Charged particles produced in neutron reactions on nuclei from beryllium to gold

Charged-particle production in reactions of neutrons with nuclei has been studied over the past several years with the spallation source of neutrons from 1 to 50 MeV at the Los Alamos Neutron Science Center (LANSCE). Target nuclides include 9Be, C, 27Al, Si, 56Fe, 59Co, 58,60Ni, 93Nb and 197Au. Proton, deuteron, triton, 3He and 4He emission spectra, angular distributions and production cross sections have been measured. Transitions from the compound nuclear reaction mechanism to precompound reactions are clearly seen in the data. The data are compared with data from the literature where available, with evaluated nuclear data libraries, and with calculations where the selection of the nuclear level density prescription is of great importance. Calculations normalized at En = 14 MeV can differ from the present data by a factor of 2 for neutron energies between 5 and 10 MeV

NASA Data Archive Evaluation

The purpose of this study was to expose a range of naive individuals to the NASA Data Archive and to obtain feedback from them, with the goal of learning how useful people with varied backgrounds would find the Archive for research and other purposes. We processed 36 subjects in four experimental categories, designated in this report as C+R+, C+R-, C-R+ and C-R-, for computer experienced researchers, computer experienced non-researchers, non-computer experienced researchers, and non-computer experienced non-researchers, respectively. This report includes an assessment of general patterns of subject responses to the various aspects of the NASA Data Archive. Some of the aspects examined were interface-oriented, addressing such issues as whether the subject was able to locate information, figure out how to perform desired information retrieval tasks, etc. Other aspects were content-related. In doing these assessments, answers given to different questions were sometimes combined. This practice reflects the tendency of the subjects to provide answers expressing their experiences across question boundaries. Patterns of response are cross-examined by subject category in order to bring out deeper understandings of why subjects reacted the way they did to the archive. After the general assessment, there will be a more extensive summary of the replies received from the test subjects

Nuclear-data needs for inertial-confinement fusion (ICF)

Our survey was limited to ICF programs in the United States. It included researchers in laser and heavy ion fusion, target design, target diagnostics, and conceptual reactor design. We asked each of these people to read the current data needs for magnetic fusion energy and to comment on additional data that they require

Status report to DOE Nuclear Data Committee

This status report from Lawrence Livermore Laboratory covers work in the areas of nuclear data applications - measurements, nuclear data application - calculations, nuclear data for reactor safety, fission physics, and data evaluation and compilation. Separate abstracts were prepared for seven of the contributions to this report. 7 figures, 3 tables. (RWR

Experimental studies of (n, charged particle) cross sections, angular distributions and spectra with a magnetic quadrupole spectrometer

The charged-particle-producing reactions of 15-MeV neutrons with structural materials have been studied with a new type of spectrometer based around a magnetic quadrupole lens. Significant improvements in signal-to-background have permitted the detection of protons with energies as low as 800 keV. In several materials charged particles emitted with energies well below the Coulomb barrier contribute significantly to the total hydrogen and helium production cross sections. The production mechanism for these low-energy particles is second-chance emission in (n,n'p) and (n,n'..cap alpha..) reactions. At the high-energy end of the proton and alpha-particle spectra and for the entire deuteron spectra, non-statistical reaction mechanisms are indicated. Results for Al, Ti, V, Fe, Ni, Cu, Nb, and stainless steel 316 are compared with data from other experimental methods

The 14C(n,g) cross section between 10 keV and 1 MeV

The neutron capture cross section of 14C is of relevance for several nucleosynthesis scenarios such as inhomogeneous Big Bang models, neutron induced CNO cycles, and neutrino driven wind models for the r process. The 14C(n,g) reaction is also important for the validation of the Coulomb dissociation method, where the (n,g) cross section can be indirectly obtained via the time-reversed process. So far, the example of 14C is the only case with neutrons where both, direct measurement and indirect Coulomb dissociation, have been applied. Unfortunately, the interpretation is obscured by discrepancies between several experiments and theory. Therefore, we report on new direct measurements of the 14C(n,g) reaction with neutron energies ranging from 20 to 800 keV