R. O. Sayer

Validity of collective model DWBA analysis for intermediate energy proton scattering to low-lying states of 208Pb

Abstract New measurements of inelastic proton scattering to low-lying collective states of 208 Pb at 200 and 400 MeV are reported. Deformation lengths ( δ H = βR ) extracted from angular distributions for the 3 − (2.614), 5 − 1 (3.198 MeV), 5 − 2 (3.709 MeV), 2 + (4.086 MeV) and 4 + (4.324 MeV) states are in good accord with values extracted at other incident proton energies. The fact that the deformation lengths for these levels are independent of incident proton energy within experimental uncertainty provides further support of the validity of the collective DWBA for medium energy proton scattering to strongly excited states. Advantage is taken of this to extract more precise values for the ratio of neutron to proton multipole matrix elements for both the low-lying states and the giant quadrupole resonance at 10.6 MeV.

New Neutron Cross‐Section Measurements at ORELA for Improved Nuclear Data Calculations

The Oak Ridge Electron Linear Accelerator (ORELA) was used to measure neutron total and capture cross sections of aluminum, silicon, chlorine, fluorine, and potassium in the energy range from 100 eV to ~600 keV. These measurements were carried out to support the Nuclear Criticality Safety Program (NCSP). Concerns about the use of existing cross section data in nuclear criticality calculations have been a prime motivator for the new cross section measurements. Our results are substantially different from the evaluated nuclear data files of ENDF/B-VI and JENDL-3.2.

High-Resolution Transmission Measurements of 233U Using a Cooled Sample at the Temperature T=11 K

Abstract For the first time, high-resolution transmission data of 233U have been obtained using a cooled sample. The samples were cooled to T = 11 K using a cryogenic device, which reduced the Doppler broadening of resonances by 50% compared to room-temperature measurements. The measurements were carried out at the Oak Ridge Electron Linear Accelerator over the energy range from 0.6 eV to 300 keV at the 80-m flight path station. Corrections were made for experimental effects, and the average total cross section in this energy range was determined. Results are compared to previous measurements.

High-spin states and band structure inBr76

High-spin states of /sup 76/Br have been investigated through observations of ..gamma.. rays produced in the /sup 66/Zn(/sup 12/C,pn) reaction by bombarding an enriched /sup 66/Zn target with 38.0-MeV /sup 12/C ions. Measurements were made of ..gamma..-ray singles and ..gamma..-..gamma.. coincidence spectra, ..gamma..-ray angular distributions, and ..gamma..-ray linear polarizations. Level energies, decay modes, spins and parities, ..gamma..-ray branching ratios, and ..gamma..-ray radiative admixtures were deduced. There is evidence for a strongly excited ..delta..J = 1 quasirotational band.

Neutron Cross Sections Measurements for Light Elements at ORELA and their Application in Nuclear Criticality

The Oak Ridge Electron Linear Accelerator (ORELA) was used to measure neutron total and capture cross sections of aluminium, natural chlorine and silicon in the energy range from 100 eV to ~600 keV. ORELA is the only high power white neutron source with excellent time resolution and ideally suited for these experiments still operating in the USA. These measurements were carried out to support the Nuclear Criticality Predictability Program. Concerns about the use of existing cross section data in the nuclear criticality calculations using Monte Carlo codes and benchmarks have been a prime motivator for the new cross section measurements. More accurate nuclear data are not only needed for these calculations but also serve as input parameters for s-process stellar models.

High-spin states in Ca 42

Levels in /sup 42/Ca excited by the /sup 28/Si(/sup 16/O, 2p) reaction have been investigated with E16O = 36--42 MeV. ..gamma..-ray angular distributions and ..gamma gamma.. angular correlations relative to the beam direction have been determined. Level energies, decay modes, spins, parities, and ..gamma..-ray radiative admixtures were extracted. Level energies in keV and preferred J/sup pi/s are: 4099.9 (5/sup -/), 5491.4 (5/sup +/), 5744.1 (5/sup -/), 6144.5 (6/sup +/), 6408.8 (7/sup +/), 6553.9 (7/sup -/), 7368.7 (6/sup -/ or 8/sup -/), and 8297.9 (J/sub 7369/ +- 1). These spin-parity assignments differ from those reported recently by Warburton, Kolata, and Olness. (AIP)

High-spin states in /sup 42/Ca. [J,. pi. ]

Levels in /sup 42/Ca excited by the /sup 28/Si(/sup 16/O, 2p) reaction have been investigated with E16O = 36--42 MeV. ..gamma..-ray angular distributions and ..gamma gamma.. angular correlations relative to the beam direction have been determined. Level energies, decay modes, spins, parities, and ..gamma..-ray radiative admixtures were extracted. Level energies in keV and preferred J/sup pi/s are: 4099.9 (5/sup -/), 5491.4 (5/sup +/), 5744.1 (5/sup -/), 6144.5 (6/sup +/), 6408.8 (7/sup +/), 6553.9 (7/sup -/), 7368.7 (6/sup -/ or 8/sup -/), and 8297.9 (J/sub 7369/ +- 1). These spin-parity assignments differ from those reported recently by Warburton, Kolata, and Olness. (AIP)

RIP - General Purpose Interactive Display at HHIRF

RIP is a general purpose interactive code for display and analysis of data acquired with the Holifield Heavy Ion Research Facility (HHIRF) accelerators at Oak Ridge National Laboratory. The HHIRF data acquisition system includes a version of RIP for on-line display of one-and two-dimensional histograms on color graphic terminals and hard copy on color printer/plotters. General features of the program and interactive techniques will be described.

Recent Cross‐Section Evaluations in the Resonance Region at the Oak Ridge National Laboratory

The intent of this work is to present the results and to describe the procedures utilized to evaluate 233U and 19F for criticality safety applications. The evaluation was done in the resolved resonance region using the reduced Reich‐Moore R‐matrix formalism. The resonance analysis was performed with the multilevel R‐matrix code SAMMY, which utilizes the generalized least‐squares technique based on Bayes theory.

R-Matrix Evaluation of 16O Neutron Cross Sections up to 6.3 MeV

We have evaluated 16O neutron cross sections in the resolved resonance region with the multilevel Reich-Moore code SAMMY. Resonance parameters were determined by a consistent analysis, including both Doppler and resolution broadening effects. To properly treat the α particle exit channel, an algorithm to calculate charged particle penetrabilities and shifts was incorporated into SAMMY.