Characterization of Deuterated-Xylene Scintillator as a Neutron Spectrometer

We have experimentally characterized the neutron light output response functions of a deuterated-xylene scintillator for neutron energies lower than 10 MeV. We then used the response matrix to unfold the energy distribution of neutrons produced via several reactions, i.e., spontaneous fission, d(d,n) 3 He, 27 Al(d,n) 28 Si, and 9 Be(alpha,n) 12 C. Organic scintillators based on deuterated compounds show a fast response and good gamma-neutron discrimination capability, similar to or better than proton-based scintillators. Deuterated scintillators can also effectively provide neutron energy spectra by unfolding measured data with the detector response matrix, without the need of time-of-flight. Deuteron recoils, produced by elastic collisions between deuterium and impinging neutrons, are preferentially forward-scattered. This non-isotropic reaction results in distinct peaks in the response functions to monoenergetic neutrons. In this work, we evaluated a custom-fabricated 7.62 cm $\times 7.62$ cm deuterated-xylene (EJ301D) liquid scintillator. This liquid has a low volatility and higher flash point, compared to benzene-based deuterated detectors, e.g., EJ315 and NE230. We measured the EJ301D detector neutron response matrix (up to 6 MeV neutron energy) using an intense 252 Cf source and the time-of-flight technique. The number of response functions obtained using our method is only limited by counting statistics and by the experimentally achievable energy resolution. Multi-channel unfolding was then performed successfully for neutron sources with different energy spectra.