No abstract

Excited states in 208 Pb have been studied by measuring ␥ rays in time coincidence with reaction charged particles. 208 Pb states were produced with both the 207 Pb(d, p) 208 Pb and 209 Bi(t,␣) 208 Pb reactions. The energy resolution of the particle spectra of 100 keV allowed a rough determination of level excitation, which then was determined with high resolution from the coincident ␥ decay measured in Ge detectors. Many new ␥ transitions have been found and previously unresolved multiplets of states resolved. The data give spectroscopic factors for neutron transfer and proton pickup. Spins and parities of levels could be deduced from their ␥ decays. A least squares fit of all ␥ energies gave very precise ͑0.1 keV͒ level energies. All states predicted by the shell model below 4.6 MeV are now found and their spins determined unambiguously. ͓S0556-2813͑97͒03009-4͔PACS number͑s͒: 21.60. Cs, 23.20.Lv, 25.45.Hi, 27.80.ϩw II. THE 209 Bi"t,␣␥… 208 Pb EXPERIMENT A. Design of the experiment and proceduresThe 209 Bi(t,␣␥) 208 Pb reaction was used to excite levels in 208 Pb. Due to the huge positive energy balance of this

No abstract

No abstract

Abstract-Several active interrogation techniques are being developed to detect shielded special nuclear materials (SNM) hidden in cargo containers loaded on container ships arriving at US ports. It raises the questions of the types of cargos in which SNM could be hidden, and their impact on detected signatures. Since the definition of a set of "typical" or standard cargos has proven to be difficult, we analyzed shipping manifests for US imports shipped through North American ports collected on 14 days distributed over 12 months. From these data, we generated several distribution functions such as commodity categories, average densities, and packaging types that could be of interest to the cargo scanning community.One of the cargo scanning techniques currently under development at LLNL is based on neutron active interrogation, and relies on the unique signature of beta-delayed gammas emitted by fission products in the 3 to 7 MeV energy range. 19 F(n,a) 16 N, has been identified as the main potential interference for 7 and 9 MeV neutron beams. Estimates of cargo compositions based on manifests identified as containing fluorine are presented.