TECHNIQUES FOR HANDLING AND USING BA140 AS A TRACER

Abstract : Experiments on oxide-coated cathodes are described in which Ba 140 was used as a tracer. An oxide cathode of BaO containing Ba140 was used as an evaporator in a tube which contained several movable receivers on which the evaporated BaO was deposited. The activity of the receivers indicated the amount of Ba deposited. The time rate of deposition was previously verified as being constant at a given temperature (AD-13 839). The present tube design permits making the activity measurements through a thin glass bubble window in the side of the tube. This tube was used to measure the rate at which free Ba, produced at the cathode-base metal interface, diffuses to the surface and is evaporated to the anode. A technique of spraying radioactive BaCO3 was developed in order to produce cathodes of normal coating weight and density containing appreciable Ba140 (0.25mC/g). These cathodes were operated under quiescent conditions for various periods of time. This activity is related to the interface thickness, and its rate of formation could be determined as a function of life.