Production of the 178m2Hf isomer using a 4.5-GeV electron accelerator

High-productivity methods are required for the accumulation of long-lived isomers in amounts that are sufficient for the creation of experimental targets. A tantalum sample was activated with the Yerevan synchrotron using 4.5-GeV bremsstrahlung and the presence of 178m2Hf was detected with good statistical accuracy by γ-activity measurements. The integrated and mean cross-section values were deduced from the experiment. The isomer-to-ground-state ratio was then estimated and compared with that known for the p+ Ta reaction studied at 660 MeV. In the present experiment, both converter and target were relatively thin for better definition of the experimental conditions. However, an assembly designed for high-productivity irradiations should be thick and then the converter can also serve as the target sample when irradiated with a high-energy electron beam. The optimization of the isomer production was solved analytically and the largest estimated yield was determined as calibrated to the experimental yield. The maximum yield of 178m2Hf was found to be of about 3×109 nuclei/s using an electron beam current of 100 μA. This is lower than the yield achieved with proton beams, although for a practical comparison the total cost and radiation safety conditions should be considered. The present results provide a basis for numerical estimations.