Measurement of the angle-correlated neutron spectrum for the 9Be(n,2n) reaction with a pencil-beam DT neutron source

The angle-correlated energy differential cross-section for 9Be(n,2n) reaction has been measured with the coincidence detection technique and a pencil-beam DT neutron source of FNS (Japan Atomic Energy Agency). Neutron energy spectra of two emitted neutrons were separately obtained as azimuthal- and axial-angle differential value, which is called TDX. From the measured TDX, double-angle differential cross sections, ADDX, angular differential cross section, ADX, and total cross section, TOX, were deduced. In the TDX, a characteristic energy spectrum for beryllium was seen. The azimuthal ADDX unexpectedly showed a 180 degree symmetrical spectrum, not a flat one. From the result of TOX, JENDL-3.3 and Endf/B-6 showed a little underestimation by around 10%. (authors)