Détermination du débit optimum pour la production par cyclotron de gaz radioactifs à partir de cibles gazeuses

When short-lived radioactive gases are produced by cyclotron-irradiated gaeous targets, the yield of activity at the site of delivery depends on the flow rate in the gas carrying line. The authors present a single model which allows to compute the flow rate D giving a maxmim yield of production. The following formula is used : D= 1/2 [ λ(2)Vπ(2) + √λ(2) V(2) + 4 λ VπVc] where λ is the decay constant of the produced radionucide, Vc the volume of gas in the target, and Vπ the inner volume of the gas carrying line. The only unknown parameter Vπ can be derived from a single curve of growing of the activity at a trial flow rate. The method is concretely applied to the production of 15-oxygen, 13-nitrogen and 11-carbon.