  A Discrete Fourier Transform Method (DFTM) for discrimination between the
signal of neutrons and gamma rays in organic scintillation detectors is
presented. The method is based on the transformation of signals into the
frequency domain using the sine and cosine Fourier transforms in combination
with the discrete Fourier transform. The method is largely benefited from
considerable differences that usually is available between the zero-frequency
components of sine and cosine and the norm of the amplitude of the DFT for
neutrons and gamma-ray signals. Moreover, working in frequency domain naturally
results in considerable suppression of the unwanted effects of various noise
sources that is expected to be effective in time domain methods. The proposed
method could also be assumed as a generalized nonlinear weighting method that
could result in a new class of pulse shape discrimination methods, beyond
definition of the DFT. A comparison to the traditional Charge Integration
Method (CIM), as well as the Frequency Gradient Analysis Method (FGAM) and the
Wavelet Packet Transform Method (WPTM) has been presented to demonstrate the
applicability and efficiency of the method for real-world applications. The
method, in general, shows better discrimination Figure of Merits (FoMs) at both
the low-light outputs and in average over the studied energy domain. A noise
analysis has been performed for all of the abovementioned methods. It reveals
that the frequency domain methods (FGAM and DFTM) are less sensitive to the
noise effects.
