PRODUCTION OF [N-13] AMMONIA APPLICABLE TO LOW-ENERGY ACCELERATORS

We have developed a technique for the rapid conversion of the nitrogen -13 induced in a graphite target into nitrogen oxides. This was accomp lished by heating the graphite target in a stream of pure oxygen at 80 0 degrees C. Less than 20% of the radioactivity was found in the form of [N-13]nitrogen. The rest of the radioactivity was efficiently trapp ed in a solid-phase medium that consisted of an aqueous solution of 5% NaOH dispersed in silica gel. The radioactivity from this solid-phase medium was eluted with water (94% recovery) and found to be in the fo rm of (NO2-)-N-13 (99%). This was subsequently converted to [N-13]ammo nia with Raney-nickel, either by a conventional liquid-phase reduction with an overall conversion efficiency to ammonia of 45%, or by an inc orporation of the Raney-nickel into the solid-phase medium. The latter system resulted in an overall conversion efficiency to ammonia of 37 +/- 9%, with a radiochemical purity of nearly 100% and a synthesis tim e under 17 min.