Measurement of neutron total cross sections up to 560 MeV

Abstract

We have completed a new set of total cross section measurements of 31 elements and isotopes spanning the periodic table from Aϭ1 to 238. We employed the same technique as in Finley et al. ͓Phys. Rev. C 47, 237 ͑1993͔͒ with refinements intended to allow measurements on separated isotopes and improved systematic error control. The goal of the new measurement was 1% statistical accuracy in 1% energy bins with systematic errors less than 1%. This was achieved for all but the thinnest samples. Stringent checks of systematic errors in this measurement resulted in a reassignment of systematic uncertainties to the neutron total cross sections reported in Finley et al. Microscopic optical model calculations were carried out to interpret the results of the experiment. Two specific types of optical models were employed. The Jeukenne-Lejeune-Mahaux model was used in the range of 5-160 MeV, and a model based on the empirical effective interaction of Kelly was used from 135 to 650 MeV. These models are shown to be useful for predicting both neutron total cross sections and proton reaction cross sections. They are particularly important for light nuclei, for which standard global phenomenological parametrizations of the optical potential are insufficiently accurate.

Is a global coupled-channel dispersive optical model potential for actinides feasible?

“…Very weak dependence of the geometrical parameters on mass number is observed. Calculations that use the DCCOM potential reproduce the experimental total cross-section difference between 232 Th and 238 U nuclei measured by Abfalterer et al [6] within experimental uncertainty. The isovector terms and the very weak dependence of the geometrical parameters on mass number A give the possibility of extending the derived potential parameters to neighboring actinide nuclei with a great confidence.…”

“…The calculated total neutron cross-section data were used to obtain the ratio R232 Th− 238 U for each of employed potentials. Calculated results were compared with the experimental data of Abfalterer et al [6] in Fig. 1.…”

“…The total cross-section data considered cover all the critical energy points that are necessary for revealing the structure that is due to the Ramsauer effect. Energy-averaged total cross sections σ T for both nuclei obtained from Abfalterer et al [6] from 5 to 200 MeV were used to calculate R232 Th− 238 U and its associated experimental error.…”

“…Recent high-precision measurements of the neutron total cross sections for 232 Th and 238 U nuclei at energies from 5 up to 560 MeV were published by a LivermoreLos Alamos-Ohio University collaboration [6]. The crosssection difference data are presented as the ratio of the measured difference to the average of the individual cross sections: i.e., as R238 U− 232 Th = [σ ( 238 U) − σ ( 232 Th)]/{[σ ( 238 U) + σ ( 232 Th)]/2}.…”

Measurement of Muon Antineutrino Quasielastic Scattering on a Hydrocarbon Target atEν∼3.5 GeV

“…The systematic error on the recoil energy measurement is due to the uncertainty in the MINERvA detector energy scale set by muons and differences between the simulated calorimetric response to single hadrons and the response measured by the test beam program. Additional uncertainties are due to differences between the Geant model of neutron interactions and thin target data on neutron scattering in carbon, iron and copper [39][40][41][42][43][44][45][46]. We evaluate further sources of systematic error by loosening analysis cuts on energy near the vertex and on extra isolated energy depositions, repeating the fit to the background and subsequent analysis, and assigning an uncertainty to cover the difference.…”