[en] The post-fusion emission from the ¹⁶O + ¹²C reaction, which results in a distribution of residual nuclei, was measured in a series of experiments. The multiplicity and energy spectra of the charged-particle, neutron, and γ-ray emission associated with each major residue were determined for seven ¹⁶O beam energies from 43.2 MeV to 60.7 MeV. For each of the major residues, the energy of the measured emissions accounted for the initial excitation energy. Comparisons with statistical model calculations were made using the computer codes LILITA and CASCADE. Both codes are based on the Hauser-Feshbach formalism describing the formation and decay of the compound system. Although the qualitative agreement between the theoretical predictions and the experimental data was good, the quantitative agreement was, in general, poor. The entry region was determined for each residue and, except for the ²⁶Al residual nucleus, was found to be consistent with the particle decay occurring mainly to low-lying discrete states. The entry region for the ²⁶Al residue was found to parallel the yrast line (i.e., the slope was the same) but was about 2 and 3 MeV of excitation energy above it

[en] A method is described for determining the strength of the complex central optical potential directly from neutron total cross sections measured below the threshold for inelastic scattering. Real and imaginary strengths deduced for ²⁰⁸Pb are consistent with higher-energy results and are shown to provide a good fit to above-threshold data. (orig.)

[en] Excitation functions for the yields of nineteen residual nuclei from the ¹⁴N+¹⁰B reaction have been measured over the range E/sub c.m./ = 8.00--25.75 MeV in steps of 250 keV with γ-ray techniques. The magnitude and energy dependence of the excitation functions for the partial yields are very different from those of the ¹²C+¹²C system. The total fusion cross section appears to saturate at an energy and a magnitude which are lower than expected from previous systematics. Small, regular fluctuations can be seen in the fusion cross section, one of which is very narrow. However, the structure observed by L'Ecuyer et al. was not seen in this work

[en] High-enriched uranium (HEU) emits sufficient thermal power and gamma rays that a combination of calorimetric assay and gamma-ray spectroscopy can be used for the determination of ²³⁵U content. The thermal power is primarily generated by the ²³⁴U fraction that is enriched along with the ²³⁵U during isotopic separation processes. HEU with an enrichment of 93% ²³⁵U contains about 1% ²³⁴U and the resultant specific power is 2 milliwatts/kilogram. This is sufficient power for assay by high sensitivity calorimeters of quantities of HEU metal, high-grade scrap, feed and process materials. The calorimetric measurements are used in conjunction with measurements by high-resolution germanium detectors of the relative gamma-ray intensities of ²³⁴U and ²³⁵U. The ²³⁴U/²³⁵U ratio is determined using the 121 keV ²³⁴U and 144 keV ²³⁵U gamma rays. The measured intensities of ²³⁵U gamma rays (144--200 keV) are used to estimate the relative efficiency of detection for the two gamma peaks. The isotopic ratio is calculated using the measurement data and the known ²³⁴U and ²³⁵U branching ratios and half-lifes. The ²³⁵U content of a container can be determined from the ²³⁴U/²³⁵U isotopic ratio and the quantity of ²³⁴U as determined by calorimetry. The calorimetric/gamma-ray technique requires no physical standards and could be used for verification measurements or for the characterization of physical standards. The results of measurements performed on HEU samples will be reported

[en] Calorimetric assay, the combination of calorimetry and gamma ray spectrometry, plays a vital role in the material control and accountability systems of the United States Department of Energy. Several recent advances in calorimetry have improved the precision, reduced the measurement time and increased the portability of the systems, and have made them more user friendly. Calorimeter systems have been configured as rugged transportable systems in support of nuclear material accountability inspectors. These systems can be transported easily by an inspection team and set up rapidly at a site. A complete verification system may include a transportable calorimeter, a gamma ray isotopic system and a passive neutron correlation counter. This combination of instruments provides the ability to evaluate non-destructively a wide variety of materials without the use of physical standards or a 'wet' chemistry laboratory, thus providing a more independent verification of nuclear material inventory. (author). 4 refs, 3 figs, 1 tab

[en] Excitation functions for the yields of eleven residual nuclei from the ¹⁴N+¹⁴N reaction have been measured over the range E_c.m. = 7--25 MeV in steps of approx.250 keV with γ-ray techniques. The magnitude and energy dependence of the excitation functions for the partial yields are very different from those for the ¹²C+¹⁶O system. The total fusion cross section is similar to that from ¹²C+¹⁶O when compared at the same center of mass energy, but appears to saturate at an energy and magnitude which are lower than expected from previous systematics. Small, regular fluctuations can be seen in the fusion cross section at the 1--2 % level

[en] Excitation functions for the yields of ten residual nuclides from the ₁₂C+₁₂C reaction have been measured over the range E_c.m. = 5.25--20.0 MeV in steps of 125 keV, using ν-ray techniques. Nearly all of the reaction channels, including those with light-particle evaporation, showed strong narrow structures. A qualitative statistical analysis performed on the data gave useful information about the locations of possible nonstatistical structure, based primarily on the very strong cross-channel correlation observed in the data set

[en] Excitation functions for the yields of eight residual nuclides from the ¹⁶O+²⁰Ne reaction have been measured over the range E_c.m = 25--29 MeV using γ-ray techniques. Weak oscillatory structure in the fusion-evaporation yield is observed, with maxima near E_c.m. = 20, 22, and 23 MeV. Two strong anomalies in the inelastic scattering and α-transfer channels have been located at E_c.m. = 19.9 and 25.4 MeV. These structures have properties similar to those of characteristic resonances in other light systems. The E_c.m. = 19.9 MeV resonance occurs at the same ³⁶Ar excitation energy as a similar resonance previously observed in the ¹²C+²⁴Mg reaction yields

[en] A new T = 0 level of ¹⁸F, Esub(x) = 4848.3 +- 0.5 keV, has been studied using the ⁶Li(¹⁶O,αγ)¹⁸F reaction. The γ-decay by a 65 +- 4% branch to the 1121 keV (5⁺) level and 35 +- 4% to the 3791 keV (3^-) level has been observed and a lifetime limit tau > 2 ps has been given. A tentative assignment Jsup(π) = 5^- is proposed which is supported by the α-γ angular correlation measurements. The possible structure of the new level and reasons why it had not been observed in past experiments are discussed. (orig.)