THE NEW AEA EB PLANT AT HARWELL

A new electron beam irradiation plant is at present being commissioned at AEA Technology's Harwell site. The principal components of the pla nt are a single-section travelling wave L-band linac, an energy analys is and beam scanning system, a product conveyor system and a large war ehouse. The design of the new linac is based on the first section of t he Harwell electron linear accelerator HELIOS originally used for nucl ear research The beam transport system on the new linac incorporates e nergy analysis, beam focussing and a dual magnet scanning system which ensures that the electron beam is always normal to the surface of the product under irradiation as it passes directly beneath the beam exit window. The product conveyor system is based on an inverted ''power & free'' chain conveyor. The speed of the section of conveyor beneath t he scanned beam is servo-controlled by the linac output, which is meas ured with a non-intercepting toroidal beam monitor. Dosimetry is based on Far West film for product validation, Harwell 4034 red perspex for routine dosimetry and Riso polystyrene calorimeters for direct electr on beam monitoring. The design and first stages of plant commissioning are described.