A monochromatic neutron facility for (n,p) reactions

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 10⁵ n/s/cm² for a 1 μA proton beam at 120 MeV on a ⁷Li target 100 mg/cm² 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.