M.Sc. (Chemistry) / Please refer to full text to view abstract

The three-dimensional quadrupole ion trap (QIT) is an extraordinary device. It functions both as an ion store in which gaseous ions can be confined for a period of time and as a mass spectrometer of considerable mass range and variable mass resolution. Over the past few decades, it has evolved into a powerful tool for both research and routine analysis. The basic objective of this thesis is the development of a three-dimensional quadrupole ion trap with cylindrical symmetry in laminar approximation. The laminar construction allows hyperbolic geometry to be well approximated with minimal construction effort and also provides more access into the trap through interlaminar spaces without disruption of the field. The performance of the trap is examined in the mass selective trapping mode and mass-selective instability mode. Fourier detection is also done. Resolution of our instrument is limited by the external hardware. There is not good enough data quality and so not a good enough spectrum to predict its resolution accurately. A few changes to the instrumentation of the trap will improve the resolution.

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At the onset of this study, the work presented in Chapter 3 of this thesis was the primary focus. The work was motivated by JF Prins where he observed the formation of diamond layers on copper followed by C+ implantation into copper. This initial result suggested that it may be possible to generate single crystal diamond layers on single crystal copper. Subsequent efforts to reproduce this result failed. A unique end station was developed where a number of parameters could be altered during the implantation process. A series of carbon ion implantations were carried out on copper and copper-nickel (FCC) single crystals in this end station. The layers were characterised using initially Auger Electron Spectroscopy (AES), Low Energy Electron Diffraction (LEED) and later Raman Spectroscopy. During the early period of this study, the surface science equipment at the then Wits-Schonland Research Institute for Nuclear Sciences, was constantly giving problems. The time constraints on waiting for funds to be made available to repair the equipment, urged me to pursue alternative research endeavours and the results of this research is presented in chapter 4 and 5. The initial work will be investigated further in the future. Details of the end station are presented and the initial results of carbon layers generated in this end station are presented. In chapter 4, a study of C+ implantation into a type IIa (FCC single crystal) diamond using the cold implantation rapid annealing (CIRA) technique is reported. The Raman spectrum was recorded as a function of annealing temperature and C+ ion dose. De- fect peaks at 1450, 1498 and 1638 cm−1 appear in the Raman spectra, which have been previously considered to be unique to MeV implantation. The maximum energy of implantation used in this study was 170 keV. The peaks were monitored as a function of annealing temperature and ion dose. The annealing behaviour of the peaks were similar to those observed in the MeV implantation experiments. It is thus concluded that the defects that give rise to these peaks are related to the point-defect interac- tions that occur within the implantation regime and not to the implantation energy. 1 Understanding the nature of the defects that arise during the implantation annealing process, allows one to manipulate the implantation-annealing cycle, so as to generate defect structures that are useful in the fabrication of an active device in a diamond substrate. This is shown in chapter 5. A p-type (type IIb, FCC crystal) diamond was implanted with either carbon or phos- phorus ions using the cold implantation rapid annealing (CIRA) process. In each case, the energies and doses were chosen such that upon annealing, the implanted layer would act as an n-type electrode. The electroluminescence (EL) emitted from these carbon and phosphorus junctions, when biased in the forward direction, was compared as functions of annealing and diode temperatures. Typical luminescence bands such as those observed in cathodoluminescence (CL), in particular blue band A (2.90 eV) and green band (2.40 eV) were observed. Two bands centred around 2.06 and 4.0 eV were also observed for both the carbon and phosphorus junctions, while a band at 4.45 eV appeared only in the phosphorus implanted junction. This was the first time that the 4.45 eV band was observed in an electroluminescent junction.

by Cheung-Yin Tang. / Title also in Chinese. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1991. / Bibliography: leaves 83-84. / ACKNOWLEDGEMENTS --- p.i / TABLE OF CONTENTS --- p.ii / ABSTRACT --- p.iv / Chapter Chapter 1 - --- Introduction --- p.1 / Chapter 1.1 --- Structure --- p.2 / Chapter 1.1.1 --- Physical Structure --- p.2 / Chapter 1.1.2 --- Electronic Structure --- p.3 / Chapter 1.2 --- Hydrogenation --- p.9 / Chapter 1.2.1 --- Hydrogenation during film formation --- p.10 / Chapter 1.2.2 --- Posthydrogenation --- p.10 / Chapter 1.3 --- Doping of a-Si --- p.11 / Chapter 1.4 --- Previous Results and Applications --- p.13 / Chapter 1.4.1 --- Results --- p.13 / Chapter 1.4.2 --- Applications --- p.24 / Chapter Chapter 2 - --- Experimental Set-up and Techniques --- p.25 / Chapter 2.1 --- Sample Preparation --- p.25 / Chapter 2.1.1 --- Substrate cleaning procedure --- p.25 / Chapter 2.1.2 --- Deposition Method --- p.26 / Chapter 2.1.3 --- Annealing Method --- p.30 / Chapter 2.1.4 --- Hydrogenation Method --- p.31 / Chapter 2.1.5 --- Doping Method --- p.33 / Chapter 2.2 --- Measurements --- p.34 / Chapter 2.2.1 --- Dark Conductivity --- p.34 / Chapter 2.2.2 --- Room Temperature Photo-conductivity --- p.39 / Chapter 2.2.3 --- ESR (Electron Spin Resonance) --- p.39 / Chapter Chapter 3 - --- Results and Discussions --- p.41 / Chapter 3.1 --- Doping effect and posthydrogenation --- p.42 / Chapter 3.2 --- Annealing of the doped films --- p.44 / Chapter 3.3 --- Implantation at different dose levels --- p.46 / Chapter Chapter 4 - --- Conclusions --- p.82 / REFERENCES --- p.83 / APPENDIX --- p.85

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重離子核聚變是一種能源技術，它有可能為人類未來提供無限的潔淨能源。通過高能粒子撞擊含高濃度氘和氚的目標，從而產生強大的壓縮衝擊波，最終引發氘和氚核子聚變並釋放出巨大核能。在過去的幾十年裡，從離子注入到核反應控制技術，以至於整個重離子核聚變的基本概念都得到迅速的發展。其中一個重要的核聚變條件就是要求非常低的離子束的縱向發射度。 / 在論文的第一部分，我們研發了一種TSC 技術，它可以減少因粒子加速器的電壓變化而引起的縱向發射度增長。通過數值模擬，結果表明離子束的縱向發射度得到了約89% 的降低。如果把TSC 技術應用於重離子核聚變，離子束的縱向發射度就可以有效地被降低，從而促進更高效的核聚變反應。在論文的第二部分，我們以離子束的電流信號分析為基礎，研發了一種非干擾性的離子束能量測量方法。對於傳統干擾性的離子束能量測量，這種強調非干擾性的測量方法對未來重離子核聚變實驗以及高能粒子加速器研發都有實質的應用價值。在論文的第三部分，我們從NDCX 實驗數據分析中，證實離子束的電流信號能夠有效地揭示離子束微弱的能量變化。這個實驗結果相應肯定了論文第二部分的電流信號分析處理方法。在論文的第四部分，我們模擬在真實的NDCX 環境下測試TSC 技術。模擬結果表明TSC 技術可有效地把離子束的縱向發射度減少近89% ，從而證明了TSC 技術在實際應用中的能力。在論文的最後部分，我們在強電流離子束的一維波動行為中引入橫縱向稱合分析，解釋了一維波動行為與數值模擬結果之間的細小偏差。 / Heavy Ion Fusion (HIF) is a technology that has the potential to provide an unlimited source of clean energy for human future. HIF works by shooting at a capsule containing Deuterium and Tritium with energetic heavy ion beams such that the huge amount of kinetic energy carried by the ions is converted into strong compression shock waves. DT fuel is then compressed to form a high temperature and high density hotspot at the center of the capsule, thus igniting nuclear fusion between Deuterium and Tritium. Over the past few decades, the fundamental concepts of HIF had been tested in scaled ex¬periments from the source injection to the reaction chamber. To achieve the highest performance of ignition, ion beams with low longitudinal emittance is demanded. / In the first part of the thesis, we developed a novel Two-Step Correction (TSC) technique to reduce the growth of longitudinal emittance in an induc¬tion linac driver caused by variations in acceleration gap voltages. Through numerical studies, we achieved a reduction of longitudinal emittance by about 89% for high perveance ion beams. As a spinoff from the formalism developed in this study, we developed in the second part of the thesis a new non-invasive approach for the measurement of ion beam energy. The proposed diagnostics may have practical utility for future HIF experiments, particularly as higher energy accelerators are developed. It works by a generalized time-of-flight method, using two adjacent beam current signals to reconstruct the beam velocity profile. In the third part of the thesis, we verified that beam current signals are capable to reveal small beam energy variations by an NDCX-I experiment performed at Lawrence Berkeley National Laboratory. The result of this experiment confirms the formalism of the new non-invasive approach for the ion beam energy determination based on beam current signal analysis. In order to verify the effectiveness of TSC in real drivers, we proposed a new NDCX-I experiment in the fourth part of the thesis to test the limitations and performance of the correction technique in real environment. Through simulations with real driver features considered, a reduction of 89% of longitudinal emittance was observed, which confirms the ability of TSC in real applications. In the last part of the thesis, we revealed the limitation of the 1-D cold fluid model deployed in our analysis of space-charge waves for high perveance ion beams. We showed that inaccuracies are caused by transverse-longitudinal coupling which could be included in the wave equation for space-charge dominated beams. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Woo, Ka Ming = 抑制由粒子加速器的電壓變化所引起的縱向發射度 / 胡家明. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 153-156). / Abstracts also in Chinese. / Woo, Ka Ming = Yi zhi you li zi jia su qi de dian ya bian hua suo yin qi de zong xiang fa she du / Hu Jiaming. / Abstract --- p.ii / 概論 --- p.iv / Acknowledgement --- p.v / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Background --- p.4 / Chapter 2.1 --- Highlight --- p.4 / Chapter 2.2 --- Introduction to fusion energy --- p.4 / Chapter 2.3 --- Fusion technology --- p.5 / Chapter 2.3.1 --- Magnetic confinement fusions --- p.5 / Chapter 2.3.2 --- Inertial confinement fusions --- p.7 / Chapter 2.4 --- Inertia confinement fusion --- p.9 / Chapter 2.4.1 --- Principle of ICF --- p.9 / Chapter 2.4.2 --- Implosion dynamics --- p.11 / Chapter 2.4.3 --- Rayleigh-Taylor instability --- p.13 / Chapter 2.4.4 --- Fast ignition --- p.14 / Chapter 2.5 --- Heavy Ion Fusion --- p.16 / Chapter 2.5.1 --- Comparison between laser and heavy ion driven fusions --- p.16 / Chapter 2.5.2 --- Linear Induction Accelerator --- p.18 / Chapter 2.6 --- Operation of a HIF driver --- p.20 / Chapter 2.6.1 --- Source injection --- p.20 / Chapter 2.6.2 --- Transport of ion beams --- p.21 / Chapter 2.6.3 --- Acceleration of ion beams --- p.22 / Chapter 2.6.4 --- Neutralized drift longitudinal compression --- p.24 / Chapter 2.6.5 --- Target chamber --- p.25 / Chapter 2.7 --- Transverse beam dynamics --- p.26 / Chapter 2.7.1 --- Beam envelope equation --- p.26 / Chapter 2.7.2 --- Matched beams solutions --- p.29 / Chapter 2.8 --- Longitudinal beam dynamics --- p.30 / Chapter 2.8.1 --- Cold plasma model --- p.30 / Chapter 2.8.2 --- Self longitudinal electric field --- p.32 / Chapter 2.8.3 --- Longitudinal emittance --- p.34 / Chapter 2.9 --- Intense ion beam simulation --- p.35 / Chapter 2.9.1 --- Particle-In-Cell method --- p.35 / Chapter 2.9.2 --- WARP code --- p.36 / Chapter 2.10 --- Conclusion --- p.37 / Chapter 3 --- Techniques for correcting velocity and density fluctuations of ion beams --- p.39 / Chapter 3.1 --- Highlight --- p.39 / Chapter 3.2 --- The quest for short-pulse length ion beams --- p.40 / Chapter 3.2.1 --- Applications of short-pulse ion beams --- p.40 / Chapter 3.2.2 --- Consequence of the growth of longitudinal emittance --- p.41 / Chapter 3.3 --- Effect of gap voltage variation on εzn --- p.42 / Chapter 3.3.1 --- Description of simulation scenario --- p.42 / Chapter 3.3.2 --- The coasting of an unperturbed ion beam and a velocitytilt beam --- p.43 / Chapter 3.3.3 --- Effect of many constant voltage gaps --- p.44 / Chapter 3.3.4 --- Effect of non-uniform voltage gap --- p.46 / Chapter 3.4 --- One-step correction --- p.48 / Chapter 3.4.1 --- Criteria for the one-step correction --- p.52 / Chapter 3.4.2 --- Space-charge dominated beams --- p.55 / Chapter 3.5 --- Two-step correction --- p.56 / Chapter 3.5.1 --- Principle of two-step correction --- p.56 / Chapter 3.5.2 --- Result of two-step correction --- p.59 / Chapter 3.6 --- Conclusion --- p.62 / Chapter 4 --- A new non-invasive approach for the measurement of ion beam energy --- p.63 / Chapter 4.1 --- Highlight --- p.63 / Chapter 4.2 --- Introduction --- p.64 / Chapter 4.3 --- Derivation of the ion beam energy based on two current signals --- p.65 / Chapter 4.3.1 --- Obtaining the time evolution of the beam current --- p.65 / Chapter 4.3.2 --- Deriving the beam energy profile --- p.67 / Chapter 4.3.3 --- Obtaining the average velocity --- p.70 / Chapter 4.4 --- Checking the beam energy profile with 3-D PIC simulations --- p.72 / Chapter 4.4.1 --- Determination of the average velocity --- p.73 / Chapter 4.4.2 --- Computation of the beam energy profile --- p.74 / Chapter 4.5 --- Signal magnification --- p.74 / Chapter 4.6 --- Error propagations --- p.77 / Chapter 4.7 --- Conclusion --- p.81 / Chapter 5 --- Experimental verification of the beam current signal amplification --- p.83 / Chapter 5.1 --- Highlight --- p.83 / Chapter 5.2 --- Introduction to NDCX-I --- p.84 / Chapter 5.3 --- Design of the NDCX-I experiment --- p.88 / Chapter 5.4 --- Voltage profiles applied at the source plate --- p.90 / Chapter 5.4.1 --- Marx voltage profile --- p.90 / Chapter 5.4.2 --- Voltage modulation --- p.91 / Chapter 5.5 --- Signal amplification of beam currents measured at the Faraday cup --- p.92 / Chapter 5.6 --- Modeling of the space-charge wave propagation --- p.94 / Chapter 5.6.1 --- Solving for the line-charge density profile at the source plate --- p.94 / Chapter 5.6.2 --- Procedure of space-charge wave modeling --- p.99 / Chapter 5.7 --- Conclusion --- p.101 / Chapter 6 --- Implementation of Two-Step Correction in NDCX-I --- p.103 / Chapter 6.1 --- Highlight --- p.103 / Chapter 6.2 --- Application of the current signal analysis to the Two-Step Correction --- p.104 / Chapter 6.3 --- Proposal of the new NDCX-I experiment --- p.107 / Chapter 6.3.1 --- Design of the beamline --- p.107 / Chapter 6.3.2 --- Description of the simulation scenario --- p.110 / Chapter 6.3.3 --- Result of the Two-Step Correction simulation --- p.114 / Chapter 6.4 --- Conclusion --- p.126 / Chapter 7 --- Transverse-Longitudinal coupling in the wave equation --- p.128 / Chapter 7.1 --- Highlight --- p.128 / Chapter 7.2 --- Phenomenological study of residue --- p.129 / Chapter 7.2.1 --- Description of the simulation scenario --- p.129 / Chapter 7.2.2 --- Modeling of the velocity wave --- p.131 / Chapter 7.2.3 --- Phenomenon of residue --- p.133 / Chapter 7.3 --- Review of the space-charge wave equation --- p.141 / Chapter 7.3.1 --- Fluid description of ion beams --- p.141 / Chapter 7.3.2 --- Beam envelope perturbation --- p.145 / Chapter 7.4 --- Conclusion --- p.149 / Chapter 8 --- Conclusion --- p.150 / Bibliography --- p.153