Measurements of Cross-sections of the Neutron Threshold Reactions and Their Usage in High Energy Neutron Measurements at “energy plus Transmutation”

We measured neutron cross-sections of various threshold reactions using different quasimonoenergetic neutron sources. Our motivation for the cross-section measurements comes from the "Energy plus Transmutation" project. In this international project we use neutron activation foils for measurements of high energy neutron field, which is produced during the proton or deuteron irradiation of a thick lead target surrounded by a natural uranium blanket. Au, Al, Bi, In and Ta foils are used as activation detectors, but unfortunately almost no experimental cross-section data for observed threshold (n,xn) reactions are available for higher neutron energies. We prepared a few studies to measure the (n,xn) cross-sections using neutron sources on NPI ASCR cyclotron in Řež and on TSL cyclotron in Uppsala (EFNUDAT program). In these experiments we irradiated above mentioned foils, iodine samples and SSNTD with quasimonoenergetic neutrons from p+Li reaction. First experiments on the Li target were already carried out at NPI with 20 and 25 MeV protons, next irradiations are planned for near future to cover whole available neutron energy region (10-37 MeV) from this source. On June 2008 a measurement at TSL was carried out with energies 25, 50, 100 MeV protons on Li. Activated foils were measured on HPGe detectors and a wide range of spectroscopic corrections was applied. First results of these measurements and their practical importance for the Energy plus Transmutation project will be shown. Finally, complex overview of the results from the last two deuteron experiments on the Energy plus Transmutation setup measured on Nuclotron at JINR by our group from Řež will be provided. Yields of the threshold activation detectors and MCNPX simulations of the setup will be discussed in more detail. I State­of­the­art of the (n,xn) cross­section libraries The present status of knowledge of cross-sections for the (n,xn) reactions is poor. Fig1 and 4 show measured cross-sections for (n,xn) reactions in Bi and Au. In the case of bismuth, reactions from (n,4n) until (n,12n) were measured already (Fig1) [1], but there are values from one experiment only [2]. There are no evaluated data available.