Double-differential Neutron Emission Cross Sections Research Articles

Measurement of double-differential neutron emission spectra from uranium-238.

We have performed the measurement of neutron emission spectra from 238U using a time-of-flight technique, and deduced the following data; (1) the prompt fission neutron spectra for 2 MeV incident neutrons at two emission angles of 90° and 135°, (2) the double-differential neutron emission cross sections at the incident energies of 1.2, 2.0, 4.2, 6.1 and 14.1 MeV. The emission spectra and the cross sections for scattering process were also deduced by subtracting the fission neutrons from the experimental spectra. The experimental results were compared with other experiments and the evaluations of JENDL-3 and ENDF/B-IV. From the fission spectrum data ranging from 2 to 12 MeV, we have derived the best fit parameters for the Maxwellian and Watt type distribution functions. The experimental spectra are described with the Maxwellian spectrum with temperature of 1.24–1.26 MeV and are softer than both evaluations. The spectra and cross sections for inelastic-scattering showed substantial disagreement with the eva...

Double-Differential Neutron-Emission Cross Sections for7Li and Incident Neutrons between 1.6 and 13.8 MeV

Double-differential neutron-emission cross sections for the /sup 7/Li(n,xn) reaction are presented for average emission angles of 24, 40, 60, 90, 120, and 150 deg. The incident neutron energy covers the range from 1.6 to 13.8 MeV. The cross sections were measured using an electron linear accelerator as a pulsed white neutron source. Elastically scattered neutrons and neutrons scattered via the 0.48-MeV state are treated as one single group. Inelastic scattering cross sections are obtained for the 4.63- and 6.54-MeV states. For this purpose, the underlying neutron continuum coming from competing tritium-producing reactions (three-particle breakup and sequential two-step reaction via the /sup 5/He ground state) is estimated using simple physical model calculations. The data are compared with recent evaluations.

A spectrometer for double-differential neutron-emission cross section measurements in the energy range 1.6 to 16 MeV

A neutron spectrometer for the measurement of double-differential neutron-emission cross sections has been set up. An electron linac (GELINA) is used as a pulsed white neutron source. The energy of the incident neutrons is determined by the time-of-flight method. The secondary neutron spectra are determined by unfolding the pulse-height distributions observed in eight NE213-scintillators surrounding the sample. The measured spectra are normalised to the shape of the incident neutron flux measured with a 235U-fission chamber, and afterwards converted to absolute cross sections using as standard the carbon differential elastic scattering cross section below 2 MeV.

Double-differential neutron-emission cross section for the 7Li (n, Xn) reaction between 1.6–16 MeV

Abstract A neutron spectrometer for the measurement of double-differential neutron-emission cross sections has besn set up. The electron linac GELINA was used as a pulsed white neutron source. The energy of the incident neutrons was determined by the time-of-flight method with a source to sample distance of 60 m. The secondary neutron spectra were determined by unfolding the pulse height distributions as observed in six NE213-scintillators located at 20 cm from the sample. Here we present preliminary results for the 7Li (n,Xn) reaction obtained with a thin sample (0.0325 at/b) for emission angles Θ = 24, 60, 90, 120, 150, 160 degree and for incident neutron energies between 1.6 and 16 MeV. The data have been normalised to the shape of the incident neutron-flux as determined with an 235U fission chamber. The absolute values are based on the differential elastic cross section of 12C below 2 MeV.

Double-Differential Neutron Emission Cross Sections of6Li and7Li at Incident Neutron Energies of 4.2, 5.4, 6.0 and 14.2 MeV

Energy-angle double-differential neutron emission cross sections of lithium isotopes were measured at incident neutron energies of 4.2, 5.4 and 14.2 MeV for 6Li and of 5.4, 6.0 and 14.2 MeV for 7Li using a time-of-flight spectrometer. Care was taken in background subtraction and in data correction for sample-size effects. Detailed comparison of the present results was made with the evaluated data in JENDL-3PR1. A spectrum fitting method was used to extract the 6,7Li(n, n'x)α and (n, 2n) reaction cross sections. Neutrons emitted from the (n, 2n) reactions were well described by the conventional evaporation model. A simple calculation with a final-state Coulomb interaction was effectively applied for the 6,7Li(n, n'x)α reactions. Angle-integrated cross sections of the 7Li(n, n't)α reaction were in good agreement with the JENDL-3PR1 data except the data measured at 6.0MeV. The angular distributions of elastically and inelastically scattered neutrons were successfully analyzed with the coupled-channel method at the incident neutron energy of 14.2 MeV.

Double-differential neutron emission cross sections of 6Li and 7Li at incident neutron energies of 4.2, 5.4, 6.0 and 14.2 MeV.

Energy-angle double-differential neutron emission cross sections of lithium isotopes were measured at incident neutron energies of 4.2, 5.4 and 14.2 MeV for 6Li and of 5.4, 6.0 and 14.2 MeV for 7Li using a time-of-flight spectrometer. Care was taken in background subtraction and in data correction for sample-size effects. Detailed comparison of the present results was made with the evaluated data in JENDL-3PR1. A spectrum fitting method was used to extract the 6,7Li(n, n'x)α and (n, 2n) reaction cross sections. Neutrons emitted from the (n, 2n) reactions were well described by the conventional evaporation model. A simple calculation with a final-state Coulomb interaction was effectively applied for the 6,7Li(n, n'x)α reactions. Angle-integrated cross sections of the 7Li(n, n't)α reaction were in good agreement with the JENDL-3PR1 data except the data measured at 6.0MeV. The angular distributions of elastically and inelastically scattered neutrons were successfully analyzed with the coupled-channel method ...