Patent Number: 
Section: abstract

An accelerator (10) generates an electron beam (22) of selected energy that is swept (16) up and down. A conveyor (32) moves items (30) through the electron beam for irradiation treatment. An array (40a) of inductive electron beam strength detectors is disposed on a down stream side of the item to detect the energy of the electron beam exiting the item at the plurality of altitudes. The electron beam strength entering and leaving the item are communicated to a processor (54) which determines the absorbed dose of radiation absorbed by the item. The dose information is archived (56) or compared by a parameter adjustment processor (58) with target doses and deviations are used to control one or more of MeV or beam current of the electron beam, the sweep rate, and the conveying speed of the items. Each of the detectors includes a vacuum chamber in which two current transformers (60, 62) disposed on either side of a metal foil layer (64). From the difference in the current induced in the two transformers by a pulsed, collimated electron beam, the energy of the beam is determined.