A MONOCHROMATIC NEUTRON FACILITY FOR (N,P) REACTIONS

A neutron facility for the study of(n,p) reactions was set up at the I ndiana University Cyclotron Facility. The neutrons were produced by th e reaction Li-7(p,n)Be-7. The energy spread of the neutron beam is dom inated by the thickness of the Li-7 production target. At the (n,p) ta rget the collimated neutron-beam intensity is about 10(5) n/s/cm(2) fo r a 1 mu A proton beam at 120 MeV on a Li-7 target 100 mg/cm(2) thick. The distance between the neutron production target and the (n,p) targ et, 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 degrees, 12.5 degrees, and 17.5 degrees), in three particle telescope s each consisting typically of three hyperpure Ge elements. All three telescopes are mounted in a common cryostat. Spectra are obtained at o ther angles including zero by magnetically deflecting the (n,p) proton s. Spectra recorded at E-n = 118 MeV for (n,p) reactions on several li ght nuclei are presented.