WO2015049014A1

WO2015049014A1 - Article irradiation system

Info

Publication number: WO2015049014A1
Application number: PCT/EP2013/072892
Authority: WO
Inventors: Jean-Louis Bol; Benoît Mullier; Markus NIEDERREITER; Josef MITTENDORFER
Original assignee: Ion Beam Applications
Priority date: 2013-10-03
Filing date: 2013-11-04
Publication date: 2015-04-09

Abstract

Irradiation system (1) for irradiating an article (5) with either an electron (201) or an X-ray (202) irradiation field and comprising: radiation means (10) for producing at least one electron beam, said irradiation system (1) being configured for directing a produced electron beam along a first electron beam path, and for directing a produced electron beam along a second electron beam path; an irradiation chamber (30) for receiving said article (5); a shielding wall (20) for shielding the irradiation chamber (30) from the radiation means (10). Said first (55) (respectively second (65)) electron beam path is configured for delivering said electron irradiation field (201) (respectively X-ray irradiation field (202)) in said irradiation chamber (30) from an opening (21; 22) in said shielding wall (20).

Description

ARTICLE IRRADIATION SYSTEM

TECHNICAL FIELD

[0001 ] According to a first aspect, the invention relates to the field of systems (or devices) for irradiating articles. More specifically, first aspect of the invention relates to an irradiation system for irradiating an article with an electron irradiation field and/or an X-ray irradiation field. According to a second aspect, the invention relates to a method for irradiating at least one article.

DESCRIPTION OF PRIOR ART [0002] Irradiation is used for treating many types of articles or products, notably for sterilizing them. For reasons of safety, irradiation systems now generally use an electron accelerator (rather than a source of gamma rays for instance) for producing beams of accelerated electrons (or beams of high- energy electrons). These beams of accelerated electrons (or electron beams) are either directed immediately to the article to treat, or passed through a foil made of a high Z material, for producing X-rays that are after conveyed to the article to treat.

[0003] EP1446812 B1 discloses an irradiation system that allows irradiating articles with either electron or X-ray irradiation fields. This irradiation system comprises a radiation source and three beam paths for irradiating articles on two separate levels (see figure 1 and [0030] for instance). Two horizontal beam paths are configured for X-ray irradiation of articles along two horizontal directions at an upper level (see also figure 2). A third beam path is directed vertically downwards for irradiating articles with electrons on a lower level.

[0004] A drawback of the irradiation system of EP1446812 B1 is that this irradiation system is large. This large size increases the costs. One indeed needs to build a large building for housing such an irradiation system. One also needs to build large shielding walls for shielding the irradiation system from the surrounding environment. SUMMARY OF THE INVENTION

[0005] According to a first aspect, it is an object of the invention to provide an irradiation system for irradiating an article with an electron irradiation field and/or an X-ray irradiation field that is smaller (or more compact). To this end, the inventors propose an irradiation system for irradiating an article with an electron irradiation field and/or an X-ray irradiation field that comprises:

- radiation means for producing at least one electron beam, said irradiation system being configured:

· for directing an electron beam produced by said radiation means along a first electron beam path, and

• for directing an electron beam produced by said radiation means along a second electron beam path;

- an electron irradiation horn positioned at an end extremity of said first electron beam path for forming said electron irradiation field;

- an X-ray irradiation horn positioned at an end extremity of said second electron beam path for transforming an electron beam produced by said radiation means and following said second electron beam path into said X-ray irradiation field;

- an irradiation chamber for receiving said article to be irradiated;

- a shielding wall for shielding the irradiation chamber from the radiation means;

- a conveyor band system for carrying said article from outside to inside said irradiation chamber.

The irradiation system of the invention is characterized in that:

- said first electron beam path and said electron irradiation horn are configured for delivering said electron irradiation field in said irradiation chamber from an opening in said shielding wall; and in that

- said second electron beam path and said X-ray irradiation horn are configured for delivering said X-ray irradiation field in said irradiation chamber from an opening in said shielding wall;

such that said article can be irradiated by said electron irradiation field and/or by said X-ray irradiation field in said irradiation chamber. Hence, the article can be irradiated by said electron irradiation field and/or by said X-ray irradiation field in a single irradiation chamber.

[0006] The irradiation system according to the invention is configured such an article can be irradiated either by an electron irradiation field or an X- ray irradiation field in a single irradiation chamber. Hence, the size of the irradiation system is reduced with respect to the irradiation system of EP1446812 B1 . For this last irradiation system, there are two (or more) irradiation chambers corresponding to the upper and lower levels. For the embodiment shown in figure 1 of EP1446812 B1 , articles can only be irradiated with X-ray irradiation fields on the upper level, and only with an electron irradiation field on the lower level. Hence, at least two irradiation chambers are needed. As the irradiation system according to the invention has only one irradiation chamber for irradiating articles with both electron and X-ray irradiation fields, its size is reduced. As a consequence, its cost of fabrication and of maintenance is also reduced. In particular, the volume of shielding walls that is required for the irradiation system according to the invention is reduced as the global size of the irradiation system is reduced. Shielding walls used for shielding X-ray irradiation fields are also able to shield electron irradiation fields as electrons penetrate matter less deeply than X- rays do. Therefore, shielding walls able to shield radiations generated by the X-ray irradiation field can also be used for shielding radiations generated by the electron irradiation field. The costs of fabrication of the irradiation system are therefore still further reduced.

[0007] The irradiation system according to the invention has other advantages. When it is desired to mainly treat boxes, it is often sufficient to use an electron irradiation field. Electrons penetrate less deeply in matter than X-rays do. However, efficiency of a treatment with X-rays is lower than the one of a treatment with electrons (a large amount of energy is notably lost in the X- ray irradiation horn that generally comprises an X-ray target or X-ray conversion means). Therefore, if it is desired to mainly treat boxes (and not pallets), one generally prefers using an electron irradiation field as boxes typically have a smaller size than pallets. The electron penetration depth is then enough and the global efficiency is better. However, when the size or the density (or both) of the articles (boxes for instance) to treat increases, it is possible that an electron irradiation field is no longer adapted for treating them. Then, one can simply impose the irradiation system of the invention to treat the article with the X-ray irradiation field. It is not necessary to send such large articles or articles of high density to another irradiation system as the one of the invention combines both electron and X-ray treatments, in particular in a same irradiation chamber. As only one irradiation system is necessary for X-rays and electrons treatment, costs and time are reduced. Handling of the irradiation system is also simplified. It is neither necessary to send the large articles or articles of high density to another level or to another irradiation chamber as it is the case with the irradiation system of EP1446812 B1 . Handling is thus also simplified with respect to the irradiation system of EP1446812 B1 . Generally, the electron irradiation field and the X-ray irradiation field are not produced at a same time with the irradiation system of the invention: only one of these two irradiation fields is generally active at a time. However, in another preferred embodiment of the irradiation system of the invention, both electron and X-ray irradiation fields can be active or produced at a same time.

[0008] Preferably, the irradiation system according to the invention further comprises:

- first directing means for directing an electron beam produced by said radiation means along said first electron beam path towards said electron irradiation horn;

- second directing means for directing an electron beam produced by said radiation means along said second electron beam path towards said X-ray irradiation horn.

Preferably, said first and second direction means comprise magnets.

[0009] Preferably, said first electron beam path, said electron irradiation horn, said second electron beam path, and said X-ray irradiation horn are configured for delivering in said single irradiation chamber said electron irradiation field and said X-ray irradiation field along two substantially parallel main directions.

The terms 'along two substantially parallel main directions' mean that an intersection angle characterizing a non-parallel property of these two main directions (when these two main directions are not strictly parallel) is preferably lower than 10° more preferably lower than 5° and still more preferably lower than 1 °. The size of the irradiation system according to the invention can be further reduced with this preferred embodiment. With respect to the irradiation system of EP1446812 B1 , only one level is necessary with this preferred embodiment as the two main directions along which electron and X-ray irradiation fields are delivered are substantially parallel.

[0010] Preferably, these two substantially parallel main directions are substantially perpendicular to a translation plane defined in said irradiation chamber by said conveyor band system and corresponding to a plane along which said conveyor band system is able to carry said article in said irradiation chamber according to a translation motion.

In the irradiation chamber, the articles are generally transported with their length L and width D parallel to said translation plane, and with their thickness t perpendicular to same translation plane (where thickness t is in general smaller than or equal to length L and width D). Then, the transport of the articles is facilitated as their largest dimensions (length L and width D) generally lie on the conveyor band system (the stability of the moving articles is then increased). With this preferred embodiment, the electron and X-ray irradiation fields are thus generally able to hit the articles along their thickness t, i.e. along their smallest dimension in general. When these articles are boxes (and not pallets), it is then often enough to use the electron irradiation field for treating them. As efficiency of a treatment with electrons is higher than efficiency of a treatment with X-rays, this preferred embodiment is particularly adapted for treating boxes. Preferably, this translation plane is horizontal with respect to ground. Then, said two substantially parallel main directions are vertical.

The size of the irradiation system can be further reduced with this last preferred embodiment. More specifically, when comparing with the irradiation device of EP1446812 B1 , one can reduce the horizontal extension of the irradiation device. As the two irradiation fields hit the articles vertically, it is no longer necessary to provide the space required for the X-rays beam paths of EP1446812 B1 that extend horizontally. Also, the conveyors of the upper level of the irradiation device of EP1446812 B1 are no longer necessary.

[0011] Preferably, these two substantially parallel main directions are such that said electron and X-ray irradiation fields are able to hit the article upwards. More preferably, these two substantially parallel main directions are such that said electron and X-ray irradiation fields are able to hit the article downwards.

[0012] Preferably, said conveyor band system comprises a single entrance conveyor for carrying said article from outside to inside said irradiation chamber. When the irradiation system comprises single entrance conveyor, its size can be further reduced. Its cost is also reduced as only one entrance conveyor is needed for carrying the article inside the irradiation chamber.

[0013] Preferably, said conveyor band system is also able to carry said article from inside to outside said irradiation chamber, and said conveyor band system comprises a single exit conveyor for carrying said article from inside to outside said irradiation chamber. When the irradiation system comprises single exit conveyor, its size can be further reduced. Its cost is also reduced as only one exit conveyor is needed for carrying the article outside the irradiation chamber.

[0014] Preferably, said conveyor band system comprises a single transport conveyor inside said irradiation chamber for moving said article inside it. A transport conveyor allows moving the articles to treat in the irradiation chamber. When the irradiation system comprises single transport conveyor, its size can be further reduced. Its cost is also reduced as only one transport conveyor is needed for moving the article in the irradiation chamber.

[0015] Preferably, said radiation means is able to produce a first and a second electron beams for respectively delivering said electron irradiation field and said X-ray irradiation field, said irradiation system being configured:

• for directing said first electron beam along said first electron beam path, and

• for directing said second electron beam along said second electron beam path.

[0016] Preferably, the radiation means of the irradiation system of the invention is able to produce:

- an electron beam whose electrons have a first mean energy, and - an electron beam whose electrons have a second mean energy, said first and second mean energies being different.

With this last preferred embodiment, it is possible to have electron beams that have a well-adapted energy for irradiating an article with electrons or X-rays. Depending on the type of the irradiation field (electron or X-ray), the most adapted energy for the electrons of the electron beams generally changes indeed.

One example of this preferred embodiment corresponds to a case where the radiation means produces two electron beams with first and second mean energy that are spatially different. That means that in this example, these two electron beams follow two different electron beam paths. Another example of this preferred embodiment corresponds to a case where the radiation means produces two electron beams with first and second mean energy that follows a same electron beam path but that are generated in different times.

[0017] Preferably, the radiation means is able to produce an electron beam whose electrons have a mean energy comprised between 5 and 12 MeV. More preferably, said radiation means is able to produce an electron beam whose electrons have a mean energy comprised between 9 and 1 1 MeV. Still more preferably, the radiation means is able to produce an electron beam whose electrons have a mean energy equal to 10 MeV. Such energies are preferably used for generating the electron irradiation field. It allows obtaining an electron irradiation field having enough penetration without activation.

[0018] Preferably, said radiation means is able to produce an electron beam whose electrons have a mean energy comprised between 6 and 8 MeV. More preferably, the radiation means is able to produce an electron beam whose electrons have a mean energy equal to 7 MeV. Such energies are preferably used for generating the X-ray irradiation field. It allows obtaining an X-ray irradiation field having enough penetration without activation.

[0019] Preferably, the radiation means is able to produce an electron beam having an energy comprised between 2 and 700 kW. More preferably, said radiation means is able to produce an electron beam having a power comprised between 9 kW and 1 1 kW, and still more preferably, a power of 10 kW. Such powers are preferably used for an electron beam used for generating the electron irradiation field.

[0020] Preferably, said radiation means is able to produce an electron beam having a power comprised between 70 kW and 90 kW, and more preferably a power of 80 kW. Such powers are preferably used for an electron beam used for generating the X-ray irradiation field.

[0021] Preferably, the irradiation system of the invention further comprises an articles characterizing unit for determining at least one value related to the size and/or the density of said article. More preferably, this articles characterizing unit is able to determine one value or several values related to both the size and the density of each article to treat. Depending on the value(s) provided by this articles characterizing unit, one can decide if an electron or an X-ray irradiation field is more adapted for treating the article that has been characterized by said articles characterizing unit. When the articles characterizing unit outputs a value (or several values) meaning that the article is large or that its density is large, or that both its size and density are large, the X-ray irradiation field is preferably used rather than the electron irradiation field. Preferably, an X-ray irradiation field is used rather than an electron irradiation field if the article to treat has an area density (or surface density) larger than 9 g/cm². However, not only size and/or density are/is a criterion for deciding to treat an article with an X-ray irradiation field rather than an electron irradiation field. For some articles, it could be indeed recommended/preferred to use an X-ray irradiation field even if its size and/or its density are/is not larger than a given threshold. This could be the case for articles having specific geometries, and for articles requiring a high quality of treatment. On another hand, one could prefer a treatment with an electron irradiation field even for large articles and/or for articles of high density.

[0022] Preferably, the irradiation system of the invention comprises a control unit for imposing that the article to treat has to be irradiated by the X- ray irradiation field rather than the electron irradiation field when the size of the article, or its density is larger than a specific value. It is also possible that this control unit uses a parameter related to both the size and the density of the article to treat for deciding to treat it with X-rays or electrons. More preferably, the size of the article to treat, its density, or both of these data are provided by the articles characterizing unit. These parameters could nevertheless by provided by a human operator that would measure them for instance.

[0023] Preferably, the article is a box. Boxes and pallets are generally parallelepipeds with a thickness t, a length L, and a width D. Then, boxes preferably have the following dimensions: 5 cm < t < 50 cm, 40 cm < L < 1 .2 m, 30 cm < D < 1 m. However, smaller or larger boxes are possible. Pallets preferably have the following dimensions: 1 m < t < 3 m (with a preferred value of 2 m), 90 cm < L < 2 m (with a preferred value of 1 .2 m), 80 cm < D < 2 m. However, smaller and larger pallets are possible. Pallets preferably have a footprint whose size is close to 1 m ^* 1 .2 m.

[0024] Contrary to the irradiation system of EP1446812 B1 , the irradiation system according to the invention is particularly well-adapted for treating boxes. The irradiation system of EP1446812 B1 is more adapted for treating pallets.

[0025] Preferably, the irradiation system further comprises lifting means or a mechanical system for imposing a rotation of 180° to an article such that the positions of its upstream and downstream boundary surfaces along said electron and X-ray irradiation fields can be inverted. This preferred embodiment allows better treating articles of relatively large thicknesses. When irradiating an article with an electron or X-ray irradiation field from above, only top portion of the article is treated uniformly when it has a large thickness. By performing a 180° rotation after a first treatment passing or first treatment stage, and thereafter performing a second treatment passing, the article can be more fully and more uniformly irradiated. Preferably, this lifting means or mechanical system is able to impose a rotation of 180° by performing two successive rotations of 90°. More preferably, this 180° rotation is performed between two treatment passes or stages. This allows irradiating different portions of a large article.

[0026] Preferably, the irradiation system further comprises control means for inverting a first and a second articles such that said first article can take the place of said second article in said irradiation chamber and vice versa. This preferred embodiment allows better treating two articles that pass under the electron or X-ray irradiation horn at a time. Treatment can be more efficient and more uniform as different portions of the two articles can be irradiated by changing the positions of the two articles between two treatment stages. Different control means that are known by the one skilled in the art can be used. For example, the control means can comprise a motor and a mechanical device for changing the positions of two articles. Such a motor is preferably a mechanical motor. Examples of such a mechanical device are: a plate that is able to push and move an article; mechanical arms that are able to pick, lift, and move an article; conveyors that are able to move an article.

[0027] Preferably, the irradiation system of the invention allows irradiating an article with vertical electron and/or X-ray irradiation fields with respect to ground. More preferably, these electron and/or X-ray irradiation fields are provided from up to down with respect to ground.

[0028] According to a second aspect, it is an object of the invention to provide a method for efficiently irradiating an article with an electron irradiation field. To this end, the inventors propose a method comprising the following steps:

- irradiating at least a portion of said article with said electron irradiation field during a first treatment passing, said article being positioned during said first treatment passing such that it presents in the irradiation chamber a first boundary surface upstream a second boundary surface along said electron irradiation field;

- thereafter imposing a rotation of 180° of said article for inverting the positions of said first and second boundary surfaces;

- thereafter irradiating at least a portion of said article with said electron irradiation field during a second treatment passing, said article being positioned during said second treatment passing such that it presents in said irradiation chamber said first boundary surface downstream said second boundary surface along said electron irradiation field.

This method allows better irradiating an article with an electron irradiation field, especially when said article has a large thickness. In particular, this method allows obtaining a more uniform treatment of the article with an electron irradiation field.

[0029] The inventors also propose a method for irradiating a first and a second articles with an X-ray irradiation field of an irradiation system according to the invention, said irradiation system comprising a conveyor band system for moving said first and a second articles along a treatment path in the irradiation chamber, said method comprising the steps of:

- positioning said first and second articles next to each other such that it is possible to define a cross-section plane perpendicular to at least a portion of said treatment path whose intersection with said first and second articles is non void, said first and second articles being also positioned such that they each present in said irradiation chamber a first boundary surface upstream a second boundary surface along said X- ray irradiation field;

- thereafter, irradiating at least a portion of each of said first and second articles with said X-ray irradiation field;

- thereafter, inverting said first and second articles such that said first article takes the place of said second article and vice versa;

- thereafter, imposing a rotation of 180° to said first and second articles for inverting the positions their first and second boundary surfaces;

- thereafter, inverting said first and second articles such that said that first article takes the place of second article and vice versa;

- thereafter, irradiating at least a portion of each of said first and second articles with said X-ray irradiation field.

This method allows better irradiating an article with an X-ray irradiation field, especially when said article has a large thickness. In particular, this method allows obtaining a more uniform treatment of the article with an X-ray irradiation field.

[0030] The inventors propose another method for irradiating a first and a second articles with an X-ray irradiation field of an irradiation system according to the invention, said irradiation system comprising a conveyor band system for moving said first and a second articles along a treatment path in the irradiation chamber, said another method comprising the steps of:

- positioning said first and second articles next to each other such that it is possible to define in said irradiation chamber a cross-section plane perpendicular to at least a portion of said treatment path whose intersection with said first and second articles is non void in said irradiation chamber, said first and second articles being also positioned such that they each present in said irradiation chamber a first boundary surface upstream a second boundary surface along said X-ray irradiation field;

- thereafter, imposing a rotation of 180° to said first and second articles for inverting the positions of their first and second boundary surfaces;

BRIEF DESCRIPTION OF THE DRAWING

[0031 ] These and further aspects of the invention will be explained in greater detail by way of examples and with reference to the accompanying drawings in which:

Fig. 1 shows a 2D schematic illustration of an irradiation system according to a preferred embodiment of the invention;

Fig. 2 shows a top view illustration of a preferred embodiment of the irradiation system according to the invention; Fig. 3 shows a cross-section of same preferred embodiment along the broken line shown in previous figure;

Fig. 4 shows a top view of an irradiation system according to another preferred embodiment of the invention;

Fig. 5 shows a 2D schematic illustration of an irradiation system according to another preferred embodiment of the invention;

Fig. 6 shows a 2D schematic illustration of an irradiation system according to another preferred embodiment of the invention;

Fig. 7 shows a top view of an example of conveyor band system in combination with an irradiation chamber, a shielding wall, a technical room, an electron irradiation horn and an X-ray irradiation horn;

Fig. 8 schematically shows with two-dimensional drawings an example of a method for efficiently irradiating an article with an electron irradiation field; Fig. 9 schematically shows an example of mechanical system for imposing a rotation of 180° to an article;

Fig. 10 schematically shows another example of mechanical system for imposing a rotation of 180° to an article when this mechanical system comprises a first and a second lifting modules;

Fig. 1 1 schematically shows with two-dimensional drawings an example of a method for efficiently irradiating an article with an X-ray irradiation field;

Fig. 12 schematically shows with two-dimensional drawings another example of a method for efficiently irradiating an article with an X-ray irradiation field. The drawings of the figures are neither drawn to scale nor proportioned. Generally, identical components are denoted by the same reference numerals in the figures.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0032] Figure 1 schematically shows a side view of an irradiation system 1 (or irradiation device) according to a preferred embodiment of the invention. The irradiation system 1 comprises radiation means 10. As shown in figure 1 , radiation means 10 is preferably a radiation source 10 able to produce a first 101 and a second 102 electron beams (or a first and a second beams of accelerated electrons). Preferably, the radiation source 10 is a Rhodotron TT100 or a Rhodotron TT200 available at IBA S.A. However, any radiation source 10 known by the one skilled in the art can be used for producing said first 101 and a second 102 electron beams. Other examples for the radiation source 10 are: LINAC (or linear particle accelerator), DC accelerator, and Dynamitron. As detailed below in relation to other preferred embodiments, radiation means 10 can comprise several radiation sources 10, each of them being preferably a radiation source chosen among Rhodotron, LINAC, DC accelerator, and Dynamitron. Other types of radiation sources 10 known by the one skilled in the art could be used.

[0033] The irradiation system 1 is configured such that said first electron beam 101 is able to follow a first electron beam path 55, and such that said second electron beam 102 is able to follow a second electron beam path 65.

[0034] The irradiation system 1 further comprises an electron irradiation horn 75 positioned at an end extremity of the first electron beam path 55 for forming an electron irradiation field 201 from said first electron beam 101 . For forming an X-ray irradiation field 202 from said second electron beam 102, the irradiation system 1 also comprises an X-ray irradiation horn 76 positioned at an end extremity of the second electron beam path 65. More specifically, this X-ray irradiation horn 76 is able to transform the second electron beam 102 into such an X-ray irradiation field 202. Such electron 75 and X-ray 76 irradiation horns are known by the one skilled in the art. X-ray irradiation horn 76 comprises X-ray conversion means 70 (not shown in figure 1 ) for transforming electrons into X-rays. Preferably, the X-ray conversion means 70 comprise a conversion window made of a foil of high-Z material (X-ray target). Preferably, this high-Z material is tantalum or tungsten.

[0035] The irradiation system 1 also comprises an irradiation chamber 30 for receiving an article 5 (or articles 5) to be irradiated or treated. A shielding wall 20 allows shielding the irradiation chamber 30 from the radiation source 10. Last, the irradiation system 1 comprises a conveyor band system 1 1 for carrying articles 5 from outside to inside the irradiation chamber 30.

[0036] First electron beam path 55 and said electron irradiation horn 75 are configured for delivering the electron irradiation field 201 in the irradiation chamber 30 from an opening 21 in said shielding wall 20. Second electron beam path 65 and said X-ray irradiation horn 76 are also configured for delivering the X-ray irradiation field 202 in the irradiation chamber 30 from an opening 22 in the shielding wall 20. Hence, an article 5 can either be irradiated by the electron irradiation field 201 or by the X-ray irradiation field 202 in a single irradiation chamber 30 with the irradiation system 1 of the invention. One could also imagine irradiating a same article 5 with both an electron irradiation field 201 and an X-ray irradiation field 202.

[0037] As shown in figure 1 , the opening 21 in the shielding wall 20 from which the electron irradiation field 201 is delivered in the irradiation chamber 30 is preferably different from the opening 22 from which the X-ray irradiation field 202 is delivered in same irradiation chamber 30. However, in another preferred embodiment, electron 201 and X-ray 202 irradiation fields are preferably delivered in the irradiation chamber 30 from a same opening in the shielding wall 20.

[0038] Preferably, the irradiation chamber 30 has only one level. This is possible with the irradiation system 1 of the invention as an article 5 can either be irradiated by the electron irradiation field 201 and/or by the X-ray irradiation field 202 in a single irradiation chamber 30.

[0039] Preferably, electron 75 and X-ray 76 irradiation horns comprise scanning magnets that are able to scan an electron beam along a line (or along one direction). Then, the electron 201 (respectively X-ray 202) irradiation field formed by the electron irradiation horn 75 (respectively X-ray irradiation horn 76) corresponds to an electron (respectively X-ray) linear field. At the exit of the electron irradiation horn 75, a linear electron irradiation field 201 is then formed, whereas at the exit of the X-ray irradiation horn 76, a linear X-ray irradiation field 202 is then formed. In this preferred embodiment, it is possible to define a main direction 301 for the linear electron irradiation field 201 , and another main direction 302 for the linear X-ray irradiation field 202. These main directions (301 , 302) correspond to mean directions of linear electron 201 and X-ray 202 irradiation fields. If the linear electron irradiation field 201 (respectively linear X-ray irradiation field 202) is delimited by two boundaries (201 a, 201 b) (respectively (202a, 202b)), main direction 301 (respectively 302) of this linear electron irradiation field 201 (respectively linear X-ray irradiation field 202) is positioned at equal distances from these two boundaries (201 a, 201 b) (respectively (202a, 202b)). Conveyor band system 1 1 is preferably able to impose a translation movement of an article 5 in the irradiation chamber 30. Scanning of an article 5 along a two- dimensional pattern is then possible thanks to such a translation movement imposed by the conveyor band system 1 1 in the irradiation chamber 30: translation movement provided by conveyor band system 1 1 then provides another direction along which articles 5 are treated. In another preferred embodiment, electron irradiation horn 75 and X-ray irradiation horn 76 are able to produce 2D irradiation fields (201 , 202).

[0040] As shown in figure 1 , the irradiation system 1 preferably comprises first directing means 50 for directing the first electron beam 101 along the first electron beam path 55 towards the electron irradiation horn 75, and second directing means 60 for directing the second electron beam 102 along the second electron beam path 65 towards the X-ray irradiation horn 76. However, the irradiation system 1 could be configured such that such first 50 and second 60 directing means are not necessary (see below in relation to the preferred embodiments shown in figures 4 and 5). When first 50 and second 60 direction means are used, they preferably comprise deflecting magnets for imposing curved trajectories (55, 65) to first 101 and second 102 electron beams. As it is shown in figure 1 , first 50 and second 60 directing means are preferably able to impose a 270° deflection to first 101 and second 102 electron beams. More preferably, first 50 and second 60 directing means are able to impose a 90° deflection to first 101 and second 102 electron beams with respect to the exit paths of first 101 and second 102 electron beams from the radiation source 10.

[0041] As it is shown in figure 1 , the electron irradiation field 201 and the X-ray irradiation field 202 are preferably delivered in the irradiation chamber 30 along two main directions (301 , 302) that are substantially parallel. More preferably, these two parallel main directions (301 , 302) are vertical, i.e. perpendicular to a horizontal plane. Preferably, such a horizontal plane corresponds to a translation plane defined in the irradiation chamber 30 and corresponding to a plane along which the conveyor band system 1 1 is able to carry the article 5 in said irradiation chamber 30 along a translation motion. Such a horizontal plane is preferably parallel to a plane into which the electrons are accelerated in the radiation source 10. As it is shown in figure 1 , the electron irradiation field 201 and the X-ray irradiation field 202 are preferably delivered along two downward main directions (301 , 302). Then, the article 5 is irradiated from its top surface.

[0042] Figures 2 shows a top view of another preferred embodiment of the irradiation system 1 of the invention. In this preferred embodiment, the radiation means 10 also comprises a radiation source 10 that is able to produce a first 101 and a second 102 electron beams. As shown in this figure, first 101 and second 102 electron beams preferably exit the radiation source 10 according to two linear paths that are separated by an a angle. Generally, a angle depends on the type of radiation source 10 and on the electron energies of first 101 and second 102 electron beams. Preferably, a angle is comprised between 100° and 160°. More preferably, a angle is equal to 120°.

[0043] Figure 3 shows a cross-section of the preferred embodiment shown in figure 2 along the broken line shown in same figure 2. In this preferred embodiment, the radiation source 10 is separated from the irradiation chamber 30 by a concrete shielding wall 20. Electron irradiation horn 75 is located in a first opening 21 of the shielding wall 20, whereas X-ray irradiation horn 76 is located in a second opening 22 of the shielding wall 20. X-ray irradiation horn 76 comprises X-ray conversion means 70 for producing X-rays from the electrons of the second electron beam 102. X-ray conversion means 70 preferably comprise a conversion window made of a foil of high-Z material located at an extremity of the second scan horn 76.

[0044] Figure 4 shows a top view of another preferred embodiment of the invention. In this preferred embodiment, the irradiation system 1 also comprises a single radiation source 10 that is able to deliver two electron beams (101 , 102). No direction means (such as first 50 and second 60 directing means of figures 1 -3) is necessary with this preferred embodiment. The irradiation system 1 is configured for directing a first electron beam 101 along a first electron beam path 55, and configured for directing a second electron beam 102 along a second electron beam path 65 without the need of any direction means. First 55 and second 65 electron beam paths are horizontal in this preferred embodiment. [0045] Figure 5 shows a 2D schematic illustration of the irradiation system 1 according to another preferred embodiment of the invention. In this preferred embodiment, the radiation means 10 comprises two radiation sources 10. A radiation source 10 is able to produce a first electron beam 101 ; another radiation source 10 is able to produce a second electron beam 102. All types of radiation sources for producing electron beams that are known by the one skilled in the art can be used for the two radiation sources 10 of this preferred embodiment. The irradiation system 1 is configured for directing first electron beam 101 along a first electron beam path 55, and for directing second electron beam 102 along a first electron beam path 65. As explained for the preferred embodiments shown in figures 1 -3, the irradiation system 1 also comprises electron (75) and X-ray (76) irradiation horns for obtaining electron (201 ) and X-ray (202) irradiation fields. A shielding wall 20 for shielding an irradiation chamber 30 from the two radiation sources 10 has two openings (21 ; 22) for irradiation an article 5 with said electron (201 ) and/or X- ray (202) irradiation fields. This preferred irradiation system 1 also comprises a conveyor band system 1 1 for carrying the article from outside to inside the irradiation chamber 30.

[0046] Figure 6 shows a 2D schematic illustration of the irradiation system 1 according to another preferred embodiment of the invention. In this preferred embodiment, the radiation means 10 comprises one radiation source 10. All types of radiation sources for producing electron beams that are known by the one skilled in the art and that have been cited before can be used. The radiation source 10 of the preferred embodiment of figure 6 is able to produce one electron beam 101 . This preferred irradiation system 1 is configured for directing this electron beam 101 along a first electron beam path 55 and/or along a second electron beam path 65. For that, the irradiation system 1 can comprise for instance adequate directing means, such as the ones shown in figures 1 -3 (see reference numbers 50 and 60), and/or one or more beam splitter(s). Hence, with this preferred embodiment, it is possible to produce both electron irradiation field 201 and X-ray irradiation field 202 with only one electron beam 101 produced by the radiation source 10. The other technical features described with reference to other preferred embodiments apply for the preferred embodiment shown in figure 6, mutatis mutandis. [0047] Depending on the size of the article 5 and on the size of the electron 201 and/or X-ray 202 irradiation field, only a portion of or the whole article 5 is irradiated during a treatment passing with the irradiation system 1 of the invention. If only a portion of an article 5 is irradiated during a treatment passing / treatment stage, it is preferable to impose different treatment stages to the article 5 in order to finally have an article 5 that has been fully irradiated. Therefore, the words Irradiation system 1 for irradiating an article 5' have to be understood as Irradiation system 1 for irradiating a whole article 5 or at least a portion of an article 5'.

[0048] Figures 7 shows a top view of a preferred conveyor band system 1 1 in combination with an irradiation chamber 30, shielding wall 20, technical room 90, electron irradiation horn 75 and X-ray irradiation horn 76. As shown in figure 7, conveyor band system 1 1 preferably comprises a single entrance conveyor 1 1 in for carrying the articles 5 into the irradiation chamber 30, both for the treatment by the electron irradiation field 201 and for the treatment by the X-ray irradiation field 202. Preferably, a single exit conveyor 1 l out allows carrying the articles 5 out of the irradiation chamber 30. Conveyor band system 1 1 preferably comprises a transport conveyor 1 1 t for passing the articles 5 under electron 75 and X-ray 76 irradiation horns along a treatment path 151 . This transport conveyor 1 1 t is preferably configured such that two articles 5 (boxes for instance) can be disposed at each side of each other. Electron irradiation horn 75 is preferably such that only one article 5 can be irradiated by the electron irradiation field 201 at a time. X-ray irradiation horn 76 is preferably such that two articles 5 can be irradiated by the X-rays irradiation field 202 at a time.

[0049] Conveyor band system 1 1 preferably comprises a reroute junction 12. This reroute junction 12 allows directing one or more articles 5 that have been irradiated either towards the exit conveyor 1 1 out, or again towards electron 75 and X-ray 76 irradiation horns, which means back towards electron irradiation field 201 and X-ray irradiation field 202. Therefore, the articles 5 can pass several times under electron 75 and X-ray 76 irradiation horns in this preferred embodiment, along a process loop 15.

[0050] According to another preferred embodiment (not shown here), the conveyor band system 1 1 comprises two different transport conveyors 1 1 t for passing the articles 5 through the electron irradiation field 201 and through the X-ray irradiation field 202.

[0051] The inventors propose the following method for efficiently irradiating an article 5 with an electron irradiation field 201 . In particular, this method allows obtaining a more uniform treatment of an article 5 that is irradiated by an electron irradiation field 201 . Figure 8 illustrates this method with a two-dimensional drawing (the horizontal arrows show the direction of the movement of the article 5 under the electron irradiation horn 75). The article 5 is irradiated with an electron irradiation field 201 during a first treatment passing. First treatment passing corresponds to left part of figure 8 with respect to the vertical line. The article 5 is positioned during said first treatment passing such that it presents in the irradiation chamber 30 a first boundary surface 5u upstream a second boundary surface 5b along said electron irradiation field 201 (in the two-dimensional drawing of figure 8, electron irradiation field 201 approximately reduces to a line). When the article 5 has a thickness along said electron irradiation field 201 that is larger than a threshold, only a portion of the article 5 can be efficiently irradiated by the electron irradiation field 201 . This is illustrated in figure 8 where the portion of the article 5 that is efficiently irradiated during first treatment passing is hatched. After this first treatment passing, the article 5 is rotated by 180° for inverting the positions of first 5u and second 5b boundary surfaces. Thereafter, a second treatment passing is imposed to the article 5 that has been rotated (right part of figure 8 with respect to vertical line). During this second treatment passing, first boundary surface 5u of the article 5 is positioned downstream second boundary surface 5b of same article 5 along the electron irradiation field 201 . This allows irradiating the portion of the article 5 that has not been treated during first treatment passing. Therefore, whole article 5 is hatched in right part of figure 8. This figure is academic for illustrating the method of the invention. Portion that is not hatched in left part of figure 8 does not represent a portion that has not been subjected to any electron irradiation field 201 . Such not hatched portion rather represents a portion that has not been irradiated by the electron irradiation field 201 with a sufficient uniform distribution. Hatched portions of figure 8 represent portions that have been uniformly (according to one skilled in the art's criteria) irradiated by the electron irradiation field 201 .

[0052] Preferably, the irradiation system 1 according to the invention comprises lifting means 85 for imposing a rotation of 180° of an article 5 between a first and a second treatment passing. Example of lifting means 85 is a mechanical system 85 that allows rotating an article 5. Such a mechanical system preferably 85 has a U-shape structure as it is shown in figure 9. Then, when the mechanical system 85 undergoes a 180° rotation, it exercises a 180° to the article 5 that is disposed in it. This allows inverting first 5u (or upper) and second 5b (or lower) boundary surfaces of an article 5. Preferably, lifting means or mechanical system 85 can impose a rotation of 180° to an article 5 by performing two successive rotations of 90°. The movement of rotation of the mechanical system 85 or lifting means is preferably imposed by a motor, for instance an electrical motor as it is known by the one skilled in the art.

[0053] More preferably, the mechanical system 85 comprises a first 17 and a second 18 lifting modules that are each capable of imposing a 90° rotation to an article 5. Such lifting modules (17; 18) are included in the top view of figure 7 and are shown in greater details in figure 10. As shown in this last figure, each lifting module (17; 18) preferably has an L-shape structure. First lifting module 17 is positioned upstream second lifting module 18 along the process loop 15. Hence, first lifting module 17 imposes a 90° rotation to an article 5 before second lifting module 18. The order of the operations follows the arrows of figure 10. First, the article 5 reaches first lifting module 17 with a first boundary surface 5u positioned above a second boundary surface 5b. Then, the article 5 is rotated by 90° due to the movement of rotation of first lifting module 17: first boundary surface 5u is then positioned right second boundary surface 5b. Thereafter, the article 5 reaches second lifting module 18 in same position as the one at the exit of first lifting module 17. Last, the article 5 is rotated by 90° due to the movement of rotation of second lifting module 18: first boundary surface 5u is then positioned under second boundary surface 5b. In this preferred embodiment, electron 201 and X-ray 202 irradiation fields are preferably directed vertically from up to down with respect to ground.

[0054] The inventors also propose a method for efficiently irradiating articles 5 with an X-ray irradiation field 202. Figure 1 1 illustrates a first example of such a method with two-dimensional drawings. In these drawings, the direction of the movement of the articles 5 under the X-ray irradiation horn 76 is illustrated by the circled dots, ie circles with a point inside them (hence movement of the articles 5 under the X-ray irradiation horn 76 is perpendicular to the plane of the two-dimensional drawings of figure 1 1 ). In figure 1 1 , four treatment passing or four treatment stages (401 , 402, 403, 404) are illustrated. However, only some of them could be used. In the example shown in figure 1 1 , the treatment stages are performed in the following order: 401 , 402, 403, 404. Different operations are carried out between these treatment stages as it is detailed below. For sake of clarity, neither the irradiation chamber 30 nor the shielding wall 20 are depicted in figure 1 1 ; however it has to understood that first 501 and second 502 articles are irradiated in said irradiation chamber 30 (that is shielded from the radiation means 10 thanks to the shielding wall 20) as it is clear from the above discussion related the irradiation system 1 of the invention.

[0055] The method illustrated in figure 1 1 allows irradiating a first 501 and a second 502 articles with an X-ray irradiation field 202 in a uniform manner. Hatched portions of the articles (501 , 502) represent portions that are treated at the end of each stage (401 , 402, 403, 404) in a uniform manner according to the one skilled in the art's criteria (same convention as the one used in figure 8).

[0056] During the treatment of first stage 401 , first 501 and second 502 articles are positioned next to each other. Conveyor band system 1 1 (not shown in figure 1 1 ) allows moving said first 501 and second 502 articles along a treatment path 151 in the irradiation chamber 30 under the X-ray irradiation horn 76 (seen figure 7). As first 501 and second 502 articles are positioned next to each other, it is possible to define a cross-section plane perpendicular to at least a portion of said treatment path 151 such that its intersection with first 501 and second 502 articles is non void. In the example shown in figure 1 1 , this cross-section plane is the plane of the two-dimensional drawings for instance. As shown in first stage 401 of figure 1 1 , first 501 and second 502 articles are also positioned such that first 501 (respectively second 502) article present in the irradiation chamber 30 a first boundary surface 501 u upstream a second boundary surface 501 b along the X-ray irradiation field 202. In the example shown in figure 1 1 , the X-ray irradiation field 202 is provided from above the articles (501 , 502): vertically and from up to down. Therefore, first boundary surface 501 u is positioned above second boundary surface 501 b in first stage 401 . At least a portion of each articles (501 , 502) is uniformly irradiated at the end of first stage 401 . Uniformly irradiated portions are depicted as hatched portions. They are defined by the distribution of penetration of X-rays and by the size of the irradiation field 202 at the level of the articles (501 , 502). After first stage 401 , articles (501 , 502) are inverted such that first article 501 takes the place of second article 502 and vice versa. New positions of the articles (501 , 502) are depicted in stage 402 of figure 1 1 . If one then irradiates the articles (501 , 502) with the X-ray irradiation field 202, additional portions of the articles (501 , 502) are uniformly treated as it is shown by hatched portions of both articles (501 , 502). After second stage 402, a rotation of 180° is applied to first and second articles (501 , 502) for inverting the positions of first (501 u, 502u) and second (501 b, 502b) boundary surfaces of first and second articles (501 , 502) along the X-ray irradiation field 202. In the example of figure 1 1 , this means positioning the first boundary surfaces (501 u, 502u) below the second boundary surfaces (501 b, 502b). Thanks to this new geometry, additional portions of first and second articles (501 , 502) can be irradiated uniformly and the end of third stage 403 as it is illustrated by new hatched portions of first and second articles (501 , 502). After third stage 403, first 501 and second 502 articles are inverted such that first article 501 takes the place of second article 502 and vice versa. By irradiating first 501 and second 502 articles with the X-ray irradiation field 202 in this new position, additional portions of the articles (501 , 502) can be uniformly irradiated after the fourth stage 404 or fourth treatment passing. Hence, treatment by X-rays is more efficient with this method as one can more fully and more uniformly irradiate the articles (501 , 502).

[0057] Figure 12 illustrates a second example of a method for efficiently treating articles 5 with an X-ray irradiation field 202. With respect to figure 1 1 , the differences are the followings. Between first 401 and second 402 stage, a rotation of 180° is applied to both articles (501 , 502) in order to invert positions of first (501 u, 502u) and second (501 b, 502b) boundary surfaces. Between second 402 and third 403 stage, positions of first 501 and second 502 articles are inverted. Between third 403 and fourth 404 stage, a rotation of 180° is applied to both articles (501 , 502) in order to invert positions of first (501 u, 502u) and second (501 b, 502b) boundary surfaces.

[0058] The two examples of method that are illustrated in figures 1 1 and 12 and that have been detailed above could also be used with an electron irradiation field 201 .

[0059] For imposing 180° rotations to first 501 and second 502 articles in order to invert the positions of their first (501 u, 502u) and second (501 b, 502b) boundary surfaces, the mechanical system 85 that is been described in relation to figures 9 and 10 is preferably used.

[0060] The present invention has been described in terms of specific embodiments, which are illustrative of the invention and not to be construed as limiting. More generally, it will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and/or described hereinabove. Reference numerals in the claims do not limit their protective scope. Use of the verbs "to comprise", "to include", "to be composed of", or any other variant, as well as their respective conjugations, does not exclude the presence of elements other than those stated. Use of the article "a", "an" or "the" preceding an element does not exclude the presence of a plurality of such elements.

[0061] The invention may also be described as follows. Irradiation system 1 for irradiating an article 5 with either an electron 201 or an X-ray 202 irradiation field and comprising: radiation means 10 for producing at least one electron beam, said irradiation system 1 being configured for directing a produced electron beam along a first electron beam path, and for directing a produced electron beam along a second electron beam path; an irradiation chamber 30 for receiving said article 5; a shielding wall 20 for shielding the irradiation chamber 30 from the radiation means 10. Said first 55 (respectively second 65) electron beam path is configured for delivering said electron irradiation field 201 (respectively said X-ray irradiation field 202) in said irradiation chamber 30 from an opening (21 ; 22) in said shielding wall 20.

Claims

1. Irradiation system (1 ) for irradiating an article (5) with an electron irradiation field (201 ) and/or an X-ray irradiation field (202) and comprising:

- radiation means (10) for producing at least one electron beam (101 ; 101 ,

102), said irradiation system (1 ) being configured:

• for directing an electron beam (101 ) produced by said radiation means (10) along a first electron beam path (55), and

• for directing an electron beam (101 ; 102) produced by said radiation means (10) along a second electron beam path (65);

- an electron irradiation horn (75) positioned at an end extremity of said first electron beam path (55) for forming said electron irradiation field (201 );

- an X-ray irradiation horn (76) positioned at an end extremity of said second electron beam path (65) for transforming an electron beam (101 ;102) produced by said radiation means (10) and following said second electron beam path (65) into said X-ray irradiation field (202);

- an irradiation chamber (30) for receiving said article (5) to be irradiated;

- a shielding wall (20) for shielding the irradiation chamber (30) from the radiation means (10);

- a conveyor band system (1 1 ) for carrying said article (5) from outside to inside said irradiation chamber (30);

characterized in that

- said first electron beam path (55) and said electron irradiation horn (75) are configured for delivering said electron irradiation field (201 ) in said irradiation chamber (30) from an opening (21 ; 22) in said shielding wall

(20); and in that

- said second electron beam path (65) and said X-ray irradiation horn (76) are configured for delivering said X-ray irradiation field (202) in said irradiation chamber (30) from an opening (21 ; 22) in said shielding wall (20);

such that said article (5) can be irradiated by said electron irradiation field (201 ) and/or by said X-ray irradiation field (202) in said irradiation chamber (30).

2. Irradiation system (1 ) according to claim 1 characterized in that it further comprises :

- first directing means (50) for directing an electron beam (101 ) produced by said radiation means (10) along said first electron beam path (55) towards said electron irradiation horn (75);

- second directing means (60) for directing an electron beam (101 ; 102) produced by said radiation means (10) along said second electron beam path (65) towards said X-ray irradiation horn (76).

3. Irradiation system (1 ) according to any of previous claims characterized in that said first electron beam path (55), said electron irradiation horn (75), said second electron beam path (65), and said X-ray irradiation horn (76) are configured such that said electron irradiation field (201 ) and said X-ray irradiation field (202) can be delivered in said single irradiation chamber (30) along two substantially parallel main directions (301 , 302).

4. Irradiation system (1 ) according to previous claim characterized in that said two substantially parallel main directions (301 , 302) are substantially perpendicular to a translation plane defined in said irradiation chamber (30) by said conveyor band system (1 1 ) and corresponding to a plane along which said conveyor band system (1 1 ) is able to carry said article (5) in said irradiation chamber (30) according to a translation motion.

5. Irradiation system (1 ) according to any of previous claims characterized in that said conveyor band system (1 1 ) comprises a single entrance conveyor (1 1 in) for carrying said article (5) from outside to inside said irradiation chamber (30).

6. Irradiation system (1 ) according to any of previous claims characterized in that :

- said conveyor band system (1 1 ) is also able to carry said article (5) from inside to outside said irradiation chamber (30), and in that

- said conveyor band system (1 1 ) comprises a single exit conveyor (1 1 out) for carrying said article (5) from inside to outside said irradiation chamber (30).

7. Irradiation system (1 ) according to any of previous claims characterized in that said conveyor band system (1 1 ) comprises a single transport conveyor (1 1 t) in said irradiation chamber (30) for moving said article (5) inside it.

8. Irradiation system (1 ) according to any of previous claims characterized in that said radiation means (10) is able to produce a first (101 ) and a second

(102) electron beams for respectively delivering said electron irradiation field (201 ) and said X-ray irradiation field (202), said irradiation system (1 ) being configured:

• for directing said first electron beam (101 ) along said first electron beam path (55), and

• for directing said second electron beam (102) along said second electron beam path (65).

9. Irradiation system (1 ) according to any of previous claims characterized in that said radiation means (10) is able to produce:

- an electron beam (101 ) whose electrons have a first mean energy, and

- an electron beam (101 ; 102) whose electrons have a second mean

energy,

said first and second mean energies being different.

10. Irradiation system (1 ) according to any of previous claims characterized in that said radiation means (10) is able to produce an electron beam (101 ) whose electrons have a mean energy comprised between 9 and 1 1 MeV.

11. Irradiation system (1 ) according to any of previous claims characterized in that said radiation means (10) is able to produce an electron beam (101 ; 102) whose electrons have a mean energy comprised between 6 and 8 MeV.

12. Irradiation system (1 ) according to any of previous claims characterized in that said radiation means (10) is able to produce an electron beam (101 ; 102) having a power comprised between 9 kW and 1 1 kW.

13. Irradiation system (1 ) according to any of previous claims characterized in that said radiation means (10) is able to produce an electron beam (101 ; 102) having a power comprised between 70 kW and 90 kW.

14. Irradiation system (1 ) according to any of previous claims characterized in that it further comprises an articles characterizing unit for determining at least one value related to the size and/or the density of said article (5).

15. Irradiation system (1 ) according to any of previous claims characterized in that it further comprises a control unit for imposing that said article (5) has to be irradiated by said X-ray irradiation field (202) when its size or its density is larger than a pre-determined value.

16. Irradiation system (1 ) according to any of previous claims characterized in that it further comprises a mechanical system (85) for imposing a rotation of 180° to said article (5) such that the positions of its upstream (5u) and downstream (5b) boundary surfaces along said electron (201 ) and X-ray (202) irradiation fields can be inverted.

17. Irradiation system (1 ) according to any of previous claims characterized in that it further comprises control means for inverting a first (501 ) and a second (502) articles such that said first article (501 ) can take the place of said second article (502) in said irradiation chamber (30) and vice versa.

18. Method for irradiating an article (5) with an electron irradiation field (201 ) of an irradiation system (1 ) according to any of previous claims, comprising the steps of:

- irradiating at least a portion of said article (5) with said electron irradiation field (201 ) during a first treatment passing, said article (5) being positioned during said first treatment passing such that it presents in the irradiation chamber (30) a first boundary surface (5u) upstream a second boundary surface (5b) along said electron irradiation field (201 );

- thereafter imposing a rotation of 180° of said article (5) for inverting the positions of said first (5u) and second (5b) boundary surfaces;

- thereafter irradiating at least a portion of said article (5) with said electron irradiation field (201 ) during a second treatment passing, said article (5) being positioned during said second treatment passing such that it presents in said irradiation chamber (30) said first boundary surface (5u) downstream said second boundary surface (5b) along said electron irradiation field (201 ).

19. Method for irradiating a first (501 ) and a second (502) articles with an X- ray irradiation field (202) of an irradiation system (1 ) according to any of claims 1 to 17, said irradiation system (1 ) comprising a conveyor band system (1 1 ) for moving said first (501 ) and a second (502) articles along a treatment path (151 ) in the irradiation chamber (30), said method comprising the steps of:

- positioning said first and second articles (501 , 502) next to each other such that it is possible to define a cross-section plane perpendicular to at least a portion of said treatment path (151 ) whose intersection with said first and second articles (501 , 502) is non void, said first and second articles (501 , 502) being also positioned such that they each present in said irradiation chamber (30) a first boundary surface (501 u, 502u) upstream a second boundary surface (501 b, 502b) along said X- ray irradiation field (202);

- thereafter, irradiating at least a portion of each of said first and second articles (501 , 502) with said X-ray irradiation field (202);

- thereafter, inverting said first and second articles (501 , 502) such that said first article (501 ) takes the place of said second article (502) and vice versa;

- thereafter, imposing a rotation of 180° to said first and second articles (501 , 502) for inverting the positions their first (501 u, 502u) and second (501 b, 502b) boundary surfaces; - thereafter, irradiating at least a portion of each of said first and second articles (501 , 502) with said X-ray irradiation field (202);

- thereafter, inverting said first and second articles (501 , 502) such that said that first article (501 ) takes the place of second article (502) and vice versa;

- thereafter, irradiating at least a portion of each of said first and second articles (501 , 502) with said X-ray irradiation field (202).

20. Method for irradiating a first (501 ) and a second (502) articles with an X- ray irradiation field (202) of an irradiation system (1 ) according to any of claims 1 to 17, said irradiation system (1 ) comprising a conveyor band system (1 1 ) for moving said first (501 ) and a second (502) articles along a treatment path (151 ) in the irradiation chamber (30), said method comprising the steps of:

- positioning said first and second articles (501 , 502) next to each other such that it is possible to define in said irradiation chamber (30) a cross- section plane perpendicular to at least a portion of said treatment path (151 ) whose intersection with said first and second articles (501 , 502) is non void in said irradiation chamber (30), said first and second articles (501 , 502) being also positioned such that they each present in said irradiation chamber (30) a first boundary surface (501 u, 502u) upstream a second boundary surface (501 b, 502b) along said X-ray irradiation field (202);

- thereafter, imposing a rotation of 180° to said first and second articles (501 , 502) for inverting the positions of their first (501 u, 502u) and second (501 b, 502b) boundary surfaces;