Neutron Spectrum Unfolding Using a Modified Truncated Singular Value Decomposition Method

A modified truncated singular value decomposition (MTSVD) is employed to unfold proton recoil pulse-height spectra into neutron energy spectra, using experimentally measured response functions. To illustrate the method, spectra from ²⁵²Cf and ²³⁹PuBe sources are unfolded. The relative error, defined in terms of the 1-norm, using the MTSVD method is found to be approximately half that of the truncated singular value decomposition for the ²⁵²Cf spectra. Relative errors for the ²³⁹PuBe spectra were approximately equal for the two methods. The method is limited by the precision of the measurement of the response functions and the pulse-height spectra. More precise measurements would allow the use of larger truncation parameters and are likely to result in more accurate reconstructed neutron spectra. The MTSVD method is particularly suited to real-time on-line unfolding of spectra.