A new method for generating in a moderator the Maxwellian neutron spectra for stellar temperatures

To verify the modern scenario of nucleosynthesis, one has to know neutron capture cross sections of every heavy- and medium-weight nucleus for the Maxwellian neutron spectra at stellar temperatures, that is in the neutron energy region of about several tens keV. We propose a new method for generating Maxwellian-type neutron spectra in a moderator for different temperatures from 10 to 50 keV. To create the spectrum, we propose to use the reactions 7Li(p,n) or T(p,n) as the neutron source and a special form of the moderator (graphite or lead). The results of optimising the moderator form and its dimensions are discussed in the present report. The new method allows direct measurement of cross sections for Maxwellian neutron spectra and use of the activation method for measurements of the capture cross sections of very small samples or for nuclei with small cross sections. (orig.)