Charge Exchange between Hydrogen Atoms and Fully Stripped Heavy Ions

Charge exchange between multicharged ions and background atomic and molecular gases represents one of the limitations to the attainment of high charge states in heavy ion sources, particularly containment sources. This work is an attempt to study systematically a particularly simple but in many respects representative class of such reactions, namely, charge transfer between atomic hydrogen and fully stripped heavy ions. Approximate cross sections for these processes in the low keV range of collision energies were obtained using a multistate Landau-Zener method. The energy and Z dependences of the cross sections are discussed.     

Production of Sm Negative Ions for AMS Measurement

^151Sm with its half-life of 90 years is a long-lived radionuclide. It is very interesting for nuclearphysics and environment science to detect trace amount of ^151Sm. But the content of Sm in samples is very low especially in biological samples （ppm-ppb）,     

氦离子辐照下金属钯薄膜的微观行为研究

采用电子束蒸发镀膜技术,在Si(100)面基底上沉积金属钯薄膜,并采用台阶仪和透射电子显微镜(TEM)对薄膜的厚度和结构进行表征.选取不同能量、不同剂量的氦离子束对钯薄膜进行注入实验,注入后,用X射线衍射分析(XRD)分析薄膜的微观行为.实验结果显示,在固定注入能量时,随着注入剂量的增加,钯薄膜的晶格发生膨胀,膨胀与注入造成的离位钯原子以及氦-空位复合物在晶格中的存在有关.原子力显微镜(AFM)和扫描电子显微镜(SEM)的测试结果表明,由于溅射作用,薄膜表面变得略为平坦.     

Formation of Gas Pores in Nickel Alloys and Structural Steel under Irradiation by Helium Ions

Transmission electron microscopy is used to study the development of helium porosity in binary alloys of nickel with elements possessing a different dimensional atomic mismatch with nickel – from negative (beryllium and silicon) to positive (molybdenum, tungsten, aluminum, titanium, tantalum, tin, and zirconium), in structural steels ChS-68, ÉP-150, and the nickel alloy KhNM. The gas pores were produced by irradiation with 40 keV He⁺ up to fluence 5·10²⁰ m^–2 at 650 and 20°C followed by annealing at 650°C for 1 h. It is shown that under high-temperature annealing beryllium and silicon, relative to nickel, give rise to the formation of larger bubbles, while elements with a larger positive size mismatch with nickel atoms substantially decrease the size and increase the density of the bubbles. On the whole, as atomic radius and the concentration of the alloying element increases in alloys, the gas swelling of the irradiated layer decreases. Under post-irradiation annealing, bubbles with the largest diameter and the lowest density develop in nickel. Any alloying used decreases the size and increases the density of bubbles. The data obtained are discussed from the standpoint of the formation of various vacancy complexes of helium and their thermal stability.     

Collective Acceleration of Protons and Helium Ions in the Garching ERA

Collective acceleration of hydrogen and helium ions by relativistic electron rings has been achieved in the Garching ERA. It features fast electron ring compression and smooth magnetic expansion acceleration. Acceleration of the confined ions was demonstrated by the increase of inertia with the load of the rings and by nuclear track recording.     

Microscopic Damage of Tungsten and Molybdenum Exposed to Low-Energy Helium Ions

Polycrystalline tungsten(W)and molybdenum(Mo)materials both non-annealed and annealed at temperatures of 800-1750~C have been irradiated with low-energy(220 eV),high-flux(~10~(21)ions/m~2.s)He~+at an irradiation temperature of 600℃and at a dose of1.0×10~(25)ions/m~2.This non-destructive conductive atomic force microscopy technique provides direct observation and comparison of surface swellings with growth of nanoscale defects in the irradiated materials.A coral-like surface structure and nanostructured defects were formed in W when irradiated at a He+dose of 1.0×10~(25)ions/m~2.Increasing the annealing temperature resulted in an increase in the size of nanostructured defects and serious surface damage of W.Compared to W,Mo suffered much less surface damage after being irradiated at various He~+doses.     

Charge Exchange Effect on Space-Charge-Limited Current Densities in Ion Diode

The article theoretically studied the charge-exchange effects on space charge limited electron and ion current densities of non-relativistic one-dimensional slab ion diode,and compared with those of without charge exchange.     

Production of Ultra-High Charge States in Heavy-Ion Collisions

Charge-state fractions have been determined for iodine, selenium and bromine ions traversing oxygen, argon, krypton, xenon, carbon-foil and gold-foil targets. Particular attention has been paid to high charge states, some containing as little as 10-6% of the primary beam intensity. The measurements indicate that a TU tandem accelerator is capable of delivering useful beams of heavy elements up to bromine (including 82Se and 48Ca) with energies suitable for the research of super-heavy elements.     

An Obliquely Propagating Electromagnetic Lower-Hybrid-Drift Instability in Plasmas with Negative Ions

In this study, by employing a local fluid theory for warm plasma containing negative ions, an obliquely propagating electromagnetic instability in the lower hybrid frequency range driven by cross-field currents or relative drifts between electrons and ions was investigated. It is found that the growth rate of the lower-hybrid-drift instability （LHDI） can be controlled by appropriate selection of the propagation direction, the wave number and the relative population of the negative ions.     

MeV离子轰击碳样品引起的碳氢团簇产额

利用北京大学2×1.7MV静电串列加速器产生的1.5MeV Au2+和Si+束流轰击碳纳米管样品,用二次离子飞行时间质谱方法分析了二次离子成分,通过质量已知的样品的定标,确认了轰击产生的二次离子质量。分析束流轰击后的二次离子产额,发现在此能量下二次离子产额与离子在物质中射程的横向歧离表现出正相关。     

X-rays Production by 15-55 MeV Carbon Ions Striking Metal Surfaces

A-100区奇奇核存在着丰富的核结构信息，例如形状共存、三轴形变、带终结以及磁转动带与手征二重带等。在前人的实验结果中，^112In的高自旋态信息很少，仅观测到10ˉh。本次实验的目的是为进一步研究^112In的高自旋态结构，并且寻找其可能存在的磁转动带与手征二重带。     

Determination of Average Ion Temperature of the TVD Tokamak by a Simple Charge Exchange Analyzer Detector

In this paper the average ion temperature of the TVD tokamak plasma is determined by a low cost charge exchange analyzer. When the neutral beam energy was equal to 3 keV, the stripping efficiency was 0.065. Estimated average ion temperatures for cold and hot regions of the plasma were 100 and 650 eV, respectively. Unlike the cold region of the plasma in which ion temperature was not related to the time, ion temperature in the hot region was maximum when the plasma current reached its maximum value.     

Flow Characteristics and Charge Exchange Effects in a Two-Dimensional Model of Electrothermal Plasma Discharges

Electrothermal (ET) plasma discharges are capillary discharges that ablate liner materials and form partially ionized plasma. ET plasma discharges are generated by driving current pulses through a capillary source with peak currents on the order of tens of kA and pulse lengths on the order of \(100\,\upmu \hbox {s}\). These plasma discharges can be used to propel pellets into magnetic confinement fusion devices for deep fueling of the fusion reaction, ELM mitigation, and thermal quench of the fusion plasma. ET plasma discharges have been studied using 0D, 1D, and semi-2D fluid models. In this work, a fully 2D model of ET plasma discharges is presented. The newly developed model and code resolve inter-species interaction forces due to elastic collisions. These forces affect the plasma flow field in the source and impede the development of plasma pressure at the exit of the source. In this work, these affects are observed for discharge current pulses peaking at 10 and 20 kA. The sensitivity of the model to the inclusion of charge exchange effects is observed. The inclusion of charge exchange has little effect on the integrated, global results of the simulation. The difference in total ablated mass for the simulations caused by the inclusion of charge exchange reactions is <1 %. Differences in local plasma parameters are observed during discharge initialization, but after initialization, these differences diminish. The physical reasoning for this is discussed and recommendations are made for future modeling efforts.     

锂冷空间堆辐照产氦行为研究

锂(Li)是一种重要的空间核反应堆传热工质,采用Li冷却的大功率空间堆是未来空间核电推进任务的理想能源之一。Li在受中子辐照时会产生氦(He)。在Li冷空间堆中,Li产生的He会对一回路的热工水力造成不利影响,需要设置气体分离器对其进行收集。因此,对Li辐照产He的计算和研究是Li冷空间堆设计的重要环节。为详细研究Li冷空间堆的产He行为,构建了兆瓦级Li冷空间堆LISA,采用三维蒙特卡罗程序MCNP,对反应堆中Li产He行为进行了计算,比较了不同反应以及不同区域的产He量,研究了Li-7丰度以及中子能谱对产He的影响,并基于研究结果提出了Li冷空间堆的优化思路。本研究的方法和结论可为Li冷空间堆的设计研究提供有益参考。     

Collisions of Highly Stripped Ions at MeV Energies in Gas Targets: Charge Transfer and Ionization

We have measured cross sections for charge transfer and ionization in H2 and rare-gas targets by fast, highly ionized Carbon, iron, niobium, and lead ions in charge states +3 to +59, with energies in the range 0.1-4.8 MeV/amu. Experimental results are compared with classical-trajectory calculations; agreement is generally good. For a given target, the cross sections for net ionization reduce to a common curve when plotted as cross section divided by charge state versus energy per nucleon divided by charge state.     

3He的产生对钛氚化物性能的影响

文章基于第一原理对T衰变成3He后钛氚化物体系的电子结构及弹性模量进行计算。计算结果表明:TiT2中衰变产生的3He将占据体积较小的四面体间隙,并非占据体积较大的八面体间隙;3He的产生加强了最近邻的T原子与Ti原子的成键作用,Ti—T总的平均成键作用增强,这是氚化物时效后平衡压降低的原因;3He产生后,体系Ti—T键的大量损耗是体系体模量急剧下降的原因。     

氦中痕量杂质气体气相色谱检测分析方法研究

为实现聚变堆氘氚燃料工艺气中痕量杂质气体组分的快速检测分析,需建立特殊的高精度在线气相色谱检测分析方法。以高纯氦作为载气,在不同的色谱柱温度和载气流速控制下,通过分子筛毛细管柱和PLOT-Q柱进行分离,采用放电氦离子化检测器（DID）进行检测,对氦中含量为1、10以及100 ppm的杂质标准气体进行检测分析。结果表明：在柱温为40 ℃、流速为15～20 mL/min实验条件下,分子筛柱在160 s内能够实现H₂、O₂、N₂、CH₄和CO全部分离,且柱效较高,响应值的重复性较好,H₂和O₂之间的分离度高于1.5,实现了完全分离;在柱温为40 ℃、流速为20 mL/min时,PLOT-Q柱分离CO₂组分效果最佳。