Development of the real-time double-ring fusion neutron time-of-flight spectrometer system at HL-2M

A real-time double-ring neutron time-of-flight (TOFII) spectrometer system has been proposed to achieve plasma diagnosis on HL-2M tokamak with a relatively high count rate and sufficient energy resolution. The TOFII system is in its development stage, and this work describes its characteristics in terms of design principle, system structure, electronic system design, preliminary tests, and neutron transport simulation. The preliminary test results illustrate that the TOFII system can demonstrate the real-time dynamic spectrum every 10 ms. The results also show that based on the support vector machine method, the n–γ discrimination algorithm achieves the discrimination accuracy of 99.1% with a figure of merit of 1.30, and the intrinsic timing resolution of the system is within 0.3%. The simulated flight time spectrums from 1 to 5 MeV are obtained through the Monte Carlo tool Geant4, which also provide the reasonable results. The TOFII system will then be calibrated on mono-energetic neutron sources for further verification.