A cobalt machine for semi-acute irradiation of growing plants

Abstract A Co 60 machine for irradiating growing plants with gamma rays is described. The 200 c machine is shielded behind earthen bunkers with concrete retaining walls, also a sky-shine shield intercepts vertical radiation. The radiation at the control house, 100 ft away, receives 2 mr/hr. The source is held in place by an electromagnet which is raised and lowered by a windlass in the control house by means of a stainless-steel cable. In case of power failure the Co 60 source drops into the lead container in the center of the field. Either seeds, plants or other biological specimens may be treated. Doses ranging from 7000 r/hr at 20 cm to 1 r/hr at 20 m may be used. At 1 m the dose is 310 r/hr or approximately 7300 r for a 23 1 2 hr day. A dose of 1000 r is sufficient for inducing many mutations in plant material. This can be obtained in 23 1 2 hr at about 3 m from the source.