Production of the^178m2Hf isomer using a 1.2 GeV electron accelerator

Abstract

We analyzed possibilities for the production of 178m2Hf isomers in amounts necessary for the preparation of experimental targets. In our case the 178m2Hf isomers were produced during irradiation of the Ta converter by 1.2 GeV electrons at the Kharkiv linear accelerator many years ago. At such high electron energies the concurrent nuclear reactions are very numerous and, though all short-lived nuclei decay completely, the target is contaminated by the significant amount of long-lived nuclides. This allowed us to study the production of not only the 178m2Hf isomer, but also those of 60Co, 101Rh, 102mRh, 108mAg, 133Ba, 150Eu, 152Eu, 154Eu, 158Tb, 173Lu, 174Lu, 172Hf and 179Ta. The production yields and cross-sections for corresponding photonuclear reactions were estimated and compared with the results of other authors and calculations with the aid of the Rudstam formula.

Observation of enhanced activity of the 178m2Hf isomeric target after its irradiation by bremsstrahlung radiation

“…In addition to a very low activity (∼100 Bq), our isomeric target has another feature -along with other longlived nuclides, it contains significant amounts of 133 Ba and 150 Eu [29]. The total intensity of the (γ356 + γ303 keV) 133 Ba and (γ334 + γ439 keV) 150 Eu peaks in the spectrum of the isomeric target approximately corresponds to the intensity of the γ426 keV peak of the 178m2 Hf isomer.…”

Induced acceleration of the decay of the 31-yr isomer of 178m2 Hf using bremsstrahlung radiation

“…Such situation forced the intense search for any Ta targets irradiated by high-energy projectiles many years ago [16]. As a result, Ta foil of 300 μm thickness with about 100 Bq 178m2 Hf isomer activity that in 1967-1970 had been exploited as the converter at the Kharkiv 1.2 GeV Linac was found [17]. The objective of this work is to check much more carefully which transitions observed in the spontaneous decay of the 178m2 Hf isomer can really be enhanced.…”