Abstract
The determination of astrophysically relevant neutron-induced cross sections is particularly difficult when the involved isotopes are radioactive or the cross sections are very small. Activation experiments at reactors offer the possibility to overcome these limitations with high neutron fluxes. The flux determination is typically based on the activation of two monitors with known cross sections to separate the different flux components. The usually applied cadmium difference method allows a distinction between the thermal and the epithermal part. By a combination of two linear functions representing both monitors the neutron flux components can be determined. However, if more than two monitors are used, the linear system of equations is overdetermined, which allows the identification of a probability distribution. In this proceeding, the feasibility and relevance of this method is demonstrated.
Highlights
Reactor activations offer the possibility to determine neutron-induced cross sections of astrophysical interest
The neutron flux in a reactor can be divided into a thermal, an epithermal component and a component of fast neutrons
The thermal component can be suppressed with cadmium because cadmium has a high effective cross section for thermal neutrons [1]
Summary
Reactor activations offer the possibility to determine neutron-induced cross sections of astrophysical interest. The difficulties encountered involving small cross sections or radioactive isotopes can be overcome by high neutron fluxes in the reactor. Experiments with epithermal neutrons providing the resonance integral (RI) allow constraints on the effective cross sections in the astrophysically relevant keV range. The (n,γ) effective cross section decreases rapidly with increasing energy, so that the fast neutrons can be neglected. The thermal component can be suppressed with cadmium because cadmium has a high effective cross section for thermal neutrons [1]. Both the thermal and the epithermal part of the neutron flux can be determined by applying the cadmium difference method
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