NEUTRON TIME OF FLIGHT ENERGY SPECTROMETER FOR ICF ION TEMPERATURE DIAGNOSTIC

A current-mode neutron time-of-flight(nTOF) energy spectrometer for inertial confinement fusion(ICF) ion temperature measurements has been designed which will reduce measuring error of fusion neutron energy spectra when the neutron yield is low. The spectrometer consists of a shallow cup-shaped ST1422 fast plastic scintillator with a thicknees of 3mm and full effective volume of 104cm³, a microchannel plate photomultiplier tube(MCP-PMT), a piece of coaxial cable(SUJ-50-7) with a length of 20m, and a transient oscilloscope with a bandwidth of 7GHz. The main performances of the spectrometer and its components have been calibrated. The rise-time and FWHM of the temporal response function are 260ps and 850 ps, respectively. This spectrometer will be used to measure ion temperature in the direct-driven implosion experiments on Sheng-Guang 2 laser facility at Shanghai Institute of Optics and Fine Mechanica(SIOFM) next year.     

CeF3闪烁探测器对五种能量中子的甄别能力研究

用CeF3闪烁体和常用闪烁体ST401分别配特性相同的光电倍增管构成两种闪烁探测器,在1.2MeV、2.5MeV、3.5MeV、5.0MeV和14MeV等能量的稳态中子源场中,测量了这两种闪烁体探测器的电流输出,得到结果表明:上述能量的中子与CeF3闪烁探测器作用形成的电流比同尺寸ST401闪烁体构成探测器的输出电流均低一个量级以上,这些结果与这两种探测器在钴、铯γ源中测量结果比较,可以得出在n、γ混合辐射场中测量γ辐射时,CeF3闪烁探测器能够较好地屏蔽这些能量中子的干扰.     

对γ不灵敏的PIN脉冲中子探测器

将PIN半导体制作成特殊组合结构的PIN脉冲中子探测器,利用三通道装置产生的γ脉冲和中子发生器DT反应产生的14MeV中子脉冲对探测器进行了研究.结果表明:PIN脉冲中子探测器对脉冲γ辐射不灵敏,对脉冲中子辐射的灵敏程度依赖于中子辐射转换靶,探测器的信噪比达到30∶1,是一种在中子、γ混合脉冲辐射场中测量脉冲中子的新型探测器     

A method of detecting capture γ-rays in a strong pulsed radiation field

We present a technology for diagnosing the D－T fusion process by detecting capture γ-rays. This technology provides an alternative route to diagnosing the D－T reaction process when a great deal of heavy Z materials surrounds the D－T region. A very important aspect of this paper is to focus on the methods of shielding low-energy γ-rays whose radiation intensity is 10⁶ times higher than that of the capture γ-rays. Another aspect is about how to distinguish signal from noise. The result of a 50/1 signal-to-noise ratio indicates that the designed double-magnetic spectrograph is very successful for diagnosing the D－T fusion reaction process.     

组合闪烁探测系统的中子能量响应研究

组合闪烁探测系统由"Pb过滤片加塑料闪烁探测器"组成. 采用直流标定方法,实验研究了ST401、ST1422、ST1423组合探测系统对0.565MeV-14.16MeV能量范围的6个能点的中子灵敏度,得到了探测系统的中子灵敏度随Pb过滤片厚度的变化、随闪烁体厚度的变化和随中子能量的变化关系. 利用理论计算和实验测量结果相结合,获得了3种组合闪烁探测系统的中子灵敏度能量响应曲线.     

NEUTRON DETECTOR FOR FUSION BURN HISTORY MEASUREMENTS

We have designed a fast, sensitive neutron detector for recording the fusion history of inertial confinement fusion experiments. With a response time of <40 ps, it was for burn history measurements for deuterium/tritium-filled targets producing as few as ～10⁸ neutrons/shot. The detector is based on the fast rise-time (<20 ps) of BC422 plastic scintillator which, shaped in thin cylinder sheet or curved (in a geometry compensating way) plate, acts as a neutron-to-light converter in a Pb shielding. The Pb shielding shields the scintillator from target X-ray, scattered light and target debris and allows the scintillator to be positioned within 3 cm from the target. The scintillator emits light with wavelengths from 350 to 450 nm. A group of achromatic lens relays the scintillator image along a 1 m optical path to the S20 photocathode of a streak camera outside the chamber. Lens coupling was chosen to give acceptable temporal dispersion. In the design phase, a computer code was programmed to calculate and improve the physical parameters of the optical system, such as light collection efficiency, time dispersion, image position, intensity distribution on the image plane, etc. Some of these parameters were finally measured using a deuterium lamp and a piece of BC422 scintillator activated by X-ray or 0.35 μm laser pulse. The measured results agree well with the prediction of the computer code.     

激光直接驱动内爆DT燃料面密度诊断

在神光Ⅱ基频光直接驱动内爆实验中,利用CR39径迹探测器测量了DT靶丸释放出的14MeV中子弹性散射后逃逸出燃料的反冲D核和反冲T核的数量,实现了激光聚变实验中燃料面密度〈ρR〉的诊断.测量结果表明,靶面激光照射均匀度对压缩状态具有一定程度的影响,爆推靶〈ρR〉低于烧蚀靶〈ρR〉一个量级左右,表明烧蚀靶压缩情况比爆推靶好,超热电子预热严重影响压缩 关键词： 惯性约束聚变 等离子体诊断 燃料面密度 CR39     

中子复合靶室系统的研究

根据脉冲裂变中子测量对探测系统中子灵敏度的要求，改变了传统的中子靶室探测系统的设计模式，采取最优设计方案，设计了反冲法和裂变法结合的复合靶室装置，建立了两种测量靶室组合成为靶室主体长度仅为1．1m而且需要静态真空系统的中子复合靶室装置。测量靶室系统由“靶室主体、靶室支管、辐射体和PIN电流型探测器”组成，反冲法使用的辐射体是聚乙烯薄膜(CH2)，裂变法使用的辐射体是^235U辐射体。