A monochromatic neutron facility for (n,p) reactions

Abstract

A neutron facility for the study of (n,p) reactions was set up at the Indiana University Cyclotron Facility. The neutrons were produced by the reaction 7Li(p,n) 7Be. The energy spread of the neutron beam is dominated by the thickness of the 7Li production target. At the (n,p) target the collimated neutron-beam intensity is about 10 5 n/s/cm 2 for a 1 μA proton beam at 120 MeV on a 7Li target 100 mg/cm 2 thick. The distance between the neutron production target and the (n,p) target, 3.14 m, makes it possible by time-of-flight to eliminate neutrons degraded below the maximum energy by scattering. Protons from the (n,p) reaction are detected simultaneously at three laboratory angles (7.5°, 12.5°, and 17.5°), in three particle telescopes each consisting typically of three hyperpure Ge elements. All three telescopes are mounted in a common cryostat. Spectra are obtained at other angles including zero by magnetically deflecting the (n,p) protons. Spectra recorded at E n = 118 MeV for (n,p) reactions on several light nuclei are presented.