Quasi-monoenergetic neutron energy spectra for 246 and 389MeV 7Li(p,n) reactions at angles from 0° to 30°

The authors measured the neutron energy spectra of a quasi-monoenergetic 7Li(p,n) neutron source with 246 and 389MeV protons set at seven angles (0°, 2.5°, 5°, 10°, 15°, 20° and 30°), using a time-of-flight (TOF) method employing organic scintillators NE213 at the Research Center for Nuclear Physics (RCNP) of Osaka University. The energy spectra of the source neutrons were precisely deduced down to 2MeV at 0° and 10MeV at other angles. The cross-sections of the peak neutron production reaction at 0° were on the 35–40mb line of other experimental data, and the peak neutron angular distribution agreed well with the Taddeucci formula. Neutron energy spectra below 100MeV at all angles were comparable, but the shapes of the continuum above 150MeV changed considerably with the angle. In order to consider the correction required to derive the response in the peak region from the measured total response for high-energy neutron monitors such as DARWIN and Wendi-2, the authors showed the subtractions of H⁎(10) obtained at larger angles (10°, 15°, 20° and 30°) from the 0° data in the continuum part for the 246 and 389MeV 7Li(p,n) reactions. It was found that subtracting the dose equivalent at about 20° from the 0° data almost eliminates the continuum component. This method has potential to eliminate problems associated with continuum correction for high-energy neutron monitors.