Patent Number: 
Section: claims

1. A method for irradiating in an irradiation chamber products being stored in the form of pallets or in the form of bulk material in containers with a high energy x-ray beam source, the method comprising:placing the products onto two different levels of products, so that a first set of products is placed on an upper level and a second set of products is placed on a lower level;irradiating both sets of products during a first period of time by directing the x-ray beam source to the products from about mid-height of the products on the lower level to about mid-height of the products on the upper level;switching the products placed on the two levels to make a new arrangement so that the set of products irradiated on the upper level during the first time period are placed on the lower level and the set of products irradiated on the lower level during the first time period are placed on the upper level; andirradiating during a second period of time the new arrangement formed of the two switched sets of products by directing the x-ray beam source to the products from about mid-height of the products on the lower level to about mid-height of the products on the upper level. 2. The method according to claim 1, wherein the two different levels are two superposed vertical levels. 3. The method according to claim 1 wherein the total period of irradiation comprises the first period of time and the second period of time and the switching of the two levels occurs in the middle of the total period of irradiation of the products. 4. The method according to claim 1, wherein the products are conveyed before the source with a translation conveyor device. 5. The method according to claim 4, wherein the translation conveyor device comprises two independent parallel sub-devices conveying the products on the two different levels. 6. The method according to claim 1, wherein the products are conveyed before the source with a rotating conveyor device. 7. The method according to claim 6, wherein the rotating conveyor device comprises two independent parallel sub-devices conveying the products on the two different levels. 8. The method according to claim 1, wherein the set of products present on each level comprises one pallet or one container. 9. The method according to claim 1, wherein the set of products present on each level is in the form of a stack of at least several contiguous pallets or containers placed in the same plane. 10. The method according to claim 9, wherein the plane is essentially a horizontal plane. 11. The method according to claim 1, wherein the high energy x-rays are obtained by scanning an electron beam along a conversion target on a height essentially corresponding to a distance comprised between substantially mid-height of the lower level up to substantially mid-height of the upper level. 12. An apparatus for irradiating in an irradiation chamber products being stored in the form of pallets or in the form of bulk material in containers, the apparatus comprising:a high energy photon source;a conveying device configured to convey the products in front of the photon source and arrange the products in two sets of products, each being placed on a different level, the different levels comprising an upper level and a lower level;a transposition device configured to switch the sets of products arranged on each level so that the set of products irradiated on the upper level during the first time period are placed on the lower level and the set of products irradiated on the lower level during the first time period are placed on the upper level, anda directing device configured to direct the high energy photon source to the products from about mid-height of the products on the lower level to about mid-height of the products on the upper level. 13. The apparatus according to claim 12, further comprising a directing device configured to direct a photon beam along a height essentially corresponding to a distance comprised between substantially mid-height of the lower level products up to substantially mid-height of the upper level products. 14. A method for irradiating in an irradiation chamber products being stored in the form of pallets or in the form of bulk material in containers with a high energy x-ray beam source, the method comprising:placing the products onto two different levels of products so that a first set of products is placed on an upper level on a first horizontal plane and a second set of products is placed on a lower level on a second horizontal plane;irradiating both sets of products during a first period of time by directing the x-ray beam source to the products from about mid-height of the products on the lower level to about mid-height of the products on the upper level and holding the first and second horizontal planes stationary during the first time period;switching the products arranged on the two levels to make a new arrangement so that the set of products irradiated on the upper level during the first time period are placed on the lower level on the second horizontal plane and the set of products irradiated on the lower level during the first time period are placed on the upper level on the first horizontal plane; andirradiating during a second period of time the new arrangement formed of the two switched sets of products by directing the x-ray beam source to the products from about mid-height of the products on the lower level to about mid-height of the products on the upper level and the first and second horizontal planes are held stationary during the second time period,wherein the total period of irradiation comprises the first period of time and the second period of time and provides a dose uniformity ratio less than 2.5. 15. The method according to claim 14, wherein the two different levels are two superposed vertical levels. 16. The method according to claim 14, wherein the switching of the two levels occurs in the middle of the total period of irradiation of the products. 17. The method according to claim 14, wherein the products are conveyed before the source with a translation conveyor device comprising two independent parallel sub-devices conveying the products on the two different levels. 18. The method according to claim 14, wherein the products are conveyed before the source with a rotating conveyor device comprising two independent parallel sub-devices conveying the products on the two different levels. 19. The method according to claim 14, wherein the dose uniformity ratio is about 1. 20. The method according to claim 14, wherein the high energy x-rays are obtained by scanning an electron beam along a conversion target on a height essentially corresponding to a distance comprised between substantially mid-height of the lower level up to substantially mid-height of the upper level.