  A self-adaptive differential evolution neutron spectrum unfolding algorithm
(SDENUA) was established in this paper to unfold the neutron spectra obtained
from a Water-pumping-injection Multi-layered concentric sphere Neutron
Spectrometer (WMNS). Specifically, the neutron fluence bounds were estimated to
accelerate the algorithm convergence, the minimum error between the optimal
solution and the input neutron counts with relative uncertainties was limited
to 10-6 to avoid useless calculation. Furthermore, the crossover probability
and scaling factor were controlled self-adaptively. FLUKA Monte Carlo was used
to simulate the readings of the WMNS under (1) a spectrum of Cf-252 and (2) its
spectrum after being moderated, (3) a spectrum used for BNCT, and (4) a reactor
spectrum, and the measured neutron counts unfolded by using the SDENUA. The
uncertainties of the measured neutron count and the response matrix are
considered in the SDENUA, which does not require complex parameter tuning and
the priori default spectrum. Results indicate that the solutions of the SDENUA
are more in agreement with the IAEA spectra than that of the MAXED and GRAVEL
in UMG 3.1, and the errors of the final results calculated by SDENUA are under
12%. The established SDENUA has potential applications for unfolding spectra
from the WMNS.
