  A proton recoil method for measuring D-T neutron energy spectra using
polyethylene film and Si (Au) surface barrier detector was presented. An
iteration algorithm for unfolding the recoil proton energy spectrum to the
neutron energy spectrum was investigated. The response matrixes R of
polyethylene film at 0 degree and 45 degree were obtained by simulating the
recoil proton energy spectra from the mono-energetic neutron using MCNP code.
Under an assumed D-T neutron spectrum, the recoil proton spectra from
polyethylene film at 0 degree and 45 degree were also simulated using MCNP
code. Based on the response matrixes R and the simulated recoil proton spectra
at 0 degree and 45 degree, the unfolded neutron spectra were respectively
obtained using the iteration algorithm, and compared with the assumed neutron
spectrum. The results show that the iteration algorithm method can be applied
to unfold the recoil proton energy spectrum to the neutron energy spectrum for
D-T neutron energy spectra measurement using recoil proton method.
