Production, chemical and isotopic separations of the long-lived isomer¹⁷⁸Hf^m2(T_1/2=31 years)

Abstract

A b s h d . ?%e nucleus '"Hf, with its long-lived (T,n = 31 y) high-spin isomeric state i"= 16'. is a chaiienge for new and exotic nuciear physics studies. w e describe the first experiments we have performed in order to produce a reasonable microweight quantity of this hafnium isomer with an isomeric to ground-state ratio as high as possible (here 5%). The reaction '"Yb (4He,2n) using an enriched target has been studied by measuring the excitation functions and the isomeric to ground-state ratio. About 3 X 10' ' isomeric atoms have been produced up to now in irradiations with high-intensity beams (-100pA) at the U-200 cyclotron in Dubna. Chemical separation methods could be checked using about 10'" atoms of the isomer. Isotopic separation experiments have been performed in Orsay and preliminary results are given for the separation efficiency.

Production of long-lived hafnium isomers in reactor irradiations

“…Definitely, the high yield characterizing spallation reactions was confirmed and quantitatively specified. The 176 Yb( 4 He, 2n) reaction at 36 MeV He-ion beam seemed attractive in another aspect, namely in the sense of the best purity of the produced 178m 2 Hf activity [23], as compared to the spallation and other reactions. Recently, a productivity of high-energy bremsstrahlung for the 178m 2 Hff accumulation has been tested [24] using the Ta sample irradiated with electrons at 5 GeV synchrotron.…”

Nuclear structure and the search for induced energy release from isomers

“…Not naturally-occurring, samples containing 178m2 Hf trace their lineage to two productions, by fusion evaporation [17] and proton spallation [18]. The former material is of far greater purity (about 5% isomer-toground-state ratio), but in lesser quantity.…”

Radionuclide Generators

“…The excitation function for the 124 Xe(p,x) 122 Xe process demonstrated that it is a feasible route for production of the 122 Xe -• ,22 I generator [111]. The thick target yield of 122 Xe was reported as 13.5 mCi/μΑΙι over the optimum energy range of E P = 43-35 MeV.…”

“…The thick target yield of 122 Xe was reported as 13.5 mCi/μΑΙι over the optimum energy range of E P = 43-35 MeV. See References [1,2] for further details on Xe -• I generators.…”

“…The 172 Hf can be produced by 800 MeV proton irradiation [120,121], isotope separations [122] or by 45 MeV 4 He bombardment of na, Yb [123]. Das et al [123] recently described the performance of a new generator system.…”