吸收法在强激光与固体靶所致脉冲X射线能谱测量中的研究进展北大核心CSCD

脉冲X射线能谱测量,对于强激光装置中的物理诊断以及辐射防护具有重要意义。脉冲X射线具有脉冲时间短、注量大、能谱范围宽等特点,常规脉冲测量技术往往受到探测器死时间、堆积效应的限制而无法适用。目前多个国家都建立了强激光装置的研究平台,并开展X射线能谱测量相关研究。本文首先介绍了基于吸收法原理且适用于中低能脉冲X射线的测量方法:Ross Pair法和衰减法。然后针对这两种方法从5个方面(探测器结构、滤片材料、探测介质选择、散射控制以及解谱方法)综述了脉冲X射线吸收谱仪的研究进展,并分析了各自的适用性。目前激光装置中脉冲X射线能谱的测量还面临着能量分辨率不理想、结果不确定度无法量化和被动式能谱测量操作不便等问题。随着激光装置的不断升级,脉冲X射线注量以及打靶频次将不断增加,对探测器的耐辐照性能以及响应速度提出了更高的要求。     

总能量为40J的“预-主”脉冲激光驱动的波长为32.6nm的类氖―钛离子软X射线激光(英文)

利用脉宽为 650 ps,主脉冲能量仅有 40 J 的驱动激光,演示了类氖―钛离子 J=0→1, 3p→3s 跃迁、波长为 32.6 nm 的软 X 射线激光。所用能量比以前用于低 Z 元素类氖―离子 X 射线激光的驱动能量低约一个量级。为了确定类氖―钛 X 射线激光产生的驱动能阈值,进行了一系列平板钛靶的实验。实验中,靶长采用 1.8 cm,驱动源为“星光”装置输出的波长为 1.05 μm 的激光脉冲,而“预-主”脉冲间隔为 5 ns,当预脉冲能量为主脉冲能量的 1%时,X 射线激光产生的阈值能量为 40 J,当预脉冲能量为主脉冲的 9%时,阈能量则为 110 J。1%和 9%两种预脉冲条件下,波长为 32.6 nm 的类氖―钛 X 射线激光线峰值偏转角均为 5 mrad,而发散角则分别为 4 mrad 和 5 mrad。     

高压X射线衍射的脉冲激光加热方法

相对于传统的连续激光加热方法,脉冲激光加热能够显著缩短加热时间,从而有效阻止金刚石样品腔内各组分的化学反应。基于北京同步辐射装置(Beijing synchrotron radiation facility,BSRF)高压实验站原有的连续激光加热系统,建立了可应用于高压X射线衍射实验的脉冲激光加热方法。该方法利用信号发生器对脉冲激光器、测温电荷耦合器件(Charge Coupled Device,CCD)光谱仪以及X射线探测器进行同步控制,实现了脉冲激光对样品加热,并在加热周期内完成温度谱及高压衍射数据的同步采集。利用高压条件下的Pt样品,对脉冲激光加热过程中样品的温度稳定性、重复性以及温度梯度进行了测试,并完成了原位X射线衍射实验。该脉冲激光加热系统的搭建,为在BSRF高压实验站开展原位脉冲激光加热方法研究提供了条件,也为将来在北京高能同步辐射光源上实施相关方法奠定了基础。     

便携式脉冲X射线成像系统研制

便携式脉冲X射线成像系统主要由脉冲X射线源、数字化记录系统和笔记本电脑组成，介绍了系统的硬件(脉冲源和图像采集控制卡)和应用软件的设计过程。仪器剂量小、质量小、成像质量高，目前已运用到公安系统的安全检查等部门。     

XRF方法在测量纸张厚度中的应用

本文的目的是研究XRF法在纸张厚度测量上的应用.采用X射线荧光吸收法和源初级射线散射法分别对一批纸张样品质量厚度进行测量,并对测量结果进行对比,作出有益的讨论.测量是采用成都微子科技有限公司的IED-2000P型手提式多元素X射线荧光分析仪,探测器选用Si-PIN电致冷半导体探测器,同位素源采用双激发源(238Pu).实验表明:X射线荧光吸收法在纸张厚度测量上的准确度要比源初级射线散射法好,采用源初级射线散射法对于纸张厚度的测量也是可行的.     

准点X光源实验台架的研究进展

<正>为了研究医学系统中脉冲X射线对乳腺癌诊断的关键技术,研制了一台脉冲准点X光源系统,准点X光源实验台架示于图1,其由脉冲源、脉冲X射线管和光学聚焦透镜组成。脉冲源采用紧凑可移动化的设计,其由Marx发生器、火花隙开关、电容分压器及输出段构成。脉冲X射线管的设计     

高功率KrF准分子激光及束靶相互作用研究进展

6束角多路高功率KrF系统经运行考验,对MOPA系统光学元件、激光开关、同步高压脉冲触发系统等影响系统稳定的因素进行了改进。经专家小组检查,实测电子束能量不稳定性小于5％,激光能量稳定性可达到5％～10％（每炮能量重复）。 用此系统的一束激光（30J/23ns）配合上海光机所进行了受激喇曼散射（SRS）实验,脉冲宽度压缩实验效率约为17％,脉宽压缩15倍。此外,在前端进行了受激布里渊散射（SBS）压缩脉宽研究工作。 进行了束靶作用初步实验,包括X射线针孔照像、离子飞行时间测量以及探测器（光电     

单光子入射方法测量超快硬X射线能谱

利用单光子入射方法测量了高强度超短脉冲激光 (1 3 0fs,1 0 16 W cm2 ,744nm)与固体等离子体相互作用产生的超快 (ps)硬X射线 (>3 0keV)能量连续谱。采用铅屏蔽、激光脉冲和线性门同步符合技术将HPGeX射线谱仪的本底计数率降低到 1 0 -4 炮 ,满足了单光子计数时的低本底要求。用该谱仪实际测量了激光等离子体产生的超快硬X射线能谱 ,所得结果与理论预期符合。     

水底沉积物原位X射线荧光测量中水分的影响与校正

论述了水底(海底、湖底或水系)沉积物中含水量的变化对原位X射线荧光测量的影响,以源初级X射线在沉积物上的相干散射线和非相干散射射线强度为内标建立的散射校正方程,可有效地克服沉积物中含水量变化对目标元素特征X射线的干扰。实验结果表明,对铜矿远景区土壤样品,当样品中含水量变化为20％时,目标元素(Fe：10．9％;Cu：300mg／kg;Zn：124mg/kg)特征X射线强度的变化小于5％。     

强激光与固体靶相互作用所致硬X射线剂量和能谱的实验测量

为了研究强激光与固体靶相互作用产生的电离辐射危害,本文在星光Ⅲ300TW强激光装置上开展了一系列激光打靶实验。实验使用的激光功率密度为5×10~(18)~4×10~(19)W/cm~2,激光脉冲能量为60~153J,靶为直径1mm、厚度1mm的Ta圆柱,本文分别对X射线剂量、X射线能谱和超热电子能谱进行了测量。实验结果表明,测量到的单发最大X射线剂量约为16.8mSv,靠近激光传播方向(0°),距靶50cm处;激光0°方向的X射线剂量随激光功率密度的增加而显著增加,激光90°方向的X射线剂量随激光功率密度的变化相对较小;测量到的X射线能谱可大致用含有两个X射线温度的指数分布函数描述,其中0°方向测量到的X射线温度为0.4~1.15 MeV,90°方向测量到的X射线温度为0.25~0.54 MeV;实测超热电子温度与Wilks定标率符合较好。     

SINAP激光同步辐射源实验装置方案研究

本文在考虑相互作用区内电子束和激光束横向发散的前提下,推导了激光同步辐射源X射线通量的计算公式,讨论了激光束和电子束束腰尺寸对X射线通量和谱通量的影响。根据谱通量最大原则选取相互作用区电子束和激光束的横向尺寸,分析了基于中国科学院上海应用物理研究所（SINAP）的皮秒、飞秒电子直线加速器的激光同步辐射实验装置的性能。     

Direct computation of lss parameters for the prediction of fission-fragment ranges and energy-loss in any substance

Analysis of extensive experimental range and energy loss data of ²⁵²Cf fission fragments in gases and solids reveals large discrepancies between the ranges calculated according to LSS theory and the experimental data. The same applies also to experimental energy loss data. A modified LSS expression which is based on these results enables the prediction of range and energy loss data for ²⁵²Cf fragments in any substance. Both the original LSS expressions and the modified expressions used to involve an interpolation procedure and iterative processes.Based on extensive experimental range and energy loss data a direct method for calculating the LSS parameters is introduced, eliminating the need for the interpolation procedure and the iterative process.     

Experimental Study of the X-Ray Radiation Source at Approximately Constant Radiation Temperature

An X-ray radiation source with approximately constant radiation temperature is realized by irradiating golden hohlraum with a shaped laser pulse. A simple theoretical model based on power balance is used to design the shape of the drive laser pulse. Experiments are carried out on the Shenguang III prototype laser facility, and the experimentM results are presented for radiation sources with the flat-top lasting about 2.5 ns at two different peak temperatures of about 150 eV and 170 eV, respectively, including the the drive laser pulses and the time integrated possible improvements are discussed. time histories of the temperatures, the shapes of radiation spectra. The validity of the model and     

The Electron Trajectory in a Relativistic Femtosecond Laser Pulse

In this report, we start from Lagrange equation and analyze theoretically the electron dynamics in electromagnetic field. By solving the relativistic government equations of electron, the trajectories of an electron in plane laser pulse, focused laser pulse have been given for different initial conditions. The electron trajectory is determined by its initial momentum, the amplitude, spot size and polarization of the laser pulse. The optimum initial momentum of the electron for LSS （laser synchrotron source） is obtained. Linear polarized laser is more advantaged than circular polarized laser for generating harmonic radiation.     

A Comprehensive Time-Resolved Study of X-Ray Signals in a 4?kJ Dense Plasma Focus Facility

In the present research, time-resolved of X-ray signals are investigated in a 4?kJ PF device using five filtered PIN-diodes and a Scintillation detector. At applied voltage 12?kV using nitrogen (N₂) gas, the optimum pressures for maximum yield of HXR and SXR emission were 3?torr and 4?torr respectively. At each operating pressure, multiple pulses in SXR signals with respect to amplitude and duration of emission were studied in a time span of 700–800?ns. According to energy response of filters used, the origin of X-ray pulses and also the approximate energy of X-ray photons were analyzed. It was found that at higher pressure 4?torr, the yield of SXR photons in different pulses increases 20–30% in comparison with the results obtained at pressure 3?torr while the yield of HXR decreases. The results confirm that the operating pressure is an effective parameter on the yield of SXR and HXR emitted from this device.     

X-RAY and Gamma Intensity Measurement

A method for developing a graph of radiation intensity vs. time for a pulse of X-ray or gamma radiation is presented. The method has been used for determining radiation intensities from pulses of nanoseconds duration with intensities in the 1010 to 1011 roentgens/sec range. It is applicable to pulses of different durations and intensities.     

利用多毛细管准直器测量X射线光源焦斑尺寸

设计了一种测量X射线光源焦斑尺寸的方法：多毛细管准直器法。整体玻璃毛细管X射线准直器是由数10⁵根内径为几微米的单玻璃毛细管组成的X射线光学器件,X射线光源发出的发散X射线光束被多毛细管准直器约束后变为准平行束。准平行束的截面直径是X射线光源焦斑直径的函数,通过测量准平行束不同位置处的截面直径,利用线性拟合可得到X射线光源的焦斑直径。分别利用多毛细管准直器法和常用的小孔成像法测量了同一微焦斑X射线光源的焦斑直径,测量结果分别为60.8和59.4μm。多毛细管准直器法对焦斑直径在亚微米量级或更小X射线源的焦斑尺寸测量中将显示出更多的优势。     

聚变堆第一壁TiC涂层材料研究

本文介绍了第一壁ＴｉＣ涂层材料的化学气相沉积（ＣＶＤ）工艺；研究了涂层工艺条件对涂层微观结构、沉积速率和基体对涂层生长的影响；给出了涂层厚度与涂层工艺条件之间的经验关系式。讨论了ＴｉＣ／石墨、ＴｉＣ／ＭＯ、ＴｉＣ／３１６ＬＳＳ涂层材料的电子束热冲击损伤机理和热疲劳损伤机理，并对ＴｉＣ／石墨、ＴｉＣ／Ｍｏ、ＴｉＣ／３１６ＬＳＳ用做现行Ｔｏｋａｍａｋ第一壁材料的可行性进行了分析。     

岭澳核电站二期反应堆核测量相关系统设计

分析岭澳核电站二期反应堆核测量各相关系统的主要特点,阐述核仪表系统(RPN)、堆芯中子注量率测量系统(RIC)、冷却剂丧失事故(LOCA)监测系统(LSS)与数字化仪表控制系统(DCS)的功能划分和接口设计方案。岭澳核电站二期设计方案针对RPN、RIC、LSS不同的功能需求和特点,有效地利用数字化仪表控制平台的优势,灵活采用3种与DCS的功能分配和接口划分方案,更好地实现了故障诊断和逻辑功能处理。     

Time-Dependence of Cold Neutron Pulse Emitted from Methane at 20°K

The time-dependent behavior of monochromatic neutrons from a pulsed cold moderator system provides important information for application of the system as a pulsed cold neutron source. The time distribution of neutron pulses from 20°K methane has been studied using time-of-flight and crystal monochromator techniques. The first time-moments of the neutron pulses and the thermalization time constant have been obtained.