Neutron measurement apparatus and neutron measurement method

A neutron measurement apparatus comprising:

• a preamplifier configured to amplify detector output signals from a neutron detector ;
• an AC amplifier configured to amplify alternating current components of the signals output from the preamplifier;
• an analogue filter device configured to remove high frequency components from the signals output from the AC amplifier;
• an AD converter configured to AD-convert the output signals from the analogue filter device at a constant sampling period into digital signals;
• a recorder configured to record the digital signals converted on the AD converter;
• a window function multiplier configured to read out a certain number of the digital signals from the recorder, and to multiply the digital signals by window function coefficients;
• an FFT device configured to apply fast Fourier transform processing to the output signals from the window function multiplier;
• a signal selecting device configured to select and extract only signals having required frequency components based on a calculation result of the FFT device;
• a power spectral density calculator configured to calculate power spectral densities of the signals selected and extracted on the signal selecting device;
• and
• a neutron signal converter configured to convert the output signals from the power spectral density calculator into a neutron measurement value.

A neutron measurement method comprising:

• amplifying alternating current components of detector output signals output from a neutron detector, and applying filtering to the output signals to remove high frequency components from the output signals on an analogue signal processing system;
• digitizing the processed detector output signals at a constant sampling period in a time series on a digitizing processing system;
• applying fast Fourier transform (FFT) processing to the digitized signals in a time domain to convert the signals into signals in a frequency domain on an FFT calculation processing system, and applying filtering to the FFT-processed signals in the frequency domain;
• and
• selecting and extracting signals having required frequency components from the FFT-processed signals in the frequency domain, so as to calculate power spectral densities of the extracted signals, and obtain a neutron measurement value based on the power spectral densities of the extracted signals.