透射型表面电离源的研制

以镍或铂等高功函数金属网为电离材料制成了间接加热式球形表面电离器，用于溅射型负离子源中，正铯离子流达到ｍＡ级，被溅射的负离子流（如Ｐ）分析后可达５０－６０μＡ。透气的电离表面增加了铯蒸汽的流量，避免了流动缓慢区的形成，并减少了污染。     

扩散型表面电离源及其在铀,钚和镎等元素质谱分析中的应用

一、引言在一般的单带表面电离源中,样品是从带表面直接蒸发和电离的,称为直接蒸发式表面电离源。这种离子源不但样品消耗快,而且电离效率也低。为了克服这些缺点,Myers和White提出把待分析样品夹馅在用高功函数、难熔金属做成的样品带和涂层薄膜之间,样品原子是以扩散方式渗透出涂层实现电离的。由于热扩散过程比直接蒸发缓慢,样品带也能在更高的温度下工作,样品原子与热表面接触的机会和时间也增加很多,既提高了电离效率,又减慢了样品消耗速度。     

用于溅射负离子源的透射表面电离器的研制

介绍了１种应用于表面电离型溅负离子源的球面形透射表面的电离器，并阐述了原理。这种电离器可使铯蒸气直接通过，避免了铯蒸气绕射造成电离表面铯原子通量低的缺点，增大了铯离子的产额也使离子源的流强较采用非透射型电离器时提高了５０－８７％。‘     

铁同位素窄电离带质谱分析

本工作采用0.4 mm宽的窄电离带,减小了由于电离带表面高温热辐射引起的本底干扰。在电离带和样品带的加热电流分别为4.0 A和1.8 A条件下,用5μg氧化铁样品可以获得10~(-13)A稳定的离子束流近1小时。用这种方法测定了电磁分离器生产的各种浓缩铁同位素产品的丰度,测定精度为0.1%。     

铯在钨(110)表面吸附行为的第一性原理研究

通过基于密度泛函理论的第一性原理计算方法,研究了铯原子在钨(110)表面上的吸附行为。计算结果表明,通过原子数之比定义的最大单层铯原子吸附率为0.4,铯原子的吸附位置随吸附率的增加而变化。铯原子吸附率为0.25时,最可能的吸附位置是长桥,而铯原子吸附率达0.4时,铯原子在钨(110)表面形成完整的单原子层,并呈现-ABA′B′-结构形式。随铯原子吸附率的增加,表面功函数先减小后增大,最终稳定在2.134 eV,其中最小值1.524 eV出现在吸附率为0.25时,该最小值低于纯铯(110)表面的功函数。偶极子模型和分态密度计算结果表明,铯原子向钨基体表面的电子转移机制和铯原子电子能量分布的变化是造成表面功函数降低的原因。     

镱同位素质谱分析

在热表面电离型离子源中采用三种样品蒸发电离方式、对镱同位素质谱分析灵敏度进行了比较。选择了合适的带工作电流和测量方法,对天然镱和电磁法制备的浓缩镱同位素丰度进行了质谱分析。     

两步激光－飞行时间质谱法测定铁和镍同位素

采用两步激光－飞行时间质谱法测定了铁和镍同位素。用５３２ｎｍ脉冲激光蒸发铁－镍合金及硫酸亚铁样品，蒸发产生的原子采用染料激光共振电离并由飞行时间质谱探测。结果表明，激光蒸发产生的原子束和共振电离激光之间具有很好的时间匹配效率，与连续加热原子化源相比，样品利用率提高了约三个量级。     

表面电离离子源束引出特性

一、引言表面电离离子源在电磁同位素分离器、质谱计、离子发动机、溅射负离子源等装置中得到了广泛的应用。使用表面源(即表面电离离子源)时,总是遇到离子束的束型问题,即表面源的引出特性问题。表面源由于产生离子的机制不同于气体放电离子源,不存在等离子体“弯月面”。离子发射面是电离器表面,它是刚体,不随引出参数和引出束流的变化而变化。因此,用表面源研究透镜效应和束空间电荷的作用是十分有利的。但到目前为止,还未见到对表面源的引出特性作系统的研究。     

软X射线作用下的InP表面微结构

同步辐射软X射线（白光）对InP表现进行了辐照。并对样品的表面电子结构作了UPS和XPS分析。结果显示，样品表面电子态变化明显，P3a峰化学位移大于In4d峰。与In非键合的P2p峰面积辐照后显增加。说明软X射线对InP表现F原子的电离损伤要大于In原子。     

丙步激光—飞行时间质谱法测定铁和镍同位素

采用两步激光－飞行时间质谱法测定了铁和镍同位素。用５３２ｎｍ脉冲激光蒸发铁－镍合及硫酸亚铁样品，蒸发产生的原子采用染料激光共振电离并由飞行时间质谱探测。     

On the velocity dependence for negative ionization of atoms sputtered from cesiated surfaces: An experimental study

The experiments here reported were performed to study the velocity dependence of the negative ions M⁻ ejected from a metal M when the surface work function is lowered by adsorption of cesium atoms.The decrease in the work function induces very similar exponential increases for all initial energies. The measured variations, reaching 3 to 5 orders of magnitude, are attributed essentially to variations of ionization probabilities. Thus the velocity dependence, predicted by theoretical studies derived from the initial work of Blandin et al. could not be established for the negative metallic ions. Besides, some other investigated ion species, H⁻, P⁻ and O⁻, experience more direct velocity dependent ionization processes. Chemical bonds may alter the ionization process. In all cases, the ionization process can still be attributed to an electron attachment on an acceptor level of the ejected particle. However, multielectronic transitions or electronic excitations during the ejection have to be considered. Such an approach has been proposed by Sroubek for positive ion emission.     

Study of low work function materials for hot cavity resonance ionization laser ion sources

The selectivity of a hot cavity resonance ionization laser ion source (RILIS) is most often limited by contributions from competing surface ionization of the hot walls of the ionization cavity. In this article we present investigations on the properties of designated high temperature, low work function materials regarding their performance and suitability as cavity material for RILIS. Tungsten test cavities, impregnated with a mixture of barium oxide and strontium oxide (BaOSrO on W), or alternatively gadolinium hexaboride (GdB₆) were studied in comparison to a standard tungsten RILIS cavity as being routinely used for hot cavity laser ionization at ISOLDE. Measurement campaigns took place at the off-line mass separators at ISOLDE/CERN, Geneva and RISIKO/University of Mainz.     

Effect of Fe ion implantation on tribological properties and Raman spectra characteristics of diamond-like carbon film

1 Introduction It is well known that DLC (diamond-like carbon)prepared by physical vapor deposition, plasma en-hanced chemical vapor deposition (PECVD) and otherplasma processing is an amorphous carbon materialcontaining sp2 and sp3 bonded carbon atoms. DLCfilm possesses some interesting properties, such ashigh hardness and Young's modulus, chemical inert-ness and low friction coefficient. The property andstructure of DLC film can be modified by addingsome metals. Ion implantation…     

Charge state of low energy reflected particles

Low energetic noble gas particles, scattered from a metal surface, have only a small probability to leave this surface in the charged state. Even particles scattered from target atoms in the outermost surface layer are nearly all neutralised. Consequently analysis of the charged fraction of the scattered beam guarantees that information is obtained of only this layer. To quantify these low energy ion scattering (LEIS) measurements data on the ion fractions must be known, especially because these fractions have such small values. Besides this practical aspect there is the fundamental question: how does it work, this neutralization mechanism, does the transition rate for electron capture of the scattered particle depend upon its distance from the surface, or are it distant binary collisions with individual metal atoms along its trajectory which give rise to interatomic Auger transitions.Already for many years Hagstrum's theory has been applied to correct for the neutralization effect. This theory is developed to study the ejection of Auger electrons as a result of the interaction of low energetic noble gas ions with a metal surface. Due to the low ion energies used in those experiments, namely the tens eV-region, Hagstrum assumed a structureless metal surface. This means that the normal velocity of the scattered particle, v₁, takes part in determining the ion fraction and not v, the velocity of the scattered particle in its trajectory. It is a question, however, whether this theory may be applied for keV-ions. The distance between scattered particle and metal surface is for these energies namely much smaller than for tens eV's and the surface can no longer be regarded as a plane; this may result in dominating interatomic Auger transitions. But then the trajectory of the scattered particle with its velocity v plays a part in determining the occurrence of neutralization.Another mechanism that may determine the charge state of the scattered particle occurs in the violent collision; neutralization as well as (re)ionization of this particle may take place and influence its charge state. These models are treated in this review and discussed with the help of recent measurements and results of computer simulations of reflected particles.     

The influence of projectile charge state on ionization probabilities of sputtered atoms

The ionization probability of atoms sputtered from a clean polycrystalline metal surface was measured for different charge states of the projectile used to bombard the sample. More specifically, a polycrystalline indium surface was irradiated with Ar⁺ and Ar⁰ beams of energies between 5 and 15 keV, and In⁺ secondary ions and neutral In atoms emitted from the surface were detected under identical experimental conditions regarding the sampled emission angle and energy. The resulting energy integrated ionization probability of sputtered In atoms is consistently found to be smaller for neutral projectiles, the difference decreasing with decreasing impact energy. The observed trends agree with those measured for kinetic electron emission, indicating that secondary ion formation is at least partly governed by kinetic substrate excitation.     

On the understanding of positive and negative ionization processes during ToF-SIMS depth profiling by co-sputtering with cesium and xenon

In this paper, ionization processes of secondary ions during ToF-SIMS dual beam depth profiling were studied by co-sputtering with 500 eV cesium and xenon ions and analyzing with 25 keV Ga⁺ ions. The Cs/Xe technique consists in diluting the cesium sputtering/etching beam with xenon ions to control the cesium surface concentration during ToF-SIMS dual beam depth profiling. Several depth profiles of a H-terminated silicon wafer were performed with varying Cs beam concentration and the steady state Si, Xe and Cs surface concentrations were measured in situ by Auger electron spectroscopy. It was found that the implanted Cs surface concentration increases with the Cs fraction in the beam from 0% for the pure Xe beam to a maximum Cs surface concentration for the pure Cs beam. Secondly, the variation of the silicon work function, due to the Cs implantation, was measured in situ and during depth profiling as the shift of the secondary ion kinetic energy distributions. Finally, the positive and negative elemental ion yields generated by the Ga analysis beam were recorded and modeled with respect to varying Cs/Xe mixture. We found that the Si⁻ and the Cs⁻ yields increase exponentially with the decrease of the silicon’s work function while that of Cs⁺ and Si⁺ decrease exponentially, as expected by the electron tunneling model.     

BRISOL钾同位素放射性核束的产生

北京放射性核束装置在线同位素分离器（BRISOL）采用一台100 MeV回旋加速器提供的最大200 μA的质子束打靶在线产生放射性核束,其最高质量分辨率好于20 000。2015年,BRISOL装置建成并使用05 μA质子束轰击氧化钙靶产生了37K+、38K+放射性核束,其中38K+的产额为1×106 pps。为了提高氧化钙靶产生钾放射性核束的产额以满足物理用户需求,BRISOL于近期开展了氧化钙靶的在线实验。实验中使用氧化钙靶产生了36～38K+、43K+、45～47K+等多种放射性核束,同时将38K+的最大产额提高到了112×1010 pps。本文详细介绍氧化钙靶的研制及在线实验结果。     

Structural Material Anomaly Detection System Using Water Chemistry Data, (II)

A calculation model was developed to predict the dose rate, caused by ⁵⁸CO which is formed by the activation of ⁵⁸Ni, around the recirculation pipes m boiling water reactors (BWRs). The model is characterized by considering direct deposition of Ni ion on the nuclear fuel cladding surface and the geometrical contact probability for the ferrite formation reaction between deposited Ni(Co) and Fe₂O₃ on fuel cladding surface.

This model showed the important role of the amount of Fe crud on the surface to reduce ⁵⁸CO ion concentration in the reactor water. And the necessary Fe concentration in the feedwater for reducing the dose rate in the primary system was estimated as a function of the operating time. This model also enables the quantitative predictions of the effect of prefilming treatment of the feedwater heater tubes or another methods to reduce dose rate in an Fe crud suppressed BWR.     

Ion bombardment induced surface electrical degradation monitoring by means of luminescence in aluminas

Oxide ceramics for use as electrical insulators in future fusion devices, will be exposed to ionization and displacement damage (neutrons, gammas, ion bombardment). Enhanced oxygen loss due to ion bombardment increases surface electrical conductivity, and at the same time the surface emits light due to ion beam induced luminescence (IBIL). Results for 3 types of α-alumina and sapphire measuring electrical surface conductivity and IBIL as a function of dose at different temperatures between 20 and 200 °C, show a clear correlation between luminescence and surface electrical degradation. This indicates the potential to remotely monitor insulating material degradation not only in ITER and beyond, but also in the more immediate in-reactor experiments required for materials testing. Partial reduction of degradation by heating in air suggests the possibility for in situ recovery of the insulating properties.