Showing papers by "Klaus H Guber published in 2006"

R-matrix analysis of Cl neutron cross sections up to 1.2 MeV

Abstract: We have analyzed and evaluated {sup 35}Cl, {sup 37}Cl, and {sup nat}Cl neutron cross section data in the resolved resonance region with the multilevel Reich-Moore R-matrix formalism. Energies and widths were determined for 388 resonances in the range 0.2 to 1200 keV. New J assignments were made for 33 resonances, and parities were assigned for 15 of these resonances. Neutron strength functions were calculated for both s and p waves; our results include the first reported p-wave values for Cl. Resonance analyses were carried out with the computer code SAMMY, which utilizes Bayes' method, a generalized least-squares technique. Because SAMMY now has the ability to calculate charged-particle penetrabilities, it was possible to include a proton exit channel in the analysis and to deduce proton widths for several resonances. Our resonance parameter representation describes the data much better than previous evaluations, and it should lead to improved criticality safety calculations for systems where Cl is present.

Recent operation of the orela electron linac at ornl for neutron cross section research

Abstract: The ORNL electron LINAC, ORELA, began operation in 1969 and has been instrumental in providing improved neutron cross section data for many isotopes over the 0.002-60 MeV energy range. The ORELA utilizes a 2-30 ns <1000 Hz pulsed gridded electron gun, a 4 section RF LINAC, and a water-cooled and moderated tantalum target to generate short neutron pulses. The short pulse lengths and long flight paths provide high neutron energy resolution. Beam energy can range up to 180 MeV and a neutron production rate of up to 10 14 n/sec can be generated with 50 kW of beam power. Recent operation is at 8 ns, 525 Hz pulse rate and a target power of 5-10 kW. RF power for the accelerator sections are provided by four 24 MW 1300 MHz klystrons. Recent activities have included improvements to the accelerator vacuum, klystrons, interlocks and other upgrades. The current ORELA program is focused on cross-section measurements for the Nuclear Criticality Safety Program and for nuclear astrophysics. Detection and data analysis capabilities have been developed for making highly accurate measurements of neutron capture, neutron total, (n, ), and (n,fission) cross-sections simultaneously on different beam lines.