A real-time neutron-gamma discriminator based on the support vector machine method for the time-of-flight neutron spectrometer

A new neutron-gamma discriminator based on the support vector machine(SVM) method is proposed to improve the performance of the time-of-flight neutron spectrometer. The neutron detector is an EJ-299-33 plastic scintillator with pulse-shape discrimination(PSD) property. The SVM algorithm is implemented in field programmable gate array(FPGA) to carry out the real-time sifting of neutrons in neutron-gamma mixed radiation fields. This study compares the ability of the pulse gradient analysis method and the SVM method. The results show that this SVM discriminator can provide a better discrimination accuracy of 99.1%. The accuracy and performance of the SVM discriminator based on FPGA have been evaluated in the experiments. It can get a figure of merit of 1.30.     

Extended Bonner sphere spectrometer for dynamic neutron spectrum on HL-2A

The extended Bonner sphere spectrometer (EBSS) at the HL-2A tokamak for the neutron spectrum is described.This device was developed on the basis of previous Bonner sphere spectrometry (BSS),aiming to obtain a more accurate neutron spectrum in the HL-2A tokamak hall.The previous BSS contained eight Bonner spheres (BS).This EBSS contains 13 3He-filled detectors embedded in polyethylene spheres (PS),pre-amplifiers,and a parallel processing data acquisition system (DAQ).A response matrix is simulated in Geant4 taking the effect of the environment into account.     

Research on the phase adjustment method for dispersion interferometer on HL-2A tokamak

A synchronous demodulation system is proposed and deployed for CO_2 dispersion interferometer on HL-2 A,which aims at high plasma density measurements and real-time feedback control.In order to make sure that the demodulator and the interferometer signal are synchronous in phase,a phase adjustment(PA) method has been developed for the demodulation system.The method takes advantages of the field programmable gate array parallel and pipeline process capabilities to carry out high performance and low latency PA.Some experimental results presented show that the PA method is crucial to the synchronous demodulation system and reliable to follow the fast change of the electron density.The system can measure the lineintegrated density with a high precision of 2.0?×?10~(18)m~(-2).     

基于SVM和DWT的辐射图像局部特征识别方法

针对辐射图像的特点,设计并开发了一种支持向量机（SVM）和基于离散小波变换（DWT）的局部特征识别方法。使用支持向量机解决了辐射图像局部特征提取的困难和分类器对样本数目的要求。而小波的应用使得该算法能够支持多分辨率的特征提取,并提高了总体识别效率。还对比了两种常见的核函数,实验结果表明高斯径向基函数能够取得比较好的分类效果。     

一种针对多机组事故的操作干预水平应急决策辅助系统

操作干预水平(OIL)是指对应于某一特定公众防护行动通用干预水平的易于测量的辐射量,用于在核事故期间直接与监测结果比较给出应急防护行动建议。福岛核事故后,我国核应急准备和响应向着多机组方向发展,本研究提出了一种针对多机组事故优化的OIL应急决策辅助系统,将每个机组发生的事故后果进行单独计算和评价,最后将它们对环境辐射后果的贡献进行迭加并代入原先计算公式中,即得到多机组事故下的OIL值。在优化方法的基础上,系统实现了单机组和多机组事故情景下的OIL查询、计算、修正以及后续的应急辅助决策功能。目前,该系统已应用于秦山、田湾、宁德、阳江等核电基地,其模式和功能在实际应用中得到了不断验证和完善,为核事故应急提供了重要的辅助决策手段和工具。     

Research on the method of dual-frequency microwave diagnosis of plasma for solving phase integer ambiguity

In this work,microwaves and terahertz waves have performed a dual-frequency combineddiagnosis in high-temperature,large-scale plasma.According to the attenuation and phase shift of electromagnetic waves in the plasma,the electron density and collision frequency of theplasma can be inversely calculated.However,when the plasma size is large and the electron density is high,the phase shift of the electromagnetic wave is large (multiple times 2π period).Due to the limitations of the test equipment,the true phase shift is difficult to test accurately or to recover reality.That is,there is a problem of phase integer ambiguity.In order to obtain a phase shift of less than 180°,a higher electromagnetic wave frequency (terahertz wave with 890 GHz)is used for diagnosis.However,the attenuation of the terahertz wave diagnosis is too small (less than 0.1 d B),only the electron density can be obtained,and the collision frequency cannot be accurately obtained.Therefore,a combined diagnosis was carried out by combining twofrequencies (microwave with 36 GHz,terahertz wave with 890 GHz) to obtain electron density and collision frequency.The diagnosis result shows that the electron density is in the range of(0.65–1.5)×10~(19)m~(-3),the collision frequency is in the range of 0.65–2 GHz,and the diagnostic accuracy is about 60%.     

基于概率因果模型与遗传算法的船舶核动力装置故障诊断的新方法

介绍一种将概率因果模型和遗传算法相结合的核动力装置二回路凝给水系统的故障诊断方法,它将概率因果模型的似然函数作为遗传算法的适应函数,从而将复杂系统的故障诊断转化为最优问题。仿真结果表明,该方法能够适应诊断过程中出现的不确定性,并实现多故障诊断,具有较高的诊断可靠性和实用性。