球面弯晶成像的优化设计及实验测试

为满足"神光Ⅱ"升级激光装置实验的激光等离子体高空间分辨和窄带宽的精密成像诊断需求,本文研究球面弯晶单色成像技术,并对其进行优化设计及实验验证。首先,使用光线追迹方法分析了成像像距、布拉格角、背光源尺寸等成像系统参数对球面弯晶成像性能的影响,分析了设计参数的变化对成像空间分辨能力的影响,并在X射线管上开展了测试验证实验。研究结果表明:二维成像时,在等分辨成像像距处可以获得较好的成像结果,增大布拉格角可以抑制像差进而提高成像质量,更小的背光源尺寸也有助于提高成像的空间分辨率。测试实验获得了清晰的网格背光成像,成像结果与预期相符,空间分辨率优于14μm。这一工作有助于球面弯晶成像系统的优化设计及其在激光等离子体精密诊断中的应用。     

球面弯曲晶体在X射线背光成像的应用

基于X射线布喇格衍射理论,研制了球面弯曲晶体分析器,用于研究和诊断惯性约束聚变的聚爆靶等离子体的形状、分布及稳定性.分析器的核心器件是石英球面弯晶,弯曲晶体半径为143.3 mm.首次利用石英球面弯曲晶体进行了单色X射线背光成像实验.采用接收面积为40 mm×30 mm的磷屏成像板作为接收装置,得到了清晰的铬靶单色X射...     

High resolution absorption spectroscopy of exploding wire plasmas using an x-pinch x-ray source and spherically bent crystal

We present here the use of absorption spectroscopy of the continuum radiation from x-pinch-produced point x-ray sources as a diagnostic to investigate the properties of aluminum plasmas created by pulsed power machines. This technique is being developed to determine the charge state, temperature, and density as a function of time and space under conditions that are inaccessible to x-ray emission spectroscopic diagnostics. The apparatus and its characterization are described, and the spectrometer dispersion, magnification, and resolution are calculated and compared with experimental results. Spectral resolution of about 5000 and spatial resolution of about 20 μm are demonstrated. This spectral resolution is the highest available to date in an absorption experiment. The beneficial properties of the x-pinch x-ray source as the backlighter for this diagnostic are the small source size (<5 μm), smooth continuum radiation, and short pulse duration (<0.1 ns). Results from a closely spaced (1 mm) exploding wire pair are shown and the general features are discussed.     

Accurate miscut angle determination for spherically bent Bragg crystals

Spherically bent crystals are used as analyzers in high-resolution spectroscopy, in particular, in low count-rate applications such as exotic-atom research. The focal conditions are determined not only by the bending radius and the Bragg angle but also by the crystal cut angle between its surface and the reflecting crystal planes, along with their orientation with respect to the direction of dispersion. We describe a simple but precise method for measuring the cut angle and its orientation for mounted spherically bent crystals, by combining x-ray diffraction and laser optical alignment, which can be easily performed with standard x-ray laboratory equipment.     

Calibration of an imaging crystal spectrometer for low x-ray energies

An x-ray imaging crystal spectrometer was designed for the Hanbit magnetic mirror device to observe spectra of heliumlike neon at 13.4474 A. The spectrometer consists of a spherically bent mica crystal and an x-ray sensitive vacuum charge coupled device camera. This spectrometer can provide spatially resolved spectra, making it possible to obtain profiles of the ion charge state distribution from line ratios and profiles of the plasma rotation velocity from Doppler shift measurements. The paper describes measurements of spectral resolution of this instrument for low x-ray energies.     

The first experimental results from x-ray imaging crystal spectrometer for KSTAR

The x-ray imaging crystal spectrometer (XICS) for the Korea Superconducting Tokamak Advanced Research has been first applied for the experimental campaign in 2009. The XICS was designed to provide measurements of the profiles of the ion and electron temperatures from the heliumlike argon (Ar XVII) spectra. The basic functions of the XICS are properly working although some satellites lines are not well matched with the expected theoretical values. The initial experimental results from the XICS are briefly described.     

一种新型曲面晶体成像系统的研制

为了对诊断目标进行瞬态辐射成像,提出了研制X射线聚焦成像系统,主要器件为一各向同性的X射线点光源及超环面弯曲晶体成像器.X射线照射至被成像物体后再投射到超环面晶体,经该凹面晶体聚焦后在X射线探测器表面成像.讨论了超环面晶体在布拉格几何结构中的聚焦成像特性,提出利用X射线源进行二维优化成像的适用条件.利用模拟软件对网格物体进行仿真成像,研究像距及光源尺寸对成像空间分辨力的影响,并据此确定了实验参量.设计的超环面弯晶采用云母材料,子午面曲率半径为290 mm,弧矢面曲率半径为190 mm.利用该系统进行了X射线背光成像实验,实验结果表明:系统的成像空间分辨力最高可达到34μm,能够满足聚爆辐射成像的要求;在光源尺寸较大时像距变化对成像效果有明显影响.     

Objectives and layout of a high-resolution x-ray imaging crystal spectrometer for the large helical device

A high-resolution x-ray imaging crystal spectrometer, whose concept was tested on NSTX and Alcator C-Mod, is being designed for the large helical device (LHD). This instrument will record spatially resolved spectra of helium-like Ar(16+) and will provide ion temperature profiles with spatial and temporal resolutions of <2?cm and ≥10?ms, respectively. The spectrometer layout and instrumental features are largely determined by the magnetic field structure of LHD. The stellarator equilibrium reconstruction codes, STELLOPT and PIES, will be used for the tomographic inversion of the spectral data.     

Asymmetrically cut crystal pair as x-ray magnifier for imaging at high intensity laser facilities

The potential of an x-ray magnifier prepared from a pair of asymmetrically cut crystals is studied to explore high energy x-ray imaging capabilities at high intensity laser facilities. OMEGA-EP and NIF when irradiating mid and high Z targets can be a source of high-energy x-rays whose production mechanisms and use as backlighters are a subject of active research. This paper studies the properties and potential of existing asymmetric cut crystal pairs from the National Institute of Standards and Technology (NIST) built in a new enclosure for imaging x-ray sources. The technique of the x-ray magnifier has been described previously. This new approach is aimed to find a design that could be used at laser facilities by magnifying the x-ray source into a screen far away from the target chamber center, with fixed magnification defined by the crystals' lattice spacing and the asymmetry angles. The magnified image is monochromatic and the imaging wavelength is set by crystal asymmetry and incidence angles. First laboratory results are presented and discussed.     

用于测量激光等离子体X射线的椭圆弯晶谱仪

研制了一种椭圆弯晶谱仪用于测量0.44～0.81 nm激光等离子体X射线光谱.该谱仪采用X射线CCD作探测器,用PET(2d＝0.874 nm)晶体作色散和聚焦元件,将晶体弯曲并粘贴在离心率和焦距分别为0.9586和1350 mm的椭圆形不锈钢基底上.对该谱仪在"星光Ⅱ"激光装置上进行了打靶实验,实验结果表明其光谱分辨率接近1000.     

Time resolving bent crystal spectrometer for tokamak plasma diagnostics

A high-throughput high-resolution curved crystal spectrometer for measurements in the soft X-ray range on fusion magnetic devices is described. The spectrometer uses a large useful area (8 × 5 cm²) quartz lamina bent at a curvature radius 385 cm long as the dispersing element. The detector is a one-dimensional space resolving multiwire proportional counter. The spectral resolving power is R = 18 000, permitting to obtain adequate ion temperature measurements, down to 700 eV, from the Doppler broadening of resonance lines of highly ionized metallic impurities.     

Data acquisition system for an advanced x-ray imaging crystal spectrometer using a segmented position-sensitive detector

A versatile time-to-digital converter based data acquisition system for a segmented position-sensitive detector has been developed. This data acquisition system was successfully demonstrated to a two-segment position-sensitive detector. The data acquisition system will be developed further to support multisegmented position-sensitive detector to improve the photon count rate capability of the advanced x-ray imaging crystal spectrometer system.     

Development of advanced x-ray imaging crystal spectrometer utilizing a large area segmented proportional counter for KSTAR

An advanced x-ray imaging crystal spectrometer (XICS) for KSTAR tokamak has been developed by utilizing a segmented two dimensional (2D) position-sensitive multiwire proportional counter. The XICS for the KSTAR tokamak provides time-resolved measurements of the radial ion and electron temperature profiles, toroidal plasma rotation velocity, and ionization equilibrium. The segmented 2D detector with delay-line readout and supporting electronics has been adopted to improve the photon count rate capability. The current fabrication status of the XICS for the KSTAR tokamak and the first performance test results of the prototype segmented 2D detector are presented.     

紫外临边成像光谱仪CCD电路系统的设计

提出一种用于紫外临边成像光谱仪模数分离成像电路的系统设计方案,该方案避免了CCD模拟输出信号的板间传输和数字信号对模拟信号的干扰,使CCD信号处理电路的噪声水平达到了模拟前端数据手册中给出的2 LSB的性能指标.考虑CCD57-10 BI AIMO没有抗溢出结构,在饱和之前会发生电荷溢出现象,提出了临界溢出电子数的概念...     

Electro-magnetically enforced rotary barrel finishing for fabricating spherically contoured quartz crystal blanks

Spherically contoured AT-cut rectangular quartz crystal resonators have been fabricated by electro-magnetically enforced rotary barrel finishing system. Shape and frequency responses of the fabricated blanks have also been measured and compared with those of the blanks fabricated without using the electro-magnets. In previous work by the authors, the fixed abrasive method, in which abrasive papers are used instead of powder abrasives, was introduced as a new rotary barrel finishing method for fabricating the spherically contoured rectangular quartz crystal blanks. By adopting the fixed abrasive method, accurate shape transferring, dustless clean working environment, and short turnaround time has been realized. In this paper, in order to further shorten the process time, electro-magnets are used for generating additional machining pressure. As a result, the process time required for complete shape transferring has been decreased to 67% of the turnaround time obtained by previous work.     

凸面光栅成像光谱仪的干涉法装调

研究了Offner凸面光栅成像光谱仪同心分光系统的装调方法.将双光束干涉基本原理与同心光学系统基本特点相结合,提出了适用于Offner凸面光栅成像光谱仪的干涉装调法.该方法首先对凸面光栅成像光谱仪同心光学系统的两个凹球面反射镜进行同心装调,由于单个球面反射镜的离焦量难以调整至零,故引入相对离焦使两个反射镜的离焦量相等,...     

Optimizing the bent crystal parameters for high-efficiency beam extraction and collimation in circular accelerators

The efficiency of the extraction and collimation systems in circular accelerators with the use of the channeling effect in a bent crystal is determined. The dependences of the extraction efficiency on the geometrical parameters of the crystal (its length, thickness, and bending angle), the azimuthal location of the system components, and the offset of the septum or scraper are presented. The influence of crystal imperfections (amorphous layers, misorientation, and torsion) on the efficiency of the systems is considered, and their tolerances are proposed. It is shown that an extraction efficiency of >95% can be attained over a wide energy range from 2 GeV to 7 TeV by optimizing the crystal parameters and the positions of the system components.     

K-shell emission x-ray imaging of Z-pinch plasmas with a pinhole and a logarithmic spiral crystal

An in-chamber, mini x-ray imaging instrument employs a pinhole and a logarithmic spiral crystal has been developed for obtaining K-shell line images of the imploding aluminum wire array on the "Yang" accelerator. The logarithmic spiral crystal acts as a monochromator and a non-dispersive mirror that reflects the pinhole image to a x-ray film detector with a very narrow photon energy bandwidth (<1 eV, mainly determined by the width of rocking curve of the crystal). Two imaging configurations with the use of Quartz (10 ?10) crystal and Mica (002) crystal are designed, respectively, to image the Al Ly(α2) line (1727.7 eV) emission and Al He(α) intercombination line (1588.3 eV) emission. The primary experimental data corresponding to these two configurations are presented and discussed.     

热管理技术在紫外成像光谱仪热控制中的应用

研究了紫外成像光谱仪热控制的特点,指出采用常规热设计理念对紫外成像光谱仪散热容易造成散热面面积大、主动加热功耗高等问题。基于热管理技术,提出采用统一收集和综合管理仪器热源产生热量的方法来解决紫外成像光谱仪的热控制问题。对紫外成像光谱仪的热设计验证试验表明:低温工况下整机平均温度变化为18～20℃,最大轴向温差变化为1.0～2.4℃;高温工况下整机平均温度变化为18～24.5℃,最大轴向温差变化为1.2～3.3℃;均满足热控指标要求。结果显示:采用热管理技术综合收集和管理热量能够提高能量利用率、有效降低热控系统规模。提出的方法对其它空间光学遥感器的热控制具有一定参考意义。     

Layout and results from the initial operation of the high-resolution x-ray imaging crystal spectrometer on the Large Helical Device

First results of ion and electron temperature profile measurements from the x-ray imaging crystal spectrometer (XICS) diagnostic on the Large Helical Device (LHD) are presented. This diagnostic system has been operational since the beginning of the 2011 LHD experimental campaign and is the first application of the XICS diagnostic technique to helical plasma geometry. The XICS diagnostic provides measurements of ion and electron temperature profiles in LHD with a spatial resolution of 2 cm and a maximum time resolution of 5 ms (typically 20 ms). Ion temperature profiles from the XICS diagnostic are possible under conditions where charge exchange recombination spectroscopy (CXRS) is not possible (high density) or is perturbative to the plasma (low density or radio frequency heated plasmas). Measurements are made by using a spherically bent crystal to provide a spectrally resolved 1D image of the plasma from line integrated emission of helium-like Ar(16 +). The final hardware design and configuration are detailed along with the calibration procedures. Line-integrated ion and electron temperature measurements are presented, and the measurement accuracy is discussed. Finally central temperature measurements from the XICS system are compared to measurements from the Thomson scattering and CXRS systems, showing excellent agreement.