Production and measurement of a stellar neutron spectrum at 30 keV

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 cross-section 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.