Measurements of the Neutron-Proton and Neutron-Carbon Total Cross Section from 150 to 800 keV
There have been very few measurements of the total cross section for np scattering below 500 keV. In order to differentiate among NN potential models, improved cross section data between 20 and 600 keV are required. We measured the np and nC total cross sections in this energy region by transmission; a collimated neutron beam was passed through CH2 and C samples and transmitted neutrons were detected by a BC-501A liquid scintillator. Cross sections were obtained with a precision of 1.1-2.0% between 150 and 800 keV using ratios of normalized neutron yields measured with and without the scattering samples in the beam. In energy regions where they overlap, the present results are consistent with existing precision measurements, and fill in a significant gap in the data between En = 150 and 500 keV.
THE N-P SCATTERING CROSS SECTION FROM 90 KEV TO 1.8 MEV
OF DISSERTATION THE N-P SCATTERING CROSS SECTION FROM 90 KEV TO 1.8 MEV There have been very few measurements of the total cross section for n-p scattering below 500 keV. In order to differentiate among NN potential models, improved cross section data between 20 and 600 keV are required. We measured the n-p and n-C total cross sections in this energy region by transmission; a collimated neutron beam was passed through CH2 and C samples and transmitted neutrons were detected by a BC-501A deuterated liquid scintillator. Cross sections were obtained by taking the ratios of normalized neutron yields with the samples in the beam and with no sample in the beam. Both better precision and larger range between 90 keV and 1.8 MeV results are presented. The parameters resulting from fitting effective range theory to the data for n-p scattering are in good agreement with parameters determined from previous fits.
Reactions 7Li + n, 7Li + p and excited states of the A = 8 system
Abstract Integral cross sections of the analogous reactions 7 Li(n, n 1 ) 7 Li, 7 Li(p,p 1 ) 7 Li and 7 Li (p,n 1 ) 7 Be were obtained for neutron energies between 1.0 and 9.0 MeV and for proton energies between 2.0 and 6.0 MeV by observing the γ-radiation emitted from the final states with Ge(Li) detectors. In addition some (n,n 1 ) cross sections on 7 Li were measured for neutron energies around 20 MeV. The (n, n 1 ) excitation function was analyzed in the framework of resonance theory together with existing information on the elastic scattering of neutrons from 7 Li. Two states in 8 Li with the parameters E x ( 8 Li ) = 5.53 MeV , Γ = 0.66 MeV and E x ( 8 Li ) = 6.40 MeV , Γ = 1.14 MeV were clearly observed. The results for 7 Li+p and the question of isospin mixing in 8 Be are discussed in a qualitative manner.