[en] GEANIE is a multi-detector, high-resolution gamma-ray spectrometer that is operated as a collaborative effort between Lawrence Livermore National Laboratory and Los Alamos National Laboratory. The WNR high-energy spallation neutron source at the Los Alamos Neutron Science Center (LANSCE) provides GEANIE's beam. GEANIE enables new measurements of neutron-induced reaction cross sections and fission fragment studies with neutrons with incident energies from 1 to 200 MeV and excellent γ-ray energy resolution. Results of first studies are aimed at providing information for such diverse areas as improved cross section data for stockpile stewardship needs and calibration of high-energy neutron fluence monitors for applications in Accelerator Production of Tritium and Accelerator Transmutation of Waste

[en] Excitation functions for proton elastic scattering and for proton induced reactions were measured with the KN Van de Graaff and associated high resolution system at TUNL for two odd-mass targets. Excitation functions for ²⁹Si(p,p), (p,p₁), and (p,p₂) were obtained in the range E/sub p/ = 1.29 to 3.30 MeV, and the ²⁷Al(p,p), (p,p₁), (p,p₂), (p,α₀), and (pα₁) differential cross sections were measured at four angles with an overall resolution that varied between 350 - 450 eV, full width at half maximum. The measured excitation functions were analyzed with a multi-level, multi-channel R-matrix formalism. The parameters extracted from the data include the resonance energy, total angular momentum, partial elastic and reaction widths, and channel spin and orbital angular momentum mixing ratios. Resonance parameters were determined for 66 resonances in ³⁰P in the range E/sub x/ = 6.85 to 8.79 MeV, and for 104 resonances in ²⁸Si in the range E/sub x/ = 12.47 to 14.53 MeV. The dependence of the resonance shapes on the channel spin mixing ratio and on the I-mixing ratio was investigated for proton scattering. Seven isobaric analog states were identified in ³⁰P and eighteen analog states were identified in ²⁸Si. Coulomb energies and proton spectroscopic factors were determined and the analog strengths compared with the parent state (d,p) spectroscopic factors

[en] GEANIE is a multidetector, high-resolution gamma-ray spectrometer that is operated as a collaborative effort between Lawrence Livermore National Laboratory and Los Alamos National Laboratory. The Weapons Neutron Research high-energy spallation neutron source at the Los Alamos Neutron Science Center provides GEANIE's beam. GEANIE enables new measurements of neutron-induced reaction cross sections and fission fragment studies with neutrons with incident energies from 1 to 200 MeV and excellent gamma-ray energy resolution. Results of first studies are designed to provide information for such diverse needs and calibration of high-energy neutron fluence monitors for applications in the accelerator production of tritium and accelerator transmutation of waste. Current efforts with GEANIE are focused on determining the ²³⁹Pu(n,2n)²³⁸Pu reaction cross section from threshold to 15 MeV from gamma-ray measurements. Because of the large fission-neutron background, this reaction is difficult to measure by neutron detection techniques. Only two direct measurements of this cross section as a function of neutron energy from threshold to higher energies have been reported, with large differences in the results. By measuring many partial gamma-ray cross sections in the decay cascade and modeling the reaction with a sophisticated preequilibrium-plus-Hauser-Feshbach computer program (GNASH), the author expects to achieve an absolute cross-section measurement of 10% accuracy or better. Key to current efforts has been the production of a very pure ²³⁹Pu sample with almost all ²⁴¹Am removed. As a test of their methods, and for other interests, he is measuring the ²³⁵U(n,nprimeγ) and (n,2nγ) cross sections and ²³⁸U(n,xnγ) reactions. The author is starting a program of fission fragment studies with French collaborators to look at spontaneous fission and neutron-induced fission

[en] Using the WNR white neutron source, photon production data have been acquired in the incident neutron energy range, 3 < E_n < 400 MeV, for a number of target nuclei using BGO detectors and high-resolution Ge detectors. The gamma-ray energy rang covered is 0.1 < E_γ < 10 MeV for the Ge detectors and 1.0 < E_γ < 20 MeV for the BGO detectors. The Ge detector measurements allow identification of reactions from the known energies of the gamma-ray transitions between low-lying states in the final nucleus. The lower resolution BGO data were also for discrete transitions. The data are useful both for testing nuclear reaction models at intermediate energies and for numerous applied purposes. We list the target nuclei studied to date and the status of the data

No abstract available

[en] Gamma-ray production cross sections and angular distributions were measured with five 7.6 cm diameter x 7.6 cm long BGO detectors at the high-energy white neutron source of the WNR facility at Los Alamos for targets of C ¹⁴NH₃ and ¹⁵NH₃. Gamma rays were measured in the energy range from 1.4 to 25 MeV. The incident neutron energies spanned the range from 2 to over 100 MeV. The detectors were positioned at angles of 39 degree, 55 degree, 90 degree, 125 degree, and 144 degree with respect to the neutron beam. We have extracted angular distributions and cross sections for the 4.44 and 15.1 MeV γ rays from inelastic excitation of C for 4 < E_n < 150 MeV. In ENDF-B/VI these γ-rays are treated as being isotropic. Our angular distributions show that this is not the case. For the nitrogen isotopes we have extracted angular distributions and cross sections for several γ rays in the neutron energy range, 2 < E_n < 20 MeV

[en] This document describes basic policies and provides information and examples on using the computing resources provided by P-17, the Neutron and Nuclear Science (NNS) group. Information on user accounts, getting help, network access, electronic mail, disk drives, tape drives, printers, batch processing software, XSYS hints, PC networking hints, and Mac networking hints is given

[en] Measurements of prompt gamma rays following neutron-induced reactions have recently been made at the spallation neutron source at the WNR target area of LAMPF using germanium detectors. These experiments provide extensive excitation function data for inelastic neutron scattering as well as for other reactions such as (n,α), (n,nα), (n,p), (n,np), (n,nnp) and (n,xn) for 1 ≤ x ≤ 11. The continuous energy coverage available from 1 MeV to over 200 MeV is ideal for excitation function measurements and greatly extends the energy range for such data. The results of these measurements will provide a database for interpretation of gamma-ray spectra from the planned Mars Observer mission, aid in radiation transport calculations, allow verification of nuclear reaction models, and improve the evaluated neutron reaction data base

[en] This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The goal of this project was to explore an upgrade to the GEANIE high-resolution gamma-ray spectrometer at the Los Alamos Neutron Science Center (LANSCE) to help build additional experimental capabilities. The improvements identified have significantly added to the capabilities of GEANIE and made the facility more attractive for studies supporting the core national security mission as well as for use by outside collaborators. These benefits apply to both basic and applied studies

[en] The continuous energy (white) neutron source at the Los Alamos Meson Physics Facility (LAMPF) is used to measure photon-production cross sections over a wide range of neutron energies. Detector systems have been or are being developed to measure gamma rays in the energy range from hundreds of keV up to several hundreds of MeV. In particular a high resolution Ge detector system is used to detect gamma rays from several hundred keV to over 6 MeV. A 5 crystal BGO detector system is used for measuring gamma-rays from 1 MeV to approximately 20 MeV. A large volume BGO detector with an active shield is used to measure gamma rays in the range from 5 to 40 MeV. We are presently developing a multi-element gamma-ray telescope to measure gamma rays with energies from 50 MeV up to several hundred MeV