First neutron spectrometry measurement at the HL-2A Tokamak

A compact neutron spectrometer based on the liquid scintillator is presented for neutron energy spectrum measurements at the HL-2A Tokamak. The spectrometer was well characterized and a fast digital pulse shape discrimination software was developed using the charge comparison method. A digitizer data acquisition system with a maximum frequency of 1 MHz can work under an environment with a high count rate at HL-2A Tokamak. Specific radiation and magnetic shielding for the spectrometer were designed for the neutron spectrum measurement at the HL-2A Tokamak. For pulse height spectrum analysis, dedicated numerical simulation utilizing NUBEAM combined with GENESIS was performed to obtain the neutron energy spectrum. Subsequently, the transportation process from the plasma to the detector was evaluated with Monte Carlo calculations. The distorted neutron energy spectrum was folded with the response matrix of the liquid scintillation spectrometer, and good consistency was found between the simulated and measured pulse height spectra. This neutron spectrometer based on a digital acquisition system could be well adopted for the investigation of the auxiliary heating behavior and the fast-ion related phenomenon on different tokamak devices.     

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HL-2A和HL-1M装置采用了激光吹气注入高Z杂质来缓减大破裂中的等离子体电流衰竭,并给出了初步实验结果。在HL-2A装置上建立了利用MHD扰动的参量预报放电破裂先兆的报警系统,研制了MHD实时检测与处理系统,实现了放电破裂先兆的预报、快速触发激光吹气、形成阻性高辐射等离子体、消耗热能和磁能,缓减大破裂。实验证明,这是一种使得大型聚变实验装置在放电破裂之前显著减少等离子体中热能和磁能,而且能安全终止放电的简单、快速和有效的途径。