Production and measurement of a stellar neutron spectrum at 30 keV

Abstract

A few years ago, we theoretically studied the production of a stellar neutron spectrum at kT 30 keV using a shaped proton beam impinging on a thick lithium target. Here, we first measure the proton distribution to better control the produced neutron spectrum. Then, we measure the forward-emitted angle-integrated neutron spectrum of the 7Li(p,n)7Be reaction via time-of-flight neutron spectrometry with such proton distribution. The result resembles a stellar neutron spectrum at kT 30 keV. This method avoids in activation experiments the need for spectrum correction. In the case of spherical samples, no knowledge of the crosssection of the isotope being measured by activation would be necessary. Therefore, the present method is of interest for isotopes with unknown or poorly known cross-sections, such as branching points in astrophysics. The key point of our method is the experimental control of the proton distribution that impinges on the lithium target.