R. R. Doering

An energy-dependent Lane-model nucleon-nucleus optical potential☆

An energy-dependent Lane-model nucleon-nucleus optical potential is presented. The isovector strength parameters of the potential have been determined by fitting (p, n) IAS angular-distribution data between 25 and 45 MeV for targets from 48Ca to 208Pb. The isoscalar strength parameters have been obtained by requiring that the Lane-model potential reproduce the Becchetti-Greenlees Coulomb-corrected proton potential. The energy associated with the proton in all energy-dependent parts of the potential is reduced by the average Coulomb potential inside the nucleus. The main result of the parameter search, other than determining the strength of the isovector energy dependence, is to redistribute the isovector strength found by Becchetti and Greenlees between the real-volume and imaginary-surface terms. The Lane-model optical potential so obtained is reasonably successful in reproducing (p, p), (p, n) IAS, and (n, n) scattering over a wide mass and energy range.

Response functions of organic scintillators to high energy neutrons

Abstract Two cylindrical liquid scintillators of dimensions 5 cm × 5 cm and 12.5 cm × 12.5 cm, filled with NE213, were calibrated with high energy neutrons from E n = 3 MeV to E n = 75 MeV at the time-of-flight facility associated with the Michigan State University Cyclotron. Pulse shape discrimination was used on each detector to separate the protons and alphas produced by neutron interactions from the electrons produced by gamma rays. Response functions for monoenergetic neutrons from about 2 MeV to 75 MeV have been determined. These response functions are very different from the calculated response using the Monte Carlo method. The implications of these calibrations for measurements on high energy neutrons using liquid scintillators are discussed.

Activation and angular distribution measurements of 7Li(p, n)7Be(0.0+0.49 MeV) for Ep=25−45 MeV: A technique for absolute neutron yield determination

Abstract Angular distributions of the combined7Li(p, n)7Be reactions to the ground and first excited state of beryllium have been measured at proton energies of 24.8, 35.0 and 45.0 MeV with a typical accuracy of 5%. The total cross section was also obtained at eleven energies between 24 and 45 MeV by activation techniques. The reaction is a potentially convenient source for neutrons, and absolute neutron fluence can be independent of beam current and target thickness measurement if the amount of 7Be(τ1/2 = 53.4d produced in the reaction is measured. Following the proton irradiation the amount of 7 Be produced is determined by observation of the 0.478 MeV gamma rays from a 10.4% branch of 7Be and this information is combined with the total cross sections and angular distributions to give the neutron fluence at the time of irradiation.

The neutron time-of-flight facility at Michigan State University

Abstract A new neutron time-of-flight facility at the Michigan State University Cyclotron Laboratory incorporates a magnetic beam swinger permitting measurement of angular distributions with a stationary detector. A large volume (2.7 l) liquid scintillation detector with a time resolution of less than 200 ps was developed to exploit the long flight paths (4–32 m) made possible by the swinger. For 33 MeV neutrons an overall time (energy) resolution of 550 ps (≅150 keV) has been achieved.

Production of Neutrons with Protons of 22, 30, and 40 MeV in Stopping Targets of Carbon, Aluminum, Copper, Silver, Tantalum, and Lead

Abstract Stopping targets of C, Al, Cu, Ag, Ta, and Pb were bombarded by protons of 22, 30, and 40 MeV, and the resulting neutron energy spectra were measured down to 0.5 MeV at 30-deg intervals from 0 to 150 deg.

Proton decay of the isobaric analogs of the ground states of207Pb and208Pb

AbstractThe proton decays

Observation of giant Gamow--Teller strength in (p,n) reactions

\tilde p

Comparison of measured neutron spectra with predictions of an intranuclear-cascade model

of isobaric analog states of207, 208Pb in the reactions207, 208Pb(p, n) have been studied using a neutron-proton coincidence technique. The width anomaly observed in (p, n) [4] and (p, n