丝阵Z箍缩1维X射线辐射功率分布的数据处理

在丝阵Z箍缩实验中利用CCD记录X射线辐射功率的1维时空分布图像,对光纤传输效率、图像聚焦、MCP与CCD的耦合效率等因素造成的图像失真进行了处理,利用实验实测的单光纤点扩展图像和光传输效率曲线对辐射功率分布图像进行处理,并修正光纤传输效率以及MCP和CCD间耦合效率不均匀性的影响以还原X射线辐射功率的1维空间分布信息。处理后将图像沿空间积分获得了与X射线功率谱仪相吻合的X射线辐射功率脉冲波形,同时不同发次由两系统得到的X射线波形的前沿之间也表现出了良好的一致性。     

基于光锥耦合的X射线像增强器

利用光锥的无畸变传输特性,将它作为光学中继元件,以光敏胶为耦合介质,把X射线像增强器和电荷耦合器件(CCD)耦合起来,组成X射线成像器件。探讨了光锥与CCD的耦合工艺,给出了耦合过程中的关键技术并通过实验分析了空气和光敏胶作为耦合介质对光锥与CCD耦合效率的影响。实验表明,X射线成像器件的空间分辨率达到3.5 lp/mm,对人体的X射线透视成像效果好,能够满足小幅面的医学成像和无损检测的要求。     

X光高分辨探测用CsI(Tl)晶体的蒙特卡罗模拟研究

提出了一种基于CsI(Tl)闪烁晶体和面阵CCD器件、采用光纤和光纤面板进行光耦合及传输、以扇形束线阵扫描方式实现对X光高分辨探测的方案。CsI(Tl)晶体的尺寸大小将直接影响到晶体的发光效率及X光的高分辨探测,据此开展了蒙特卡罗模拟研究。模拟研究了X射线能量、X射线源到探测晶体的距离(源距)、CsI(Tl)晶体的厚度与X射线能量分布、全能峰效率与CsI(Tl)闪烁晶体转换效率之间的关系。结果表明,当X射线能量为120~450 keV,CsI(Tl)晶体尺寸厚度为0~1.5 cm变化时,全能峰效率的变化范围为31.34~96.74%,CsI(Tl)闪烁晶体的转换效率的变化范围为12.8~97.43%。可见,X射线的能量及CsI(Tl)闪烁晶体尺寸的厚度,是决定X光高分辨探测的重要参量,这对优化X光高分辨探测用CsI(Tl)晶体的尺寸设计具有一定的参考价值。     

长脉冲keV X射线源的辐射特征

 利用神光Ⅱ第九路2 ns长脉冲激光束作用厚钛固体靶,研究了产生的keV X射线源的辐射区域和总辐射功率的时间行为。结果表明：在长脉冲激光作用厚固体靶时,硬X射线线辐射功率的时间行为以及辐射体积的时间行为与激光脉冲波形一致;长脉冲时,等离子体2维膨胀效应非常显著,keV X射线线辐射的径向辐射区域在激光焦斑尺寸附近达到饱和,导致X射线线辐射功率出现饱和,且keV X射线线辐射的辐射体积正比于焦斑尺寸的3次方。从理论和实验角度研究了在同样入射激光能量下,辐射功率随激光焦斑尺寸的变化关系,发现keV X射线线辐射的饱和辐射功率正比于焦斑尺寸的5/3次方,理论结果与实验结果一致。并讨论了相同基频输出激光能量下,keV X射线辐射总功率随激光波长的变化关系,发现即使考虑了倍频效率的影响,短波长激光仍然有利于keV X射线的发射。     

长脉冲keV X射线源的辐射特征

利用神光Ⅱ第九路2 ns长脉冲激光束作用厚钛固体靶,研究了产生的keV X射线源的辐射区域和总辐射功率的时间行为。结果表明：在长脉冲激光作用厚固体靶时,硬X射线线辐射功率的时间行为以及辐射体积的时间行为与激光脉冲波形一致;长脉冲时,等离子体2维膨胀效应非常显著,keV X射线线辐射的径向辐射区域在激光焦斑尺寸附近达到饱和,导致X射线线辐射功率出现饱和,且keV X射线线辐射的辐射体积正比于焦斑尺寸的3次方。从理论和实验角度研究了在同样入射激光能量下,辐射功率随激光焦斑尺寸的变化关系,发现keV X射线线辐射的饱和辐射功率正比于焦斑尺寸的5/3次方,理论结果与实验结果一致。并讨论了相同基频输出激光能量下,keV X射线辐射总功率随激光波长的变化关系,发现即使考虑了倍频效率的影响,短波长激光仍然有利于keV X射线的发射。     

X射线光阴极量子效率的研究

从理论上分析了阴极材料密度分布对CsI/MCP反射式X射线光阴极量子效率的影响，制备了不同密度分布的CsI/MCP反射式X射线光阴极，通过实验测试，优化出了最佳密度分布结构。     

X射线辐射输运分解实验研究

在“星光Ⅱ”激光装置上进行了X射线辐射输运分解实验研究.实验中利用高时空分辨的MCP选通X射线皮秒分幅相机和软X射线条纹相机从缝口观测腔内壁X射线辐射时空分布,得到X射线在腔中的输运速率、X射线持续发射时间和轴向强度衰减量;利用X射线CCD针孔透射光栅谱仪观测到腔内X射线辐射光谱随空间位置的变化,得到X射线在输运过程中被多次吸收和发射后谱的变化特征;用X射线二极管和亚千X射线能谱仪分别得到源和输运末端X射线辐射总量和辐射温度.介绍了实验中采用的诊断技术和实验方法,并给出了获得的典型结果. 关键词：     

光纤耦合GAGG＿Ce型X射线探测器高分辨成像

闪烁屏信号串扰是影响X射线探测器空间分辨率的主要因素,基于点扩散函数理论对光纤耦合GAGG_Ce单晶闪烁屏型CCD/CMOS探测器的空间分辨率进行了研究。利用蒙特卡罗程序EGSnrc和光学仿真软件Zemax分别对GAGG_Ce单晶闪烁屏射线串扰和荧光串扰进行了仿真。仿真结果表明,对于低能X射线辐射成像,荧光串扰是影响探测器空间分辨率的最主要因素。此外,研究了通过降低光纤面板数值孔径以抑制荧光串扰的方法,得到了光纤面板数值孔径与探测器空间分辨率和X射线转换因子间的关系,并通过自制CCD探测器测试验证了仿真结果的正确性。     

脉冲激光在光纤中时间波形传输特性研究

给出了光纤传输激光脉冲波形特性测试的实验光路图,对比测量了经过空气传输和光纤传输两种方式的脉冲波形。实验测试了光束耦合到不同长度的单模和多模光纤与经空气传输后的时间脉冲波形,得到了激光脉冲波形的精细结构。实验结果表明,所选的多模和单模光纤经数百米传输后的脉冲展宽在容许误差范围之内,说明所选用的光纤可以作为纳秒激光时间脉冲波形测试的理想传输介质。     

软X射线能谱定量测量技术研究

采用每毫米1000线的自支撑透射光栅配上背照射软X射线CCD(charge coupled device)组成了透射光栅谱仪,利用北京同步辐射装置(BSRF)3W1B光束线软X射线实验站上X射线源分别对透射光栅的衍射效率和软X射线CCD的响应灵敏度进行了准确的实验标定,获得了150eV到1500eV能区的绝对衍射效率和响应灵敏度的实验结果;同时在国内外研究工作的基础上,发展了自己的透射光栅衍射效率理论计算模型和X射线CCD响应灵敏度计算模型,开展了相应的理论计算和实验标定结果比对工作,理论和实验符合较好,     

Potential of GAGG:Ce scintillation crystals for synchrotron X-Ray micro-imaging

We examined the use of cerium-doped gadolinium aluminum gallium garnet (GAGG:Ce) as a material for scintillation screens in synchrotron X-ray radiography (SXR). Highlighted for gamma-ray detection, GAGG:Ce is also an attractive material for SXR because of its high X-ray stopping power and the high light yield at around 530?nm. A thin and transparent screen prepared from our grown ingot of GAGG:Ce was compared with commonly used scintillators of CdWO₄ and YAG:Ce in terms of image quality under monochromatic X-ray illumination. Micron spatial resolutions were achieved with comparable image quality, suggesting that a single crystal of GAGG:Ce is competent scintillation material for SXR.     

Optimization of neon soft X-rays emission from 200 J fast miniature dense plasma focus device: A potential source for soft X-ray lithography

The neon soft X-ray (SXR) emission characteristics of a Fast Miniature Plasma Focus (FMPF-3) device have been investigated. The FMPF-3 device used for our experiment is of sub-kilojoule energy capacity, which is an order of magnitude lesser than the other well established plasma focus devices. The influence of different geometrical parameters of the anode and the pressure of the filling gas on the SXR emission was investigated to optimize the neon SXR yield and thereby make it a potential source for X-ray lithography. The SXR signal, solely from the desired, characteristic spectral range (900–1600) eV was selectively extracted and acquired using appropriate X-ray absorption filters on diode X-ray spectrometer. It was found that the neon SXR emission from 17 mm long cylindrical anode, which produced best neutron yields, was rather poor, in a very narrow pressure range and that too at low operating pressure. With decrease in the length of cylindrical anode, the optimum operating pressure shifts to higher pressure side, the working pressure range widens and the SXR yield also increases until the anode length is reduced to 12 mm, after which, the SXR yield and working pressure range start to degrade. The highest neon SXR yield of 1.1 J/shot, corresponding to a wall plug efficiency of 0.57%, was obtained for 12 mm long cylindrical anode. The tapered anodes with different length were also designed and tested, but they did not show any significant improvement in neon SXR yield.     

纤维光锥有效透过率的理论分析

光锥的有效透过率不仅影响光锥与CCD的耦合效率,而且会影响到耦合器件的信噪比.本文主要从理论上讨论了影响光锥有效透过率性能的因素,从纤维光学元件的实际内部结构推导出了其实际有效填充率,从光线在光锥中的传输特征推导出了光线在光锥中传播时产生的衰减损耗,最后提出了提高光锥有效透过率的方法和途径.     

基于一代像增强器的高分辨率X射线相机

为了实现在较低剂量下获得较高的分辨率,研制了一款价格低廉的X射线CCD相机。该相机使用硫氧化钆作为转换屏、经一代像增强器增强后的图像通过光锥耦合到CCD相机上;为了提高系统的光传输效率,提出了将像增强器输出直面板或倒像器直接更换成光锥,其小端直接同CCD相机耦合的方案;通过灰度分析计算对比度曲线,拟合得出系统的本征空间分辨率为13 Lp/mm;通过拍摄实际景物,可以清晰地看到其内部的细节,显示出比较好的图像质量。     

D. CCD视频技术、等离子体诊断和脉冲辐射摄影

本文对CCD摄象技术、等离子体诊断和脉冲辐射摄影的国内外最新发展作了评述,并涉及到在高技术领域的应用。     

激光等离子体软x光辐射的时间分辨测量

采用透射光栅和软x光条纹相机测量了铜激光等离子体软x光发射的时间分辨光谱。通过比较时间分辨谱和时间积分光谱,从实验上考查了条纹相机在软x光区域的响应特性。文中也给出了激光等离子体软x光不同谱带及波长发射的时间过程。     

Coaxial fiber-optic chemical-sensing excitation-emission matrix fluorometer

Great reductions in the overall size and complexity of high throughput multichannel UV-visible fluorometers were achieved by coupling a compact optical fiber array to compact dispersive transmission optics. The coaxial configuration centers on the insertion of a silica/silica optical fiber into the hollow region of a UV-fused silica capillary waveguide. The outer core delivers the maximum power of the narrow wavelength region of the excitation spectrum created by coupling a xenon arc discharge lamp to a compact spectrometer. The molecular fluorescence resulting from the interaction of light emitted at the distal end of the hollow waveguide and the sample matrix is received and transmitted to a CCD via a compact dispersive grating-prism (grism) optical assembly. A linear array of the coaxial optical fibers permits a full excitation-emission matrix spectrum of the analyte matrix to be projected onto the face of the CCD. The in situ identification and monitoring of polycyclic aromatic hydrocarbons was carried out for the initial application testing for this prototype.     

High rep rate high performance plasma focus as a powerful radiationsource

Basic operational characteristics of the plasma focus are considered from design perspectives to develop powerful radiation sources. Using these ideas we have developed two compact plasma focus (CPF) devices operating in neon with high performance and high repetition rate capacity for use as an intense soft X-ray (SXR) source for microelectronics lithography. The NX1 is a four-module system with a peak current of 320 kA when the capacitor bank (7.8 μF×4) is charged to 14 kV. It produces 100 J of SXR per shot (4% wall plug efficiency) giving at 3 Hz, 300 W of average SXR power into 4π. The NX2 is also a four-module system. Each module uses a rail gap switching 12 capacitors each with a capacity of 0.6 μF. The NX2 operates with peak currents of 400 kA at 11.5 kV into water-cooled electrodes at repetition rates up to 16 Hz to produce 300 W SXR in burst durations of several minutes. SXR lithographs are taken from both machines to demonstrate that sufficient SXR flux is generated for an exposure with only 300 shots. In addition, flash electron lithographs are also obtained requiring only ten shots per exposure. Such high performance compact machines may be improved to yield over 1 kW of SXR, enabling sufficient exposure throughput to be of interest to the wafer industry. In deuterium the neutron yield could be over 10¹⁰ neutrons per second over prolonged bursts of minutes     

Influence of Kr doping on neon soft X-rays emission in fast miniature plasma focus device

An investigation on the possibility of enhancement of soft X-ray (SXR) (900–1600 eV) emission from a fast miniature plasma focus (FMPF) device of 235 J (at 14 kV) storage energy through doping of operating gas was performed. Neon (Ne), the operating gaseous medium, was doped with krypton (Kr) in different volumetric ratios at various operating pressures ranging from 2 to 14 mbar. The 1% Kr doping increased the average optimum SXR emission efficiency from 0.47% to 0.6% without enhancing the hard X-ray (HXR) (>1600 eV) emission. The Kr doping influenced the major pinching characteristics such as focusing efficiency and time to pinch with consequential effect on X-ray emissions. Synchronous operation of the 4 pseudo-spark gap (PSG) switches was mandatory for efficient discharge current delivery to the electrodes. A drastic improvement in the pinching efficiency was obtained with replacement of old and worn out PSG switches with the new ones. Optical imaging of current sheath dynamics was performed using gated ICCD camera to verify the normal operation of the device after the PSGs replacement. A numerical simulation analysis on the 2 cm long stainless steel tapered anode, used in this study, was done to predict the maximum SXR emission efficiency and the peak operating gas pressure. An analysis on the amount of SXR fluence generated at the source position and the proportion of it reaching the target position is also reported.