Development of fast measurement system of neutron emission profile using a digital signal processing technique in JT-60U

Ishikawa, Masao; Itoga, Toshio*; Okuji, Toshio*; Nakohostin, M.*; Shinohara, Koji; Baba, Mamoru*; Nishitani, Takeo

A line-integrated neutron emission profile is routinely measured using Stilbene neutron detector in JT-60U tokamak. Although the SND has many advantages as a neutron detector, the maximum count rate is limited up to 10 cps due to the analog pulse shape discrimination (PSD) circuit. To overcome this issue, a digital signal processing (DSP) system using a flash ADC has been developed In this system anode signals from photomultiplier of the SND are directory stored and digitized. Then, the PSD between neutrons and rays is performed using software. The DSP system has been installed in the vertical neutron collimator system inJT-60U and applied to deuterium experiments. It is confirmed that the PSD is sufficiently performed and collimated neutron flux is successfully measured with count rate up to 10 cps without the effect of pileup of detected pulses.