Experimental study of the149Sm(n, α) reaction with thermal neutrons

The cross section of the¹⁴⁹Sm(n, a) reaction for several alpha transitions has been measured. Using an arrangement where only the target is situated in the beam while the detector is placed in some distance aside, the influence of a high background has been successfully eliminated. A detailed analysis of the background has been performed. The obtained resolution in the alpha particle energy (FWHM=65 keV) makes it possible to distinguish seven transitions for which average cross sections for the thermal neutron spectrum withT= 400 °K have been evaluated.