Study on charge equilibration time of highly charged ions in carbon foils

Charge state distribution of 0.8MeV/u uranium ions after transmission through a thin carbon foil has been studied. It is observed that the charge state distribution is equilibrated after the uranium ions have passed through a 15μg/cm^2 carbon foil. The equilibrated average charge state is 33.72 and the charge equilibration time of uranium ions in carbon foil is less than 5.4fs.     

高电荷态离子40Arq+与Si表面作用中的电子发射产额

报道了在兰州重离子加速器国家实验室电子回旋共振离子源原子物理实验平台上，用高电荷态⁴⁰Ar^q+(1≤q≤12)离子作用于半导体Si固体表面时的电子发射产额实验测量.实验中，通过改变炮弹离子的电荷态和引出电压选取其不同的势能和动能，系统地研究了入射离子势能沉积和与其在固体中的电子能损对表面电子发射产额的贡献.结果表明，作为引起表面电子发射的两个主要因素，单离子的电子发射产额与炮弹离子在固体表面的势能沉积和电子能损都有近似的正比关系.     

电子束离子阱中高价态离子演化过程的数值模拟

讨论了电子束离子阱(EBIT)中决定高价态离子演化过程的主要物理机制.对EBIT中高价态离 子的演化过程进行了详细的数值计算并与实验进行了比较.讨论了EBIT各种不同的运行参数 对平衡时高价态离子相对丰度和温度的影响. 关键词： 电子束离子阱 高价态离子 数值模拟     

Resonant electron impact excitation of highly charged Fe ions studied with a compact electron beam ion trap

We present extreme ultraviolet spectra of 3s3p–3s3d transitions in Fe¹⁴⁺ observed with a compact electron beam ion trap. The contributions of indirect excitation via a metastable state and resonant excitation are studied by observing the electron energy dependence of the spectra for the energy range of 60–210 eV. The results indicate that the 3s3d ¹D₂ level is directly excited from the 3s² ground state whereas the 3s3d ³D₃ level has a large contribution of the indirect excitation via the 3s3p ³P₂ metastable state. Comparisons with the theoretical excitation cross sections including MNn resonant excitations show good qualitative agreement with the experimental results for the electron energy dependent features.     

Production of highly charged argon ions from a room temperature electron beam ion trap

In this work.highly charged ions have been extracted from the advanced Electron Beam Ion Source (EBIS-A) developed in a scientific cooperation between the Dresden University of Technology and the DREEBIT GmbH Dresden.The charge state distributions of ions extracted from the EBIS-A are measured in and extracted in the leaky mode.3×105 Ar18+ ions per pulse are extracted in the pulse mode.The ion charge state distribution is a function of the ionization time.     

The charge exchange of slow highly charged ions at surfaces unraveled with freestanding 2D materials

The property of a variable charge state makes ions unique to other types of radiation a material surface can be exposed to. As a consequence of charge exchange between ions and surfaces, energy is transferred to the surface and material damage may be triggered. Furthermore, a changing charge state of the ion alters its slowing down process in solids and has important implications when back-scattered ions are to be measured for material analysis purposes. Over the last decades extensive research was devoted to the understanding of ion charge exchange with solids. Here I review recent progress in this field with special emphasize on slow ions in high charge states. This class of ions allows a detailed analysis of charge exchange in experiments, which employ also ultra-thin solid targets and therefore give experimental access to electronic processes on the femtosecond timescale. In this review I will discuss general properties of charge exchange and present typical experimental techniques. I will also discuss current developments in the modelling and simulation of ion-surface interaction. Recent findings using freestanding 2D materials are discussed as well as results from spectroscopy of emitted secondary particles. The paper concludes with a unified picture of ion charge exchange at surfaces and presents possible applications based on the understanding of the underlying physics.     

纳秒激光电离分子团簇产生高离化离子的激光波长效应

利用脉冲分子束-激光电离-飞行时间质谱仪,在109～1012 W·cm-2激光功率密度条件下,考察了Nd：YAG激光器输出的1 064,532,266 nm波长的激光与苯、氨、硫化氢等团簇的相互作用。发现1 064 nm的激光可以电离分子束产生高离化态的C4+,N5+,S6+等离子;波长为532 nm的激光则电离产生价态较低的C3+,C2+,N3+,N2+, S4+,S3+以及S2+ 等离子;在266 nm波长条件下进行实验,没有产生任何高价离子。提出了一个“多光子电离引发-逆轫致吸收加热-电子碰撞电离”模型来解释高价离子的产生。激光场下电子在团簇内部的逆轫致加热是整个过程的关键步骤,电子被加热的速度正比于激光波长的平方。这可以解释为何长波长的激光有利于更高价态离子的产生。     

在线同位素分离装置的靶系统设计方法

产生放射性核束的在线同位素分离装置的靶系统设计是整个装置产生效率的关键环节.在ORNL的窄高斯分布的离子注入模型的基础上,研究了不同的靶的几何形状和尺寸、不同的温度条件、半衰期不同的放射性核素等对释放时间特性的影响,这对设计具有快速释放过程的靶系统,具有直接的实用价值.基于德国ZFK关于表面物理的实验测量数据,用MonteCarlo统计的方法来模拟放射性核素从靶材料表面到在线离子源的电离室的传输过程,对大量的放射性核素–传输管材料组合,和不同尺寸的传输管进行了统计计算,从这些统计计算中得到了可用于传输管工程设计的图表和经验公式.     

兰州重离子加速器分时供束的Chopper模式解析

 介绍了兰州重离子加速器分时供束系统中Chopper模式解析子系统的体系结构及硬件组成,分析了软件需求,并采用多线程技术设计了Chopper模式解析程序。首先使用NI-DAQmx函数实时读取PXI6133数据采集卡上采集的Chopper模式脉冲,然后对其作进一步分析,最后使用TCP/IP协议将相应的工作模式控制指令发送给控制器。设计的程序达到了系统要求,实现了Chopper模式自动转换的功能,并通过了现场测试。     

高电荷态离子与Si(110)晶面碰撞的沟道效应研究

不同电荷态低速离子(Ar^q+,Pb^q+)轰击Si(110)晶面,测量不同入射角情况下的次级粒子的产额. 通过比较溅射产额与入射角的关系,证实沟道效应的存在. 高电荷态离子与Si相互作用产生的沟道效应说明溅射产额主要是由动能碰撞引起的. 在小角入射条件下,高电荷态离子能够增大溅射产额. 当高电荷态离子以40°—50°入射时,存在势能越高溅射产额越大的势能效应. 关键词： 高电荷态离子 溅射 沟道效应     

带电线电场中导体球上的特定电荷分布

研究了带电导体球在带电直线电场中的电荷分布问题,并计算了两种特定情况下导体球表面的电荷密度.     

强扰动区C~(q+)离子与He原子碰撞中有效电荷研究

本文利用经典过垒电离模型(Class Over Barrier Ionization)处理100-400ke V/amu强扰动区(q/v1)的不同价态非全裸离子Cq+(q=1-4)与全裸离子H1+,He2+,Li3+与He原子碰撞过程.发现相同价态下,全裸离子的双单电离截面比R21明显低于非全裸离子,原因在于两者的电子结构明显不同.非全裸离子的外壳层电子在碰撞过程中会有一定几率过垒,这在以往的研究中并未考虑.利用模型计算结果与实验数据的比对,估计入射离子第二有效电荷,最终确定入射离子在电离过程中的第一和第二有效电荷.     

低能高电荷态氩离子与氩原子碰撞反应截面研究

使用位置灵敏技术和飞行时间方法研究了低能高电荷态氩离子与氩原子的碰撞反应,给出了实验测量得到的入射离子电荷交换截面和转移电荷截面,研究了反应截面与不同电荷态参教的关系,并与修正后的分子过垒模型计算结果进行了比较。     

Cluster-assisted generation of multiply charged ions in nanosecond laser ionization of seeded furan beam at 532 and 1064 nm

The multiply charged ions of C ^{q +} (q ≤ 4), O ^{q +} (q ≤ 6) were produced when a furan cluster beam interacted with nanosecond 1064 and 532 nm lasers at intensities of 10¹⁰–10¹² W/cm². It is shown that O⁶⁺ and C⁴⁺ ions were the dominant multiply charged species at 1064 nm, while C²⁺, C³⁺, O²⁺, O³⁺ ions were the main multiply charged species at 532 nm. By varying the electric field in the extraction region of the time of flight mass spectrometer (TOFMS), two types of ions were extracted, one of which had large kinetic energy and narrow space distribution, and the other had small kinetic energy and broad space distribution. The formation channels for He-like ions of C⁴⁺ and O⁶⁺ are discussed.     

尾流效应对快速双原子分子离子在固体中电荷态及分子轴取向的影响

研究了快速双原子分子离子在固体中穿行时,尾流效应对各离子电荷态以及库仑爆炸过程的影响.借助于线性介电响应理论和局域介电函数,离子之间的动力学相互作用势可以表示成对称的屏蔽库仑势和非对称的尾势.通过对分子离子上所有束缚电子的总能量进行变分和求解单个离子的运动方程,自洽地确定出分子离子中每个离子的电荷态.数值结果表明,由于尾流效应的影响,在初始穿行阶段,分子离子中导航离子的电荷数随穿行深度的增加而单调递增,而尾随离子的电荷数则随穿行深度的增加而振荡.但当穿行深度很大时,两个离子的电荷数都趋于具有相同速度的孤立离子的电荷数.此外,还发现分子轴的取向朝入射速度方向偏转     

The effect of negative ions on the dust acoustic wave in dusty electronegative plasma with positively charged dust grains

The effect of negative ions on the modulational instability properties of nonlinear dust acoustic (DA) waves in the electronegative dusty plasmas was investigated by considering Boltzmann-distributed electrons, negative ions, positive ions as well as positively charged dust grain under the ultraviolet irradiation. It is shown that the modulational instability properties of the DA waves were strongly affected by the temperature and proportion of negative ions. The modulational instability can occur only if the proportion of negative ions was smaller than critical value. The instability growth rate has a maximum value when the proportion of negative ions was a critical one in the unstable region. The effect of photoelectron generated by ultraviolet irradiation on the modulational instability of dust acoustic waves was also discussed by numerical method.     

低速高电荷态离子40Ar16+与云母表面作用中的电子发射研究

报道了由兰州ECR源提供的低速高电荷离子40Ar16 入射到云母表面产生的电子发射的实验测量结果.结果发现,电子发射产额Y与离子入射角ψ有近似1/tanψ的关系.基于经典过垒模型,我们对这一关系进行了理论分析.实验结果和理论结果相当符合,这就间接说明势能电子发射是低速高电荷态离子作用于表面发射电子的一个主要途径.     

Study of optical band gap and carbon cluster sizes formed in 100 MeV Si8+ and 145 MeV Ne6+ ions irradiated polypropylene polymer

A wide variety of material modifications in polymers have been studied by using ion irradiation techniques. Extensive research has focused on to Swift Heavy Ions (MeV’s energy), probably because of good controllability and the large penetration length in polymers. High energy ion irradiation tends to damage polymers significantly by electronic excitation and ionization. It may result into the creation of latent tracks and can also cause formation of radicals such as ablation, sputtering, chain scission and intermolecular cross-linking, creation of triple bonds and unsaturated bonds and loss volatile fragments. Polypropylene polymer films of thickness 50 μm were irradiated to the fluences of 1 × 10¹⁰, 3 × 10¹⁰, 1 × 10¹¹, 3 × 10¹¹, 6 × 10¹¹ and 1 × 10¹² ions/cm² with Si⁸⁺ ions of 100 MeV energy from Pelletron accelerator at Inter University Accelerator Centre (IUAC), New Delhi and Ne⁶⁺ ions of 145 MeV to the fluences of 10⁸, 10¹⁰, 10¹¹, 10¹² and 10¹³ ions/cm³ from Variable Energy Cyclotron Centre, Kolkata. Optical modifications were characterized by UV towards the red end of the spectrum with the increase of the fluence. Value of optical band gap E _g shows a decreasing trend with ion fluence irradiated with both kinds of ions. Cluster size N, the number of carbon atoms per conjugation length increases with increasing ion dose. Cluster size also increases with the increase of electronic stopping power.      

EAST中性束注入快离子损失研究

利用经典导心轨道程序ORBIT,结合平衡程序EFIT和输运程序TRANSP,计算了EAST中性束注入后快离子的损失情况.结果表明,4MW(80keV)氘离子的损失份额为29％,2MW(50keV)氘离子的损失份额为31％,损失的快离子有很强的局域性.     

兰州重离子加速器分时供束的Chopper模式解析

介绍了兰州重离子加速器分时供束系统中Chopper模式解析子系统的体系结构及硬件组成,分析了软件需求,并采用多线程技术设计了Chopper模式解析程序。首先使用NI-DAQmx函数实时读取PXI6133数据采集卡上采集的Chopper模式脉冲,然后对其作进一步分析,最后使用TCP/IP协议将相应的工作模式控制指令发送给控制器。设计的程序达到了系统要求,实现了Chopper模式自动转换的功能,并通过了现场测试。