The real-time digital n-γ pulse shape discriminator for the neutron flux monitor on ITER

The Neutron Pulse Shape Discriminator (PSD) is the key part of the Neutron Flux Monitor (NFM) of the International Thermonuclear Experimental Reactor (ITER). The γ signal accompanying the neutron signal should be eliminated in order to get the real neutron flux. A real-time digital PSD (DPSD) method is introduced in this paper. The DPSD is based on the digital technology of the high speed analog to digital converter (ADC) and the Field Programmable Gate Array (FPGA). The discriminator takes the advantage of its parallel and pipeline process capabilities to carry out the real-time sifting of neutrons in fields where both neutron and γ radiations exist. It uses the charge and the slew rate inspection techniques as the discrimination algorithm to obtain good separation of neutron from γ. The experimental results show that the discriminator has excellent discrimination ability and realizes a dead time of zero.