初始裂变产物鉴别技术研究

In low-energy fission of actinides ,the nuclear split two fragments,at the same time emission prompt-neutron and gamma-ray. The fragements mass energy and charge distributions are important features for fission process research.It was associated with the structure of fissile nuclear ,fission mechanism and systemic rule of charge distribution.With the development of nuclear engergy exploitation,next generation reactors and accelerator drive energy system need more information about fission fragement on device designing ,especially for independed fission yield and delayed neutron data.Therefore,developing a new approach to measure mass energy and charge distributions of fission fragments with high resolution prior to after prompt-neutron emission is indispensable!In this work,we plan to establish one system with two arms for heavy ion species determination in fission fragments.we hope the mass resolution A/ΔA better than 100,and charge resolution Z/ΔZ better than 40 for fission fragments.Hence,this system could be used to fission fragments species direct indentification.It's a new approach for fission fragments measurement,by this technique could research fission process deeply and precise fission-fragment decay studies,also achieve independed fission yields measure future nuclear energy exploitation. This project planning Dual-speed and Dual -kinetic energy associated measurement techniques to realize the fission products particle identification.Micro-channel plate as the time detector for flight time determine, Bragg gas ionization chamber as fragment kinetic energy and ionization ratio determine. Associated the particle flight time and kinetic energy information could confirm fission fragment mass number A ,Bragg detector energy peak value could confirm charge number Z.

初始裂变产物核的质量、动能、电荷分配情况是裂变反应的重要特征，可反映裂变发生初始时刻丰中子核的质量分布、能量分布及瞬发中子多重性等重要裂变信息。实现初始裂变产物核直接鉴别有助于深入了解裂变过程，核裂变电荷分布及产额能量关系系统学规律等。随着核能开发技术的进步，新一代反应堆和加速器驱动核能装置在设计时非常需要裂变核初始裂变产物产额数据。本研究工作拟建立一套双臂重离子鉴别测试系统，对于裂变产物核质量分辨A/ΔA大于100，电荷分辨Z/ΔZ大于40，使其能够运用于初始裂变产物离子直接鉴别，为裂变物理基础研究、核能开发建立新的测试方法。技术方案是采用微通道板探测器精确测定初始裂变产物粒子飞行时间，布拉格气体探测器测定产物粒子动能和比电离峰值，通过粒子飞行时间和布喇格探测器沉积的动能确定产物核的质量数A，布喇格峰值信息测定产物核的电荷数Z，实现初始裂变产物直接鉴别。

裂变产物粒子鉴别技术研究是裂变物理实验方面国际前沿的研究课题。本研究工作采用速度—动能关联技术，建立了重离子质量鉴别新方法，并建成一套裂变产物粒子质量分布测量实验系统。.本课题按照研究计划顺利完成了Cf-252自发裂变源制备，微通道板飞行时间信号拾取探测器研制，真空裂变靶室及飞行管路的设计加工，多参数在线实验数据获取系统建立，飞行时间测量系统时间分辨测量及能量探测器能量分辨测量等研究工作，技术指标达基本达计划书要求，并在此基础上开展了Cf-252自发裂变质量分布测量及初始裂变产物电荷鉴别方法探索。实验结果显示在裂变产额高的峰位位置能够看到明显指征结构，可以区别两个相邻的质量位置，系统质量分辨A/A>100。.本研究工作对速度—动能粒子鉴别技术进行了改进，运用微通道板探测器作为时间信号拾取探测器极大程度地提高了飞行时间测量系统时间分辨，技术水平达到国际先进。Cf-252自发裂变质量分布测量实验结果远优于国外相关实验，整体研究水平达到国际先进。此实验方法的建立为后续开展裂变产物离子电荷鉴别及独立产额数据测量奠定了基础。