| 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. |
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