerated from the outside over the entire cross-section of the substrate (DE 10 2017 104 509 A1). The treatment of gaseous media (DE 10 2019 134 558 B3) and bulk materials (DE 10 2013 113 688 B3) having only one of these annular sources has already been described. The disadvantage in this document is that such devices are large in terms of configuration due to the external cathodes, insulators, and vacuum vessels, and the electronic processing of substrates can only be carried out in the relatively small volume inside the ring.

[009] Document DE 10 2018 111 782 A1 also describes apparatus with which a ring of accelerated electrons can be generated, but in this case the movement of the electrons is oriented radially outwards. A more favorable relationship between the size of the electron source and the volume of the treatment area is achieved with this arrangement, which is inverted in relation to the direction of electron propagation compared to document DE 10 2013 111 650 B3.

[010] This is even more true because the cold cathodes described in document DE 10 2018 111 782 A1 emit electrons only as a result of stimulation with high-energy ions, which must be provided by an integrated plasma source, which always requires greater effort and more installation space, especially at the very low pressures required for a plasma source to maintain vacuum isolation capability against gas breakdowns at the technologically required acceleration voltage.

[011] Furthermore, this annular source also suffers from the same weakness as all treatment arrangements equipped with only one electron source, namely, the tendency for the energy dose to be deposited unevenly on the various Petition 870250091419, dated 07 / 10 / 2025, page 16 / 53 4 / 28 areas of the surface of the material to be treated (facing or away from the electron exit window). This should be mitigated by means of multiple (time-consuming) passes or by installing electron reflectors on the back side of the material to be treated, facing away from the electron exit window, as described above (whose dose contribution is, however, several times smaller than that applied by the electrons of the primary beam on the front side). Both methods can only alleviate the problem of insufficient dose homogeneity and resolve it satisfactorily.

[012] An effective method for equalizing the surface dose is to add a rotational movement of the bulk material particles, as described in the prior art, such as, for example, in DE 10 2012 209 434 A1. However, this can only be effective if the exposure period of the bulk material particles to the electrons is sufficiently long (adjusted for the rotation period of the bulk material particles). This, in turn, means that, in the usual treatment, and therefore the only economical treatment, of free-falling bulk material, the vertical extent of the electron exit window must be sufficiently large and its aperture area must not be interrupted in that (falling) direction.

[013] Treatment technologies with high dose requirements, such as sterilization tasks, pollutant degradation, and polymer crosslinking, impose an additional requirement for the vertical extent of the opening area of ​​an electron exit window. This results from the fact that the accelerated electrons within the beam source transfer some of their energy to the metal foil and the support grid as they pass through the electron exit window, causing them to heat up. Electron exit windows are therefore usually cooled, but to avoid thermal damage, the electron current density still needs to be limited. Similarly, when the acceleration voltage is defined by the technology, this corresponds to a limited surface dose rate of the electron beam source. A Petition 870250091419, dated 07 / 10 / 2025, page 17 / 53 5 / 28 An increase in the dose transferred to the material being treated is therefore only possible by using a longer exposure time to the electrons, i.e., an extension of the opening area of ​​the electron exit window in the direction of the falling particles of the bulk material.

[014] Both requirements cannot be met with the apparatus described in DE 10 2018 111 782 A1, as they conflict with the horizontal arrangement of the cooling channels above and below the opening area of ​​the electron outlet window, which is implicitly assumed in the cross-sectional drawings. It is known that the distance between these cold surfaces, for which the absorbed portion of the electron energy must be dissipated by heat conduction through the support grid, should not be chosen too large (being limited to only about 7 to 10 cm in configurations designed in practice), since the temperature increase of the metal sheet and the support grid increases linearly with the heat flux density and quadratically with respect to the distance to the heat sink (i.e., the actively cooled edge of the opening area).The limitation resulting from the vertical extent of the uninterrupted opening area not only limits the uniformity that can be achieved, but also the dose that can be achieved in the material being treated in a single pass.

[015] Particularly in the handling of bulk materials, the protection of metal foils against the particles of the bulk material itself, but also against foreign bodies, abrasion and dust that are frequently encountered, is of great importance. Larger particles can cause direct mechanical damage to the foil; dust accumulation would impair electron transmission (and therefore reduce the dose transferred to the product) and increase the locally absorbed portion of electron energy (thus causing localized thermal damage to the metal foil and consequently vacuum leaks). Therefore, it is obvious that process-related components are critical for protecting the electron exit window; Petition 870250091419, dated 07 / 10 / 2025, page 18 / 53 6 / 28 However, document DE 10 2018 111 782 A1 does not contain any technical instructions in this regard.

[016] US patent 2008 / 0267354 A1 also describes annular apparatus with which a high dose of X-rays and also electron beams can be generated. Due to the generation of a high dose of X-rays, such apparatus are unsuitable for the electronic processing of sensitive products, such as seeds, or products that enter the food chain of humans or animals.

[017] The invention is therefore based on the technical problem of creating an apparatus for generating accelerated electrons, in such a way that the disadvantages of the previous technique can be overcome. In particular, it is intended to create an apparatus with a compact configuration, with which, for example, bulk material, but also hollow bodies, can be uniformly subjected, from the inside out, to accelerated electrons on all sides in just one pass, thus achieving high dose values ​​in the product and a long continuous operating time.

[018] The solution to the technical problem is achieved by means of a material having the characteristics of claim 1. Other advantageous embodiments of the invention result from the dependent claims.

[019] An apparatus according to the invention, for exposing bulk material to accelerated electrons, includes a cylindrical electron outlet window as a component of a cylindrical housing enclosing an evacuable space; at least one cathode in wire, ribbon, bar, annular or cylindrical form, which is arranged within the evacuable space and enclosed by the cylindrical electron outlet window, where electrons can be emitted from the wire, ribbon, bar, annular or cylindrical cathode and accelerated radially away from the cylindrical axis of the cylindrical electron outlet window towards the cylindrical electron outlet window. In a preferred embodiment, the wire, ribbon, bar, Petition 870250091419, dated 07 / 10 / 2025, page 19 / 53 A 7 / 28 cylindrical or annular electron source is designed as a thermal emitter or as a hot cathode. Such electron sources require significantly less space than cold plasma-stimulated cathodes. Heating them to the emission temperature can be achieved directly using current passing through the cathode itself or indirectly (by means of thermal radiation or electron impact) using a heating conductor placed inside the cathode and separated from its electrical potential.

[020] An apparatus according to the invention further includes a cylindrical protective grid that encloses the cylindrical electron output window and defines a first annular free space between the cylindrical electron output window and the cylindrical protective grid; an electron reflector that, in turn, encloses the cylindrical protective grid and thus defines a second annular free space between the cylindrical protective grid and the electron reflector; and a series of gas tubes that extend within the first annular free space parallel to the axis of the cylinder of the cylindrical electron output window. All gas tubes are spaced by an identical first dimension from the axis of the cylinder of the cylindrical electron output window and by an identical second dimension from an adjacent gas tube. The gas tubes may be designed, for example, with a round cross-section or, preferably, a rectangular cross-section.Furthermore, each gas pipe has, in two opposite wall regions, at least one opening through which a first gas can be introduced into the first annular free space. In one embodiment, several holes are formed in the two opposite wall regions and arranged along the longitudinal extent of the gas pipes. The holes in the walls of the gas pipes extend through at least one region of the length of the gas pipe opposite the electron exit window. In another embodiment, a slit is formed in the wall of the gas pipes in each of the opposite wall regions and extends along the longitudinal extent of the pipes. Petition 870250091419, dated 07 / 10 / 2025, p. 20 / 53 8 / 28 of gas at least up to the height of the electron exit window.

[021] In an apparatus according to the invention, the bulk material to be exposed to accelerated electrons is passed through the second annular free space between the electron reflector and the cylindrical protective grid. The bulk material is also then exposed to accelerated electrons within this second annular free space; therefore, the second annular free space is also called the treatment area. Electrons are initially emitted from the centrally arranged bar, annular, or cylindrical cathode. The cathode can be designed, for example, as a hot cathode or as a discharge-stimulated cold cathode. In a preferred embodiment, an electric current flows through the bar, annular, or cylindrical cathode, which is thereby heated, thus constituting a thermal emitter or hot cathode.For this purpose, the bar, annular, or cylindrical cathode is electrically connected in a conductive manner to the negative pole of a primary power supply device. The positive terminal of the primary power supply is electrically connected to the cylindrical electron output window, so that the cylindrical electron output window has an anodic electrical potential. In one embodiment, the electron output window has a ground electrical potential. Due to the anodic potential applied to the cylindrical electron output window, the electrons emitted by the bar, annular, or cylindrical cathode are radially accelerated outwards, towards the cylindrical electron output window. After exiting the cylindrical electron output window, the accelerated electrons traverse the first annular free space, pass through the cylindrical protective grid, and, in the second annular free space, strike the material to be exposed to the accelerated electrons.

[022] At least the inner side of the electron reflector, which defines the second annular free space towards the outside, consists of an electron-reflecting material, at least in the region opposite the electron exit window. In this way, the Petition 870250091419, dated 07 / 10 / 2025, page 21 / 53 9 / 28 Electrons that strike the interior of the electron reflector can be reflected by the electron reflector and contribute to the exposure of the bulk material to accelerated electrons. The mentioned region of the electron reflector can be entirely made of an electron-reflecting material, or the electron reflector can be coated, only on the inner part of the mentioned region, with an electron-reflecting material. An example of a suitable electron-reflecting material is a temperature-resistant metal with a high atomic number, such as tungsten or a tungsten alloy. It is advantageous that at least the electron-reflecting region of the electron reflector be cooled so that it does not heat the air in the treatment area. This cooling can be implemented as water cooling, for example.

[023] In a preferred embodiment of the invention, the axis of the annular electron outlet window cylinder is oriented vertically so that, for example, the bulk material to be exposed to accelerated electrons can fall freely within the second annular free space between the cylindrical protective grid and the electron reflector. The cylindrical protective grid keeps the falling bulk material away from the electron outlet window and thus protects it from mechanical damage caused by the bulk material. Since it is not always possible, especially in a mobile system, to orient a system so that the cylinder axis is completely vertical, the orientation of the cylinder axis of the annular electron outlet window can deviate from the vertical by an angle of approximately 10° or less, including in the handling of bulk material.

[024] The invention is described in more detail with reference below, using an exemplary embodiment. Brief description of the figures: Figure 1 is a schematic representation of a horizontal segment of an apparatus according to the invention; Fig. 2 is a schematic representation of a vertical segment of the apparatus according to the invention shown in Fig. 1; Petition 870250091419, dated 07 / 10 / 2025, page 22 / 53 10 / 28 Fig. 3 is a schematic representation of a vertical segment of a first alternative apparatus according to the invention; Fig. 4 is a schematic representation of a vertical segment of a second alternative apparatus according to the invention, including a container for receiving bulk material particles; Fig. 5 is a schematic representation of a top view of the container for receiving bulk material particles of Fig. 4; and Fig. 6 is a schematic representation of a vertical section of a third alternative apparatus according to the invention.

[025] In Figs. 1 and 2, the same apparatus 100 according to the invention is shown schematically, with Figure 1 showing a horizontal section and Figure 2 showing a vertical section. The apparatus 110 includes a cylindrical housing 101 that encloses an evacuable space. A vacuum can be maintained within the evacuable space by means of at least one vacuum pump, which is not shown in the figures for clarity, but is known from the prior art. A wall region of the housing 101 is incorporated as a cylindrical electron outlet window 102. The cylindrical electron outlet window 102 has a circular cross-section and a vertically oriented cylindrical axis 103 and encloses a centrally arranged cathode 104a. The cathode 104a is rod-shaped, extends along the cylindrical axis 103 and consists of a wire through which an electric current flows.The cathode material 104a may comprise, for example, at least one of the chemical elements tungsten or tantalum. The cathode 104a is heated by the current flow, which, in turn, leads to the thermal emission of electrons. The cathode 104a is therefore incorporated as a hot cathode. The electrons emitted by the cathode 104a are accelerated radially outwards, towards the cylindrical electron exit window 102, because the cylindrical electron exit window 102 has an anodic electrical potential. For this purpose, the cylindrical electron exit window 102 is... Petition 870250091419, dated 07 / 10 / 2025, page 23 / 53 11 / 28 is electrically connected to the positive pole of a first power supply, and cathode 104 is connected to the negative pole of the first power supply. For clarity, the first power supply is not shown in the figures. Apparatus 100 is therefore incorporated as a cylindrical electron beam generator that generates a ring of accelerated electrons, whose movements are directed radially outwards.

[026] However, the conformation of the cathode of an apparatus according to the invention as a thin wire, as is done in cathode 104a, also entails additional requirements. The high operating temperature of the wire, necessary for the thermal emission of electrons, leads to recrystallization of the wire material and changes in the wire length. If made of metal, an increase in temperature generally results in an extension of the wire. However, the extension of a wire firmly attached vertically leads to its compression and bending, so that it no longer extends exactly along the axis of the cylinder 103, which can adversely affect the homogeneity of the circumferential emission of electrons and, ultimately, the dose distribution in the material to be treated. The embrittlement of a metallic wire, which is also associated with recrystallization, can even cause rupture as a result of this compression, especially under alternating thermal stress.As an alternative to metal wire, carbon fibers can also be used as a hot cathode, so that the hot cathode is in the form of a wire. However, these carbon fibers contract with increasing temperature. If tightly fastened, high tensile stresses will develop, which would cause the hot cathode to crack.

[027] Therefore, it is advisable to firmly attach a hot cathode in the form of a wire, ribbon, rod, ring or cylinder, for example, only at the upper end, while at the lower end it is guided radially, but mounted so that it can move axially. When the apparatus is operated vertically, the upper end corresponds to the end furthest from the direction of action of the Petition 870250091419, dated 07 / 10 / 2025, p. 24 / 53 12 / 28 Earth's gravitational vector. It is advantageous to establish contact with the hot cathode at the lower end using a gripping piece which, due to its weight, always maintains a moderate tensile tension, sufficient to tighten the cathode wire but preventing it from flowing or cracking. Alternatively, the hot cathode can be securely clamped or supported only at the lower end and contacted at the upper end with an axially movable gripping piece. When the apparatus is operated vertically, the lower end corresponds to the end closest to the direction of action of the Earth's gravitational vector.

[028] If a hot cathode is heated directly by a current flow, an electric potential gradient is created in the longitudinal direction. This causes a change in the intensity of the electric field and therefore in the emission of electrons in the longitudinal direction of the hot cathode. In order to obtain a more uniform distribution of electron emission along the longitudinal extent of the hot cathode, the potential gradient must be minimized. To do this, a hot cathode can also be heated indirectly (for example, by means of thermal conduction, thermal radiation or electron impact).

[029] For this purpose, in an advantageous embodiment, a heating element in the form of a bar, ribbon or wire is arranged within a hot cylindrical cathode, centered along the cylindrical axis of the hot cylindrical cathode and electrically isolated from the cylinder wall, and heated by means of current flow. The heating element must be operated at a high temperature so as to heat the hot cathode to the emission temperature and, therefore, is made of a material with a high melting point (greater than 1500 K). Refractory metals (such as tungsten, tantalum or molybdenum) or carbon fibers are suitable for this purpose.

[030] In an early variant of this embodiment, a material resistant to high temperatures and electrically poorly conductive (such as boron nitride or oxide) Petition 870250091419, dated 07 / 10 / 2025, p. 25 / 53 A 13 / 28 zirconium plug is inserted between the central heating element and the hot cylindrical cathode, and heat from the central heating element is transferred to the hot cylindrical cathode by thermal conduction.

[031] In a second variant of the aforementioned embodiment, the heating element and the hot cathode are mounted without contact, and the heat from the central heating element is transferred to the cylindrical hot cathode by means of thermal radiation. A particularly advantageous embodiment of this variant is obtained if the central heating element and the cylindrical hot cathode are electrically connected to each other at one end and the current is returned through the heating element through the cylindrical wall of the cylindrical hot cathode. This results in a compensation of the magnetic field associated with the heating current, which negatively affects electron propagation (i.e., their extinction in the external environment of the hot cathode). The cylindrical wall of the hot cathode is sufficiently thick so as to exhibit low electrical resistance and thus the potential gradient in the longitudinal direction remains low, as desired.This results in a more homogeneous extraction field around the emission surface of the hot cylindrical cathode and, therefore, in a more uniform electron emission distribution along the longitudinal axis of the hot cathode.

[032] In a third variant of the embodiment mentioned above, the heating element and the hot cathode are also mounted without contact and completely electrically isolated from each other. The hot cathode can then be connected to the positive terminal and the heating element to the negative terminal of an additional power supply. If the heating element is heated to the emission temperature, the electrons emitted by it are attracted to the inner wall of the hot cathode and heat it by electron impact.

[033] In all three variants described, it is advisable that the hot cylindrical cathode be made of a material with a high melting point (greater than 1500 Petition 870250091419, dated 07 / 10 / 2025, page 26 / 53 14 / 28 K) and moderate to low work function (less than 5 eV). Suitable materials for this purpose include refractory metals (tungsten, tantalum, molybdenum, niobium), titanium, zirconium or stainless steel, all of which can be coated with compounds (such as oxides) in order to reduce the work function of the electrons, as well as ceramics with high melting points (such as rare earth borides, with lanthanum hexaboride being the best known representative).

[034] Indirect heating of a hot cylindrical cathode also produces a change in its length. With such geometry, it is advisable to clamp or support the hot cathode at the lower end and allow for tension-free length compensation by means of axially movable and radially guided upper clamping and contact.

[035] Furthermore, it is desirable that all embodiments of a hot cathode provide radial adjustment capability of the upper and lower gripping and contact points, so as to obtain an ideal orientation of the hot cathode along the axis of the vertically oriented cylinder 103 and thus a uniform field intensity and a resulting uniform electron emission along the entire circumference of the cathode.

[036] In apparatus 100, the cathode 104a is additionally surrounded by a cylindrical control grid 104b having a diameter that is smaller than the diameter of the cylindrical electron output window 102. The structure of the cylindrical control grid 104b is fully formed. The cylindrical control grid 104b is made of an electrically conductive material, is transparent to electrons, and has an electrical voltage potential that is slightly more positive than the electrical voltage potential of the cathode 104a. In one embodiment, the cylindrical control grid 104b has a differential voltage from the cathode 104a of approximately +20 V to approximately +2000 V. The voltage potential for the cylindrical control grid can be supplied by means of a separate second power supply unit or, alternatively, by Petition 870250091419, dated 07 / 10 / 2025, page 27 / 53 15 / 28 means a second channel controllable separately from the first power supply unit. As an electron-transparent screen cylinder, the cylindrical control grid 104b reduces the electric field intensity inside the screen cylinder, allows the installation of optional supports for the cathode wire along the longitudinal extension, and ensures uniform electron extraction on all sides, which is tolerant, within certain limits, even to positional deviations of the cathode wire, regardless of the accelerating voltage acting in the external space. Furthermore, the ability to adjust the voltage difference between the control grid and the cathode offers, in addition to varying the heating current flowing through the cathode wire, a second, quite dynamic option for controlling the emitted electron current. A similar cylindrical control grid, in combination with a cathode wire, is already known in ribbon emitters of the prior art.In the case of basic elements for holding the cathode wire and the cylindrical control grid 104b in an apparatus according to the invention, it is therefore also possible to resort to constructive solutions that are known from ribbon emitters of the prior art, for example, from document DE 196 38 925 C2.

[037] The cylindrical electron outlet window 102 may optionally have a support grid known from the prior art, which provides the cylindrical electron outlet window 102 with the necessary mechanical stability. Similarly, this support grid may include water cooling, as known from the prior art. For clarity, the figures describing the invention also do not show such a support grid.

[038] The apparatus 100 according to the invention further includes a cylindrical protective grid 105, which encloses the cylindrical electron outlet window 102, and an electron reflector 106, which in turn encloses the cylindrical protective grid 105. The electron reflector 106 is designed as a hollow cylinder. The cylinder axes of the cylindrical protective grid 105 and the electron reflector 106 are identical to the axis Petition 870250091419, dated 07 / 10 / 2025, page 28 / 53 16 / 28 cylindrical 103 of the cylindrical electron exit window 102, such that the cylindrical protective grid 105 defines a first annular free space 107 between the cylindrical electron exit window 102 and the cylindrical protective grid 105, and the electron reflector 106 defines a second annular free space 108 between the cylindrical protective grid 105 and the electron reflector 106. The height extensions of the cylindrical protective grid 106 and the electron reflector 106 extend at least over a region opposite to the height extension of the cylindrical electron exit window 102. For example, atmospheric conditions can form both within the first annular free space 107 and within the second annular free space 108.

[039] As explained above, the cylindrical electron outlet window 102 has an anodic electrical potential, so that the electrons emitted by the cathode 104a, through which the current flows, are initially accelerated towards the cylindrical electron outlet window 102. Upon exiting the cylindrical electron outlet window 102, the accelerated electrons pass through the first annular free space 107, the cylindrical protective grid 105 and, in the second annular free space, impinge on the bulk material to be exposed to the accelerated electrons. The particles of the bulk material move in free fall through the second annular free space 108, also known as the treatment area.At least in the region of the electron reflector 106 that opposes the cylindrical electron outlet window 102, the electron reflector 106 consists, at least internally, of a material that reflects electrons, so that the accelerated electrons that strike the electron reflector 106 can be reflected and fed back to the particles of the bulk material that will be exposed to the electrons.

[040] Due to the energy input into the electron reflector 106, resulting from the collision of the accelerated electrons with the electron reflector 106, the electron reflector 106 includes water flow channels (not shown in the figures for clarity), through which the thermal energy introduced into the electron reflector is dissipated. Petition 870250091419, dated 07 / 10 / 2025, page 29 / 53 17 / 28 This also simultaneously cools the air slightly in the treatment area. Such cooling channels can, for example, be attached to the outside of electron reflector 106.

[041] The cylindrical protective grid 105, which delimits the first annular space 107 to the outside, keeps the guided bulk material through the treatment area away from the cylindrical electron outlet window 102 and thus reduces the risk of the bulk material to be treated with electrons causing mechanical damage to the cylindrical electron outlet window 102. The first annular free space 107 is therefore also referred to below as the protective area. The cylindrical protective grid 105 extends along the axis of the cylinder 103 at least over a region opposite the cylindrical electron window and preferably consists of an electrically conductive and heat-resistant material, such as, for example, molybdenum or stainless steel. In one embodiment, the cylindrical protective grid 105 is designed to have transparency of at least 75% with respect to the accelerated electrons.This ensures that a sufficient number of electrons reach the bulk material to be exposed to electrons in the treatment area.

[042] Although the cylindrical protective grid 105 ensures that larger particles of the bulk material to be exposed to electrons are kept away from the electron outlet window 102, the bulk materials usually also include dust particles that can pass through the protective grid 105 and deposit on the electron outlet window 102, causing it to absorb significantly more electron energy in the contaminated regions and become thermally overloaded and destroyed.

[043] This risk of damage would become increasingly noticeable the longer the cylindrical electron source and all the components described above are formed; however, this is the key to achieving higher dose rates.

[044] According to the invention, the apparatus 100, therefore, also includes a Petition 870250091419, dated 07 / 10 / 2025, p. 30 / 53 18 / 28 series of gas tubes 109 extending within the first annular free space 107 parallel to the axis of the cylinder 103 of the cylindrical electron outlet window 102. With their orientation described above, the gas tubes 109 represent, as a module, the component that makes possible the free scalability of the axial length (vertical extension) of the cylindrical electron source and the components determining its function, which is desirable for higher dose rates. In a preferred embodiment, all gas tubes 109 are spaced by an identical first dimension from the cylindrical axis 103 of the cylindrical electron outlet window 102 and by an identical second dimension from a respective adjacent gas tube 109. In the embodiment described in the example, the gas tubes 109 have a rectangular cross-section.Alternatively, however, other geometric shapes for the cross-section of the gas tubes 109, such as a circular cross-section, can also be realized. Each gas tube 109 has holes 110 in two opposite wall regions along the longitudinal extent of the gas tubes 109, through which a first gas can be introduced into the first annular free space 107. The holes, which are formed in the gas tubes 109 with a preferred diameter of approximately 1 mm or less, extend at least over a region of the length of the gas tube that is opposite the cylindrical electron outlet window 102 and therefore corresponds to the height of the cylindrical electron outlet window 102.Holes 110 are preferably inserted into gas tubes 109, and the gas tubes 109 are oriented so that the direction of exit of the first gas through a hole 110 runs within a horizontal plane of the apparatus 100 and is oriented perpendicularly to a straight line 111 that is drawn from the axis of the cylinder 103 of the cylindrical electron outlet window 102 to the center of a horizontal interface of an associated tube 109. Arrows in Fig. 1 illustrate the direction of exit of the first gas through the holes 110. For example, air or an inert gas may be used as the first gas. For completeness, it should be mentioned that the gas tubes 109... Petition 870250091419, dated 07 / 10 / 2025, p. 31 / 53 19 / 28 are connected via a piping system to a reservoir within which the first gas is located. The reservoir may also include ambient air from an apparatus according to the invention.

[045] Instead of individual holes 110, a vertical slit may alternatively be inserted into the walls of the gas tubes 109, in opposite wall regions of the gas tubes 109, and extending over the height of the electron outlet window 102. The vertical slit has a width of approximately 1 mm or less.

[046] The first gas introduced into the protection area through the holes 110 escapes to the outside through the cylindrical protective grid 105 and is discharged into the treatment area with the flow of bulk material to be exposed to the accelerated electrons. The first gas flowing through the holes 110 performs two tasks. Firstly, the first gas penetrating outwards through the cylindrical protective grid 105 prevents dust particles from passing inwards through the cylindrical protective grid 105 towards the electron outlet window 102, thus protecting the electron outlet window 102 from a parasitic layer of dust particles. The first gas is therefore also called the protective gas. Secondly, the flow of the protective gas within the first annular free space 107 simultaneously cools the cylindrical electron outlet window 102.As a result, the water cooling of a support grid for the electron output window 102 can also be scaled to a smaller size.

[047] It is advantageous that the gas tubes 109 be in mechanical contact with the cylindrical protective grid 105 or that the gas tubes 109 be mechanically connected to the cylindrical protective grid 105. This mechanically stabilizes the cylindrical protective grid 105 and keeps it in position. The gas tubes 109 and the cylindrical protective grid are then designed, for example, as a compact assembly that can be removed entirely during maintenance.

[048] In another embodiment, the diameter of the cylindrical protective grid Petition 870250091419, dated 07 / 10 / 2025, page 32 / 53 20 / 28 105 is selected so that its cylindrical wall is centrally arranged between the electron reflector 106 and the cylindrical electron outlet window 102.

[049] In another embodiment, the annular width of the first annular free space 107 is selected so that the gas tubes 109 occupy at least 90% of the distance between the cylindrical electron outlet window 102 and the cylindrical protective grid 105.

[050] However, a disadvantage of using gas tubes 109 in an apparatus according to the invention is that gas tubes 109 are not sufficiently transparent to accelerated electrons. Therefore, each of the gas tubes 109 ensures that, in an angular range with an angle ω, a sufficient number of accelerated electrons, originating from the cathode 104a, cannot reach the second annular free space directly, or in other words, each of the gas tubes 109 ensures that the treatment area is shaded in the angular region with the angle ω relative to the accelerated electrons. These angular regions with the angle ω are therefore also referred to below as shading angle regions. Within the shading angle regions, it is impossible to subject bulk material particles to the necessary dose of accelerated electrons. Therefore, bulk material to be exposed to accelerated electrons must be prevented from entering the shading angle ranges of the treatment area.At the top of the second annular free space 108, into which the bulk material to be exposed to accelerated electrons is introduced into the treatment area, it is possible, for example, by means of mechanical diaphragms, to prevent the particles of bulk material to be exposed to accelerated electrons from entering the shading angle regions. In order to ensure the economical operation of an apparatus according to the invention, the number of gas tubes 109 and their cross-sectional dimensions must be selected so that the sum of all shading angle bands of the second annular free space 108 does not cover more than 20% of the cross-sectional area. Petition 870250091419, dated 07 / 10 / 2025, page 33 / 53 21 / 28 transversal of the second annular free space 108.

[051] Since these shading angle regions are unfortunately not avoidable in an apparatus according to the invention, but are unavoidable, it is advantageous that other components of an apparatus according to the invention that also cause shading of the treatment area or that should not be exposed to the accelerated electrons be arranged directly within the shading angle ranges. For example, it is advantageous that vertically extending electrical lines, for example, to sensor elements or measuring devices, vertically extending cooling water lines to the support grid of the cylindrical electron outlet window 102, or fastening elements for components of the apparatus according to the invention be arranged within the shading angle regions.

[052] From the shading angle regions, for example, bar or strip shaped sensor elements can be projected as antennas in the angular regions traversed by accelerated electrons and can be used to determine the circumferential and / or vertical distribution of electron current density. The actual values ​​recorded by the sensor elements are sent to an evaluation device and compared with a target value within the evaluation device. The electrical parameters of the apparatus can then be controlled depending on the result of the comparison.

[053] Alternatively or additionally, sensors, for example, in the form of metal plates electrically isolated from grounding, can also be affixed to the inner wall of the electron reflector 106, and can detect parameter values ​​of the electrons incident there and forward these values ​​to the evaluation device, in order to make statements about the circumferential and / or vertical distribution of electron current density and initiate control processes dependent on this. Petition 870250091419, dated 07 / 10 / 2025, page 34 / 53 22 / 28

[054] For reasons of energy efficiency and reduction of the thermal load of the electron source, it is advantageous not to allow electrons to impinge on the electron exit window or its vertical support and cooling structures within the shading angle regions, as these would be absorbed and thus contribute to parasitic heating of the electron beam generator, but not to its technological dose rate. For this purpose, the cylindrical control grid 104b and / or the electron exit window 102 can be designed so that they are not fully transparent to electrons, but instead are provided with defined opening regions that are aligned with the angular regions of the electron exit window 102, which are not covered by the shading angle regions with angle ω.The electrons emitted by the hot cathode and incident on the control grating 104b in the closed region of the shading angle are absorbed there and do not strike the electron exit window 102. Since they pass through only a small potential difference and therefore absorb little energy, this beamforming absorption in the control grating does not constitute a serious loss factor.

[055] In another embodiment of the invention, the electron reflector 106 is electrically isolated from the grounding electrical potential. A suitable electrical voltage potential for ignition and for maintaining a plasma at atmospheric pressure within the second annular free space 108 can be generated in the electron reflector 106 by means of a third power supply device. It is particularly advantageous to select the voltage difference so that a non-independent luminescent discharge, supported by the electrons of the beam, forms in the second annular free space 108. This is distinguished by being stabilized as a large area and uniform volume discharge, i.e., its transformation into a filament or arc discharge can be avoided. This requires a voltage of 1 kV to 5 kV per 1 cm radial distance between the electron reflector 106 and the protective grid 105. A power density Petition 870250091419, dated 07 / 10 / 2025, page 35 / 53 23 / 28 A particularly high concentration of this plasma at atmospheric pressure is achieved when the power supply is pulsed by the third power supply device. Plasmas are known not to have a deep-acting effect, but rather at least near-surface chemical and disinfectant effects on the media impacted by the plasma. A plasma inherently acts on an object, such as a particle of bulk material, on all sides. In an apparatus according to the invention, if the bulk material to be exposed to accelerated electrons is in the form of seeds, for example, where the microorganisms adhering to the seeds must be neutralized by means of the accelerated electrons, the formation of such a plasma within the second annular free space is particularly advantageous. The near-surface action of the plasma on all sides of the seeds helps to inactivate the microorganisms adhering to the seeds and disinfect them.

[056] It has already been explained that an apparatus according to the invention may have a cooling device by means of which the electron reflector 106 of an apparatus according to the invention, and thus also the second annular free space 108, may be cooled. In particular, when bulk materials within the second annular free space 108 are to be exposed to accelerated electrons, a cooling device for the electron reflector 106 alone is insufficient to prevent heating of the second annular free space 108. If the bulk material is in the form of seeds, for example, heating of the second annular free space 108 may lead to thermal damage to the seeds. In Fig. 3, an alternative apparatus 300 according to the invention is shown schematically in vertical section. The apparatus 300 initially comprises all the components and their functionalities as described for the apparatus 100 in Figs. 1 and 2.Furthermore, device 300 includes at least one device 312 for forming a flow 313 of a second gas within the second free space 108. Device 312 may be designed, for example, as a blower or fan. The flow 313 of the second gas is oriented. Petition 870250091419, dated 07 / 10 / 2025, page 36 / 53 24 / 28 so that it is identical to the direction of movement of the bulk material, which is guided through the second annular free space 108 and there exposed to accelerated electrons. The flow 313 of the second gas essentially performs two tasks. Firstly, blockages within the second annular free space 108 are avoided if the medium to be exposed to accelerated electrons is designed as a bulk material, so that the second annular free space 108 is virtually permanently purged by the flow 313 of the second gas. The second gas is therefore also called the purge gas. Secondly, a constant gas exchange within the second annular free space 108 prevents heating of the second annular free space 108. For example, air or an inert gas can be used as a second gas.

[057] In apparatus 300, the device 312 for generating the flow 313 of a second gas is arranged in the inlet region of the second annular free space 108 and is designed as a blower or fan. Alternatively or additionally, however, such a device may also be arranged at the outlet of the second annular free space 108 and designed there, for example, as a suction pump, so that, by means of the suction pump, a suction flow is generated within the second annular free space 108 and, by means of the same, air is drawn out of the second annular free space 108.

[058] It is important that the volumetric flow rate of the first gas into the first annular free space 107 can be measured independently of the flow rate 313 of the second gas within the second annular free space 108. In this way, an aerodynamic balance of the two gas flows can be achieved and it is possible to suppress the transfer of particles, for example, dust or grains of sand, from the second annular free space 108 to the first annular free space 107.

[059] Fig. 4 schematically shows a vertical section of a second alternative apparatus 400, by means of which particles of bulk material 414 are to be exposed to accelerated electrons. Initially, apparatus 400 may include all the Petition 870250091419, dated 07 / 10 / 2025, page 37 / 53 25 / 28 components and their functionalities, as described for apparatus 100 and 300 of Figs. 1, 2 and 3. The cylindrical shaft 103 of the cylindrical electron output window of apparatus 400 is oriented vertically. An apparatus for separating bulk material particles 414 is additionally arranged above the cylindrical electron beam generator with the cylindrical housing 101. The apparatus for separating bulk material particles 414 includes a container for receiving the bulk material particles 414. The container, in turn, comprises a cylindrical side wall 415 and a conical bottom wall 416, where an annular gap 417 is formed between the cylindrical side wall 415 and the conical bottom wall 416. Alternatively, the bottom wall of the container may also be disc-shaped.Due to the inclination of the bottom wall, a conical bottom wall has the advantage that the bulk material particles are set in rolling motion, which then continues as rotational motion in free fall. The container is shown schematically in plan view in Fig. 5. The conical tip of the conical bottom wall is directed upwards and positioned exactly on the axis of the extended cylinder of the cylindrical electron outlet window 103. Due to the conical shape of the bottom wall 416, the bulk material particles 414 in the lower region of the cylinder 415 are forced into an outer annular region in which the bulk material particles 414 fall through the gap in the form of the annular gap 417.The annular gap 417 is arranged rotationally symmetrically around the axis of the elongated cylinder 103 of the cylindrical electron exit window and has a gap width such that, relative to the gap width, only one particle of bulk material 414 after another can fall through the annular gap 417. Relative to the length of the annular gap 417, several particles of bulk material 414 can, of course, fall through the annular gap 417 at the same time.

[060] In one embodiment, the cylindrical wall 415 of the container and the electron reflector 106 of the electron beam generator form a continuous unit, of Petition 870250091419, dated 07 / 10 / 2025, page 38 / 53 26 / 28 so that both components are combined to form a single continuous hollow cylinder.

[061] In the angular regions of the annular gap 417, which are identical to the shading angle regions of the second annular free space with angle ω, the annular gap 417 is provided with openings 518, which prevent particles of bulk material 414 from falling through the annular gap 417 in these angular regions. Optionally, the openings 518 may have side walls that extend vertically downwards, which extend downwards through the second annular free space, fully ensuring that no particles of bulk material 414 can enter the shading angle regions.

[062] In this way, a thin annular curtain of descending bulk material particles is created and is interrupted only in the shading angle regions and can then be exposed to accelerated electrons within the second annular free space.

[063] Due to the gravitational acceleration of the falling bulk material particles, their velocity increases continuously as they traverse the second annular free space, so that the electron dose acting on the bulk material particles decreases continuously during their free fall through the second annular free space. An additional flow of a second gas within the second annular free space, as described for apparatus 300 in Fig. 3, can further increase the velocity of the falling bulk material particles and thus further reduce the electron dose acting during the fall of the bulk material particles.Furthermore, the shielding gas also passes through the cylindrical shielding grid to the second annular free space and must be discharged downwards along with the bulk material flow, so that the volumetric flow of both gases is discharged downwards, so that, with a constant cross-sectional area of ​​the second annular free space, the gas flow velocity and therefore the... Petition 870250091419, dated 07 / 10 / 2025, page 39 / 53 27 / 28 unwanted acceleration of bulk material flow within the second annular free space also increases.

[064] In Figure 6, a third alternative apparatus 600 according to the invention is shown schematically in vertical section. Apparatus 600 differs from the apparatuses described above only in that the electron reflector 606 is not designed as a hollow cylinder, but rather by the shape of the outer surface of a truncated cone, so that the second annular free space 608 has an annular shape, in which the outer diameter and therefore the cross-sectional area increase continuously towards the bottom. This configuration of the second annular free space 608 neutralizes the increase in the downward flow velocity of the protective and cleaning mixture within the second annular free space 608 and thus avoids further acceleration of the bulk material particles.

[065] An increase in the downward flow rate within the second annular free space in an apparatus according to the invention can also be neutralized if openings are introduced in the wall of the electron reflector 106 or 606, through which the gas can escape horizontally from the second annular free space, thus reducing the vertical flow rate within the second annular free space. The partial horizontal flow should be sized so that the predominantly vertical falling direction of the bulk particles is little affected, but that dust and sand are effectively transported radially outwards.

[066] Electron beam generators are known from the prior art and also generate a ring of accelerated electrons; however, their movements are directed radially inward. This also allows an annular curtain of falling bulk particles to be exposed to the accelerated electrons. However, with the same diameters of this bulk material curtain, an electron beam generator according to the invention with radially outward-directed electron propagation is significantly more compact than a beam generator. Petition 870250091419, dated 07 / 10 / 2025, pp. 40 / 53 28 / 28 electron beam generator similar to the prior art. In the electron beam generator of the prior art, all essential components (which determine the function and cost of the electron beam generator) are arranged outside the ring of falling bulk particles, so that they envelop the curtain of bulk material particles. In an apparatus according to the invention, however, all essential components are arranged inside the annular curtain of bulk particles. Therefore, in an apparatus according to the invention, many components can be scaled to smaller dimensions than in the case of the prior art, which is more economical. Furthermore, an apparatus according to the invention with radially divergent electron propagation can also be used inside hollow bodies, for example, to treat the inner wall of a tube.The axial orientation of the shielding gas tubes, sensor cables, and cooling channels, and their arrangement in the same regions as the shading angle, additionally allows for free axial scaling of the electron beam generator and, therefore, of the dose rate of a device according to the invention. Petition 870250091419, dated 07 / 10 / 2025, pp. 41 / 53

Claims

1 / 5 CLAIMS 1. Apparatus for exposing bulk material to accelerated electrons, comprising a cylindrical electron outlet window (102) as a component of a cylindrical housing (101) enclosing an evacuable space; at least one wire, ribbon, bar, annular or cylindrical cathode (104a), which is arranged within the evacuable space and delimited by the cylindrical electron outlet window (102), wherein a first power supply device is electrically conductively connected between the wire, ribbon, bar, annular or cylindrical cathode (104a) and the cylindrical electron outlet window, so that electrons can be emitted from the wire, ribbon, bar, annular or cylindrical cathode,annular or cylindrical (104a) and radially accelerated away from the axis of the cylinder (103) of the cylindrical electron outlet window (102) towards the cylindrical electron outlet window (102), CHARACTERIZED in that a) a cylindrical protective grid (105) enclosing the cylindrical electron outlet window (102) and defining a first annular free space (107) between the cylindrical electron outlet window (102) and the cylindrical protective grid (105); b) an electron reflector (106; 606) enclosing the cylindrical protective grid (105) and defining a second annular free space (108; 608) between the cylindrical protective grid (105) and the electron reflector (106); c) a series of gas tubes (109) extending within the first annular free space (107) parallel to the axis of the cylinder (103) of the cylindrical electron outlet window (102),wherein all gas tubes (109) are spaced by an identical first dimension from the axis of the cylinder (103) of the cylindrical electron outlet window (102) and by an identical second dimension from an adjacent gas tube (109), and wherein each gas tube (109) has holes (110) or at least a slit along the longitudinal extent of the gas tube (109) in regions of opposite walls, through which a first gas can be introduced into the first annular free space (107).

2. Apparatus according to claim 1, CHARACTERIZED in that the cathode, in the form of a wire, ribbon, bar, annular or cylindrical shape, is designed as a cold cathode.

3. Apparatus according to claim 1, CHARACTERIZED in that the cathode (104a) in wire, ribbon, bar, annular or cylindrical form is designed as a hot cathode.

4. Apparatus according to claim 3, CHARACTERIZED in that the cathode (104a) in wire, ribbon, bar, annular or cylindrical form is designed as a hot cathode heated directly by means of current flow.

5. Apparatus according to claim 3, CHARACTERIZED in that the cathode is cylindrical and has a heating element in the form of a wire, ribbon or rod extending along the axis of the cylinder, wherein the cylindrical cathode can be heated by means of thermal conduction, thermal radiation or electron impact.

6. Apparatus according to claim 5, CHARACTERIZED in that one end of the cylindrical cathode is electrically connected in a conductive manner to one end of the heating element in the form of a wire, ribbon or rod.

7. Apparatus according to any of the claims, CHARACTERIZED by a cylindrical control grid (104b) enclosing the wire-shaped, ribbon-shaped, bar-shaped, annular or cylindrical cathode (104a) and having a diameter that is smaller than the diameter of the cylindrical electron outlet window (102).

8. Apparatus according to claim 7, CHARACTERIZED in that the cylindrical control grid (104b) has a voltage difference with respect to the bar, annular or cylindrical shaped cathode (104a) of approximately +20 V to approximately +2000 V, wherein a second power supply unit generates the electrical voltage potential for the cylindrical control grid (104b).

9. Apparatus according to any one of claims 7 or 8, CHARACTERIZED in that the cylindrical control grid (104b) is not transparent to electrons throughout its circumference, but only in defined opening regions, these opening regions being arranged centrally and symmetrically to those of the cylindrical electron outlet window (102).

10. Apparatus according to any of the claims, CHARACTERIZED in that the gas tubes (109) are affixed to the cylindrical protective grid (105).

11. Apparatus according to any of the preceding claims, CHARACTERIZED in that at least one device (312) for generating a flow (313) of a second gas within the second annular free space (108).

12. Apparatus according to any of the preceding claims, CHARACTERIZED in that the volumetric flow of the first gas into the first annular free space (107) can be measured independently of the flow (313) of a second gas within the second annular free space (108).

13. Apparatus according to any of the preceding claims, CHARACTERIZED in that the electron reflector (106) is electrically isolated from the grounding electrical potential, and a third power supply device generates an electrical voltage potential in the electron reflector (106) for ignition and maintaining a plasma within the second annular free space (108).

14. Apparatus according to any of the preceding claims, CHARACTERIZED in that the cylindrical axis (103) of the cylindrical electron outlet window (102) is oriented vertically or at an angle of approximately 10° or less, deviating from the vertical. Petition 870250091419, dated 07 / 10 / 2025, page 44 / 53 4 / 5 15. Apparatus according to any of the preceding claims, CHARACTERIZED in that a device for separating and rotating a plurality of particles of bulk material (414), comprising a cylindrical side wall (415) and a disc-shaped or conical bottom wall (416), wherein an annular gap (417) is formed between the cylindrical side wall (415) and the disc-shaped or conical bottom wall (416).

16. Apparatus according to any of the preceding claims, CHARACTERIZED in that the electron reflector (106, 606) is designed as a hollow cylinder (106) or in that the electron reflector (106, 606) has the shape of the outer surface of a truncated cone (606).

17. Apparatus according to any of the preceding claims, CHARACTERIZED in that the electron reflector (106; 606) has openings in the wall.

18. Apparatus according to any one of claims 1 to 17, CHARACTERIZED in that the cathode (104a), in the form of a wire, in the form of a ribbon, in the form of a bar, annular or cylindrical shape, is firmly attached only at the upper end and contacted at the lower end with an axially movable gripping piece.

19. Apparatus according to any one of claims 1 to 17, CHARACTERIZED in that the cathode (104a) in the form of a wire, in the form of a ribbon, in the form of a bar, annular or cylindrical shape is firmly attached or supported only at the lower end and contacted at the upper end with an axially movable gripping piece.

20. Apparatus according to any of the preceding claims, CHARACTERIZED in that the radial position of the cathode (104a) in wire, ribbon, bar, annular or cylindrical form is adjustable.

21. Apparatus according to any of the preceding claims, Petition 870250091419, 07 / 10 / 2025, p. 45 / 53 5 / 5 CHARACTERIZED in that the cylindrical electron outlet window (102) is designed so that it is not totally transparent to electrons, but is provided with defined opening regions that are aligned with the angular regions of the electron outlet window (102) and that are not covered by shading angle regions with angle ω.

22. Apparatus according to any of the claims, CHARACTERIZED in that openings covering the second annular free space (108) on its upper side in regions of the shading angle with the angle ω. Petition 870250091419, dated 07 / 10 / 2025, p. 46 / 53

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