The Design and Optimization of a Neutron Time-of-Flight Spectrometer with Double Scintillators for Neutron Diagnostics on EAST

Abstract

Neutron energy spectrometry diagnosis plays an important role in magnetic confinement fusion. A new neutron time-of-flight (TOF) spectrometer with double scintillators is designed and optimized for the EAST tokamak. A set of optimal parameters is obtained by Monte Carlo simulation, based on the GEANT4 and ROOT codes. The electronic setup of the measurement system is designed. The count rate capability is increased by introducing a flash ADC. The designed spectrometer with high resolution and efficiency is capable of being applied to fusion neutron diagnostics. Applications in mixed-energy and continuous energy neutron fields can also be considered.

High-precision digital time-amplitude analysis system for the neutron Time-Of-Flight spectrometer in HL-2M

“…We installed a cylindrical EJ-299 scintillator crystal with a diameter of 5.2 cm and a thickness of 6 mm into a tapered light guide. The scintillator detector was exposed to a 241 Am- 9 Be neutron source (manufactured in 1978 with a radioactive activity of 2.0 × 10 8 Bq), and the PMT output signal was connected to the S1 plugin and ultimately analyzed by the DTAA system. The threshold was set to 150 keV, and the neutron-gamma discrimination function was enabled.…”

“…The rise time and pulse width of a single neutron pulse are approximately 5 ns and 20 ns, respectively. Meanwhile, using Geant4, we simulated the irradiation of a single layer of EJ-299 scintillator by the 241 Am- 9 Be neutron source, and the resulting pulse height spectra from both the experiment and the simulation were plotted in figure 5.…”

“…As observed in figure 5, the simulated results closely match the experimental results, and most of the pulse amplitudes are low and there are no clear peaks. This is mainly due to the high energy of the 241 Am- 9 Be neutron source and the thinness of the scintillator crystal. Most of the detected neutrons only undergo one collision, and their energy is mostly carried away by scattered neutrons, resulting in the low pulse amplitudes.…”

“…To further improve the energy resolution of the spectrometer, the double-ring neutron TOF spectrometer has been developed by increasing the number of S2 detectors [9,10]. it has a double-ring structure that reduces the length of the S2 detector.…”

“…Figure 5. Amplitude spectrum obtained from the S1 scintillation detector for 241 Am-9 Be neutron source measurement using the DTAA system in laboratory environment.…”