Quasi-monoenergetic neutron energy spectra for 246 and 389 MeV (7)Li(p,n) reactions at angles from 0 degrees to 300 degrees

The authors measured the neutron energy spectra of a quasi-monoenergetic (7)Li(p,n) neutron source with 246 and 389 MeV protons set at seven angles (0 degrees, 2.5 degrees, 5 degrees, 10 degrees, 15 degrees, 20 degrees and 30 degrees), 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 2 MeV at 0 degrees and 10 MeV at other angles. The cross-sections of the peak neutron production reaction at 0 degrees were on the 35-40 mb line of other experimental data, and the peak neutron angular distribution agreed well with the Taddeucci formula. Neutron energy spectra below 100 MeV at all angles were comparable, but the shapes of the continuum above 150 MeV 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 degrees, 15 degrees, 20 degrees and 30 degrees) from the 0 degrees data in the continuum part for the 246 and 389 MeV (7)Li(p,n) reactions. It was found that subtracting the dose equivalent at about 20 degrees from the 0 degrees data almost eliminates the continuum component. This method has potential to eliminate problems associated with continuum correction for high-energy neutron monitors. (C) 2010 Elsevier B.V. All rights reserved.