Neutron scattering differential cross sections for 23Na from 1.5 to 4.5 MeV

Abstract

Measurements of neutron elastic and inelastic scattering cross sections from 23 Na have been performed for sixteen incident neutron energies between 1.5 and 4.5 MeV. These measurements were complemented by γ-ray excitation functions using the (n,n γ) reaction to include excited levels not resolved in the neutron detection measurements. The time-of-flight (TOF) technique was employed for background reduction in both neutron and γ-ray measurements and for energy determination in neutron detection measurements. Previous reaction model evaluations relied primarily on neutron total cross sections and four (n,n 0) and (n,n 1) angular distributions in the 5 to 9 MeV range. The inclusion of more inelastic channels and measurements at lower incident neutron energies provide additional information on direct couplings between elastic and inelastic scattering as a function of angular momentum transfer. Reaction model calculations examining collective direct-coupling and compound absorption components were performed.

Templates of expected measurement uncertainties for (n, xn) cross sections

“…"Monoenergetic" sources produce neutrons using twobody reactions such as 3 H(p, n) 3 He, 2 H(d, n) 3 He, 2 H(t, n) 4 He, 3 H(d, n) 4 He, 7 Li(p, n) 7 Be, 1 H( 7 Li, n) 7 Be, 1 H( 11 B, n) 11 C, 1 H( 15 N, n) 15 O, or 1 H(t, n) 3 He [26,[77][78][79][80][81] typically at university Van de Graaff-type accelerator laboratories (TUNL [30][31][32]43], OU [33,34], UMass Lowell [35], UKY [36][37][38], LBNL [82], the now-defunct Dynamitron at ANL [83], the LICORNE [84,85], the now defunct Ion Source Facility of LANL [86][87][88] and JAERI neutron source [89]). These facilities have moderate precision on both the incident-and outgoing neutron energies.…”

Neutron scattering cross section measurements forFe56

“…It neglects the scattering by air between the sample and detector, which greatly reduces the time required by a true Monte Carlo program. The code has been applied in previous studies mainly on isotopically enriched samples [23][24][25][26][27].…”

“…(2) for the n+ 56 Fe scattering, it was initially applied to n-p scattering from the polyethylene sample to determine the absolute normalization factor, A, using the procedures discussed in Ref. [23].…”

“…The uncertainties in the MUL-CAT calculations for multiple scattering and finite size corrections were estimated to be <5% [23]. This limit was inferred by comparing results between MULCAT and MCNP simulations [28].…”

“…This limit was inferred by comparing results between MULCAT and MCNP simulations [28]. The uncertainty in the detector efficiency was assumed to be 3% [23] . Uncertainties due to counting statistics were typically under 1-2%.…”