Measurement of differential and angle-integrated cross sections of the 6Li( n,t) 4He reaction in the MeV neutron energy range

Abstract

The cross-section of the 6Li( n,t) 4He reaction has been adopted as a standard neutron cross-section from thermal energy to 100 keV. In the MeV neutron energy region, however, there are large discrepancies among the existing data including experimental and evaluated ones. For example, at 1.0 MeV, the cross section of the 6Li( n,t) 4He reaction in JENDL-3 is 18% larger than that in ENDF/B-VI, and at 1.7 MeV the cross section in CENDL-2 is more than 20% larger than that in ENDF/B-VI. Therefore, new measurements are needed. This paper reports the method and the result of the measurement of the differential and angle-integrated cross-sections of the 6Li( n,t) 4He reaction in the MeV neutron energy range. Differential cross-sections were measured by detecting the forward tritons and forward α particles separately. Cross-sections were derived from differential cross-sections in the center of mass reference system. The detection system was a charged-particle spectrometer based on a gridded ionization chamber (GIC). Experiments were performed at the 4.5 MV van de Graaff accelerator of Peking University, China. Nearly mono-energetic neutrons were produced through the T( p,n) 3He reaction and the D( d,n) 3He reaction. The absolute neutron flux was determined by a 238U foil and a calibrated BF 3 long counter. Our results are compared with other author's data.