【作者】 彭海波；

【导师】 王铁山；

【作者基本信息】 兰州大学 ， 粒子物理与原子核物理， 2009， 博士

【摘要】 高电荷态离子（Highly Charged Ion HCI）是核电荷数较高同时外壳层电子被大量剥离的离子。高电荷态离子的研究对天体物理、量子色动力学、原子的精细结构和原子质量测量等研究领域都有着重要的意义。由于高电荷态离子所携带的巨大势能，高电荷态离子也有望成为表面分析和表面改性的新工具。在医学应用方面，高电荷态离子易于被加速的特性，使其成为重离子治癌的首选离子。本文介绍了高电荷态离子的特性，产生高电荷态离子的离子源以及国内外对高电荷态离子与固体相互作用研究的主要方向和国内外在实验和理论研究的动态；描述了ECR （Electron Cyclotron Resonance）源和EBIT （ElectronBeam Ion Trap）的工作原理，详细介绍了高电荷态离子在固体表面溅射实验的样品制备、碰撞靶室以及束流光学系统；同时还重点介绍了电子束离子阱和X射线探测系统。简单介绍了Wien filter的工作原理，详细描述了Wien filter的测试过程以及相关的控制解谱软件。在实验方面，本文研究了电子束离子阱的工作参数对离子源输出和工作稳定性的影响。实验证实了电子束的密度对电子能量的敏感性。因此电子的能量不仅会影响到暗电流大小，而且可以直接影响到离子的输出，而真空度对束流输出的影响取决于离子的电荷态。当阱区的气压升高时，总的输出电流增大，低电荷态离子的流强增大，高电荷态离子流强；当阱区气压降低时，总的输出电流减少，低电荷态离子流强减少，高电荷态离子流强增大。关于势阱深度对输出的影响，在实验当中当势阱深度为20V，在恒流模式下高电荷态离子的输出最大。引出电压对束流的影响不明显，最佳的引出电压为4keV。同时，我们测量了高电荷态离子在电子束离子阱中的X射线谱和引出束流谱。利用双电子重组的过程，鉴别不同电荷态的Kr离子。得到了在势阱开启和关闭条件下势阱中的电荷态分布，进一步得到了特定电荷态（28＜q＜32）的Kr离子在势阱关闭后的演化行为。分析了高电荷态离子在EBIT势阱中的演化行为。在溅射实验研究方面，我们使用不同能量的高电荷态Ar^q+、Pb^q+离子入射金、银、铜、铌、钨、云母、硅和SiO₂材料表面，并用微通道板测量了溅射产额的角分布；得到了溅射产额随入射离子的电荷态和动能变化的关系曲线。测量结果表明：当离子入射绝缘体和导体表面时，溅射产额随着入射角增大而减少，在晶体硅表面溅射产额有明显的沟道效应。在Ar^q+离子Pb^q+离子入射材料表面随着入射离子动能的增加呈现出不同的趋势。当Ar离子以E（96 keV＜E＜320 keV）动能入射材料表面时，随着动能增加溅射产额减少；当Pb离子以E（196 keV＜E＜720 keV）动能入射材料表面时，随着入射离子能量增加，溅射产额先增加后减少。对于不同电荷态Ar^q+/Pb^q+离子入射材料表面，溅射产额随着势能增加而增加。基于上述溅射实验，我们提出了动能势能共同作用模型。该模型的基本思想是溅射分成两部分。一部分是动能势能相互作用的结果，它是入射角的函数且正比于入射离子在材料表面的核能损，与材料的表面结合能成反比；另一部分是势能溅射结果，它与离子有效电荷态的三次方成正比。比较试验结果和理论模拟的结果，发现在一定程度上它们符合的较好。根据模型结果溅射产额的角分布可以用经验公式Y=AtanBθ++C来描述，此公式与实验符合的较好。该模型能够较好地解释溅射结果，同时也可以较好地解释其他小组的相关实验结果。更多还原

【Abstract】 Highly Charged Ion （HCI） is an ion which has high Z value and is peeled offmost of bound electrons. The study of HCI is interested in astrophysics, quantumchromo dynamics, hyperfine atomic structure and measurement of atomic mass.The HCI is also respected to be a powerful tool for surface modification andsurface analysis. In addition, HCI is the favorite choice in medical application ofheavy-ion cancer therapy because HCI is easy to be accelerated.In this paper, the characteristics and sources of the HCI were introduced. Thestudies of the interaction of HCI with solid surface which had done by othersgroups and experimental, theoretical results were presented briefly. The operatingprinciples of the ECR source and EBIT （electron beam ion trap） were described.The experiment of sputtering induced by impact of HCIs on solid surface wasdescribed in detail. As well as, the chamber, preparation of the targets and targetholder were introduced. The EBIT system and X ray detector were presented. Theoperating principle of the Wien filter was roughly introduced and the testexperiment, control software and analyzing software were introduced in detail.It was studied that the parameters of the EBIT influenced on the intensity ofthe extracted ion beam and the stability of the EBIT. It was indicated the electrondensity was sensitive to the electron energy, which had influence not only on thedark current but also on the intensity of the extracted ion beam. The pressureinfluence on the specific ion beam is depended on the charge state of the ions. Forthe highly charged ions, the higher pressure was, the higher intensity of extractedion beam would be; for the lower charged ions, the case was opposite. When thedepth of the trap was 20V, the output of the ion beam was up to the maximum inleak mode. It was no clear how the extracted potential voltage affected on theoutput of the ion beam. The optimal value of the extraction voltage equals 4 ke V.It was measured the X ray spectra of the HCIs which were trapped in theEBIT as well as the extraction spectra of HCIs. The specific charged ions wereidentified by X ray form the dielectronic recombination process. The charge state distribution in the drift tube was obtained with opened and closed trap. Furtherthe evolution of the Kr^q+ （28<q<32） ions was measured in pulsed mode. Theevolution of the HCI in EBIT was studied.Ar^q+ and Pb^q+ ions with different kinetic energies bombarded on the solid surfacesof Au, Ag, Nb, Cu, mica, W, silicon and glass and theangular distributions of sputtering were measured by a multi-channel plate. Therelation between sputtering yield and potential energy, kinetic energy wasintroduced. The experimental results showed that the sputtering yield wasincreased as the incident angle was grown for the impact of the HCIs on the metaland insulator surface and there was channeling effect during the HCIs bombardedon the silicon surface. The different trends were shown with impact of differentenergies Ar¹⁶⁺ and Pb³⁶⁺ on the solid surface. The sputtering yield increased as thekinetic energy of the projectile grown for the bombardment of Ar¹⁶⁺ ions withenergy from 96 keV to 320 keV. However in case of Pb³⁶⁺ with kinetic energyfrom 196 keV to 720 keV, the trend was not clear. The sputtering yield increasedwith the increasing of potential energy of the projectile during Ar^q+/Pb ^q+bombarded on the different surfaces. The cooperation sputtering model wasproposed to explain the results. The basic ideal of the model is the sputteringshould be separated into two portions. The one is kinetic sputtering yield, whichwas function of the incident angle. The kinetic sputtering yield is proportional tothe nuclear stopping power and inverse proportional to the bind energy of thesurface. Another was potential sputtering yield, which was proportional to theeffect charge state of the ion cubed. The experimental sputtering yield was fittedby an empirical formula of Y=Atan^Bθ+C. The formula is fitted well with themodel. The model was in good agreement with our results as well as the resultsfrom other groups.更多还原