【作者】 杨洋；

【导师】 邹亚明；

【作者基本信息】 复旦大学 ， 原子与分子物理， 2011， 博士

【摘要】 等离子体广泛存在于宇宙空间中,对等离子体的研究不仅可以实现对遥远星体的演化的探索,也可以为当今高新技术的发展提供重要的基础支撑。等离子体研究的一个重要动力就是来源于对解决能源问题的迫切需要。托卡马克装置是实现受控核聚变最有希望的途径之一。而其中的等离子体的磁场强度是影响其能量输运和约束时间的关键因素。通过先进的电子束离子阱(EBIT)装置来分解研究等离子体是当今新兴的等离子体研究方向。本工作通过大范围的理论计算,探讨了在EBIT中通过磁场诱导跃迁来诊断等离子体磁场的可行性,并且为实现未来的实验研究建设了相应的观测平台以及分析手段。具体内容包括：一.系统研究了等电子系列类氖离子第一激发态2p53s 1,3P四条能级的激发能,及它们到基态和它们之间各跃迁的跃迁几率。重点研究了在外加磁场的参与下磁场诱导跃迁(B:2s22p61S0-2s22p53s3P0的跃迁几率和该激发能级的退激分支比,以及通过“碰撞辐射模型”方法计算了该跃迁和E1跃迁1S0-1P1的线强(及线强比)随外加磁场及入射电子能量和电子密度的演化关系,以及这些关系在等电子系列中的演化。通过研究找出了可以在实验中进行观测的离子元素。同时预测了这些元素相应跃迁光子的能量范围和谱线强度,以及所需要的实验环境。二.根据理论计算的结果,建设了适合观测磁场诱导跃迁的平焦场谱仪系统以及校刻手段。在精密的变栅距光栅谱仪的搭建中,发展了激光和准直望远镜双向对中装配的方法。在谱仪的能量校刻中,发展了新的校刻拟合方程,实现了单次的全谱范围校刻,成功地校刻了离线测试光源的所有谱线。并且成功实现了在线的磁场诱导跃迁相关谱线的观测和校刻,得到了可信的结果。三.由于磁场诱导跃迁的弱光信号对探测系统的信噪比要求很高,对使用CCD(电荷耦合器件)探测极弱光谱的情况,本工作研究了CCD的探测原理,根据其具有的能量分辨能力,开发了一套高效的弱光子信号分离算法,并且编制了相应的自动化程序。通过该程序的处理,光谱的信噪比得到显著的提高,同时在不对谱线造成畸变的情况下,成功地抑制了多种类型的噪声。四.在基于EBIT的磁场诱导跃迁研究等精密光谱学研究中,亟需对电子束的形态有充分的了解以推算电子密度等重要参数,为此本工作在上海EBIT上建立了电子束X射线狭缝成像系统。为获得高精度的测量,分析了成像过程中包括卷积效应和像素化等过程,并且深入研究了先进的非线性多参数函数的Levenberg-Marquardt (LM)拟合算法,使用LM方法编制了基于积分高斯分布的狭缝成像去卷积自动数据处理程序。通过数据分析,得到了在不同状态下EBIT电子束的束径和束流密度以及电子密度。五.在EBIT多种光谱的分析工作中,基于Visual Studio C++ MFC开发了适用于多种光谱的多功能光谱显示和处理软件’"Spectrer",大大方便了对各类实验光谱的处理。更多还原

【Abstract】 The study of plasmas gives us the opportunity to explore the evolution of the stars in the universe, and at the same time gives strong support to developments in modern high-technology. The urgent demand of new energy sources has boosted the study of plasmas which could possibly achieve controlled fusion. The Tokomak device is an approach in which great hope is placed to bring final success to the quest for fusion power. To achieve stable plasma, in which energy producing fusion can occur in a Tokomak, the magnetic field is a crucial parameter for the energy transportation and the trapping time. The newly developing techniques to study plasmas with Electron Beam Ion Traps (EBIT) are becoming powerful methods for decomposing the many complex atomic physics processes occurring in fusion plasmas. Part of this thesis is devoted to theoretical studies done for a broad region of elements to discuss the feasibility of magnetic field diagnostics in plasma by observing magnetic field induced transition in an EBIT. Also discussed in this thesis is the development of a spectrometer system covering a good wavelength for studies of magnetic sensitive lines, along with special analysis methods for weak spectral lines region. Details of this work contained in the thesis are as below:1. A systematic calculation along the Ne-like sequence of the transition rates between the first four excited levels and the ground level, i.e.2s22p61S0-2s22p53s 1,3P, is presented. The transition rate of the magnetic field induced transition,<B, between the 2s22p61S0-2s22p53s 3P0 are calculated, following the investigation of the branching ratio of the transition B and transition M1 (Magnetic dipole transition) from 3P0, and the relation between the strength of the external magnetic field and the intensity ratio of the transition E1 (Electric dipole transition) from 1P1 and B are also presented. Using a "Collision Radiation Model", calculations of the line-intensities of B and E1 transitions are applied to study the relationships of line-intensities, magnetic field, energy and density of the incidence electron beam. Using these calculations, we discussed the selection of elements for experimental observations using an EBIT and forecast the photon energy and spectral line intensity of the possible magnetic field induced transitions and the environments that the possible experiments require.2. A spectral system for observing photons from magnetic induced transition has been developed based on flat field grating techniques. This design of this system follows the forecasted photon energy region for magnetic induced transition in a number of astrophysical and fusion diagnostic important elements. This work also developed a method of alignment with using both a laser and a telescope independently for the very sensitive optical system. Also a new calibration function is introduced for the flat field spectrometer to achieve a whole spectrum calibration using only a few spectral calibration lines.3. As it is likely that magnetic induced transitions will involve the study of very weak photon signals from the Shanghai EBIT, an algorithm for analyzing weak signals, i.e. where the signal/noise ratio is not high, has been developed, based on the energy resolution ability of a CCD detector. A program based on this algorithm was made for analyzing spectra from a flat crystal spectrometer, which normally also gives a very weak photon signal. The program is shown to achieve a significant improvement in the signal noise ratio, and can eliminate different kinds of noise while making no distortion to the spectral line.4. The study of the spectroscopy of magnetic field induced transitions in an EBIT requires observations of detailed shape and form of the electron beam. A slit imaging system for X-rays has been developed and installed at the shanghai EBIT and this is also presented in this work. The convolution effects caused by the finite slit width and the pixelation effects of the CCD to the imaging have been studied in great detail. A Levenberg-Marquardt algorithm has been introduced to develope a computer program which can generate a fit of the integral of the Gaussian function, which represent the convolution process. This in turn enables the deconvolution of the image and leads to a high precision measurement of the electron beam density. A series of beam widths and electron beam densities under different operation conditions of the Shanghai EBIT, i.e. beam energies and currents is presented based on the analysis results from the program.5. A software named "Spectrer" which has a multiple of functions for display and analysis of the spectra from different spectrometers has also been developed in this work. This software adds much to the daily work and analysis of spectroscopy and should help provide many interesting results in atomic stricture in the future.更多还原