Yield of radionuclides and isomers produced in the fragmentation of natW and 186W (97%) targets with protons at 630, 420 and 270MeV

Induced decay of a long-lived nuclear isomerHf178m2in a laser thermonuclear plasma

“…The reaction mechanism was a 800-MeV proton spallation on a Ta target. According to measurements [14] 178 Hf m2 isomeric nuclei and 178 Hf nuclei in the ground state appear in this reaction at a ratio close to 1/50.…”

“…According to data [14] the isomer-to-groundstate ratios σ m /σ g are 0.092 and 0.14 for the 186 W target and for the natural Re target, correspondingly. The small admixture of other hafnium isotopes can be removed by standard method of isotopes separation.…”

Spallation and fission products in the (p+179Hf) and (p+natHf) reactions

“…In our previous experiments [1,2] on the spallation of Ta to Re targets, metal samples were irradiated. Even enriched 186 W material was available [2] in a metal form and in enough amount.…”

“…In Refs. [1,2], the yields of high-spin isomers were measured in the spallation of the Ta to Re targets exposed to protons with energy range from 100 to 650 MeV. The enriched 186 W target was indicated as one of the most productive targets for accumulation of the 31-year-lived 178m2 Hf isomeric state located at excitation energy of E i = 2446 keV and at spin I π = 16 + .…”

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

“…Second, the more productive nuclear reaction is chosen, the longer (in most cases from 6 to 20 years) cooling time for the by-products activity reduction is required. 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].…”