Abstract: An accelerator (10) generates an electron beam that is swept (16) up and down to form an electron beam (22). A conveyor (32) moves items (30) through the electron beam for irradiation treatment. A first array of inductive electron beam strength detectors' (40a) is disposed between the origin of the electron beam and a first item to be irradiated to measure the strength of the electron beam entering the item at a plurality of altitudes. A second array (42) of inductive electron beam strength detectors is disposed on the opposite side of the item to detect the strength of the electron beam exiting the item at the plurality of altitudes. In the illustrated embodiment, another item is positioned to be irradiated by the radiation that is passed through the first item. The second array thus detects the electron beam strength entering the second item and an analogous array (40c) measures the electron beam strength exiting the second item.