Study On The Design Technology Of Double - Flash Spectrometer For The Diagnosis Of Fusion Neutron Spectroscopy

Magnetic confinement fusion (MCF) is one of the most hopeful solutions to the global energy crisis.2.45 MeV and 14 MeV neutrons, generated by fusion reactions of D(d,n)3He and T(d,n)4He, are the only products possible to be measured directly. Neutron diagnostics are useful and reliable for plasma physics research, tokamak operation, blanket design, tritium breeding and radiation protection. The neutron flux monitor and neutron energy spectrometry (NES) diagnosis are two alternatives. In particular, numerous key plasma parameters can be deduced from the neutron energy spectrum, such as the ion temperature, fuel ion isotope ratio, fraction of fast ion, toroidal rotation, and impurity level.High energy resolution and detection efficiency are necessary in NES diagnosis. In this paper, the principle of neutron time-of-flight (TOF) spectrometer is analyzed by simulation and experiment. Finally we have designed and developed a TOF spectrometer. According to the numbers of DD neutrons produced by Experimental Advanced Superconducting Tokamak (EAST), the energy resolution is considered prior, give attention to both detection efficiency.The main work of the paper is as follows.1. The design principles of TOF spectrometer are analyzed. TOF spectrometer uses plastic scintillator detectors, with the first placed in a collimated beam of neutrons, a fraction of which is detected through the proton recoils produced in the scattering process. The second detector is placed a known distance away form the first detector and records a fraction of the scattered neutrons, again through proton recoils. The TOF spectrometer is designed based on a geometry where the first scintillator and the second scintilltor are placed on the constant TOF sphere, with En=2mr2/t2TOF-2. A Monte Carlo (MC) routine is developed for optimizing the dimensions of the scintillators. AMC routine is developed based on A General Monte Carlo N-Particle Transport Code, Version 5 (MCNP5) codes. The cross section data of nuclear reactions are taken form the ENDF/B-VI library. The routine firstly scans the effect of the spectrometer’s dimensions on the time resolution and detection efficiency, including θ、d1、d2、s1、s2、φ、ratio(b/a) and D. Incident neutron energy is set at 2.45 MeV.3. The electronics setup of the designed TOF spectrometer is set up and debugged. The 9214KB PMT is debugged for gain and time resolution. The current corresponding 137Cs incident gamma is measured to determine the thresholds of the first detector and the second detector. The time resolution of TOF spectrometer is measured using the cosmic ray. The result show the time resolution of TOF spectrometer is 500ps.4. A Monte Carlo (MC) routine is developed to improve the SNR based on MCNP5 codes. The SNR in the accelerator room is 4.17:1.5. The energy resolution for DD neutron is 4%, and area detector efficiency for DD neutron is 2.64×10-3cm2.