Ar+ and Xe+ velocities near the presheath-sheath boundary in an Ar/Xe discharge

The velocities of Ar+ and Xe+ ions near the presheath-sheath boundary in an Ar/Xe discharge are studied by particle-in-cell Monte Carlo simulation. For a pure argon discharge the argon ion has almost the same velocity profile as it does in the mixture of argon and xenon. Similarly, for a xenon discharge the xenon ion has almost the same velocity profile as it does in the mixture of argon and xenon. The ion speed at the sheath-presheath boundary is the same for an ion in a pure argon or xenon discharge and for the same ion in a mixture of argon and xenon. We conclude that, in our simulation, each ion reaches its own Bohm speed at the presheath-sheath interface.     

Modelling of the Positive Column in an Argon-Hexamethyl-disiloxane dc Glow Discharge

A model is presented of the positive column of a dc glow discharge in argon with small admixtures of hexamethyldisiloxane (HMDS). The axial electric field, the ion production rates for direct-, stepwise-, pair-, and Penning ionization, the densities of metastable Ar atoms and of electrons, and the wall current of HMDS ions are calculated in dependence on HMDS admixture and discharge current density. For the calculations particle balance equations were used for a diffusion determined plasma in a mixture of two gaseous components. The reaction rates for the electron collision processes were determined applying the electron distribution function calculated for pure argon. Taking into account PENNING ionization of HMDS molecules by metastable argon atoms the decrease of electric field for increasing HMDS admixtures is according to the experimen-tally measured values. Also ion wall currents and electron densities are compared with experimen-tal values for thin film formation rate and results of probe measurements.     

Metastable Decomposition of Ar3+ Cluster Ions Into Ar2+ and Ar+

In this note we present the first account of a study of metastable (unimolecular decay) and collision-induced dissociation of Ar₃+ cluster ions using an experimental setup consisting of a molecular beam-electron impact ion source and a double focussing (reversed Nier Johnson geometry) mass spectrometer. The existence of the following metastable decay processes (accessible by our sampling time window) could be demonstrated: Ar₃⁺* → Ar₂+ and Ar₃⁺* → Ar⁺. The processes were studied as a function of electron impact energy. The present results are of importance in order to provide some guidance for the development of appropriate theoretical models for the dissociation of cluster ions.     

Radiation Efficiency and Kinetic Calculations for the Positive Column in Hg/Ar Mixtures. I. Thg Variation

Properties of the positive column of low pressure Hg/Ar discharge have been investigated from the point of view of its application in fluorescent lamps. The results obtained are based on experimental methods to determine both UV resonance radiation fluxes of the 6³ P₁ and 6¹P₁ Hg levels and to measure the electron distribution function by probes; in addition a kinetic model is applied for the theoretical interpretation of the experimental results and to give a deeper insight into the particle and energy budget. In the present first part of the paper the effects of recently determined τ_eff-values on radiation, net collision rates, power transfer and the electron energy distribution for extended parameter values are investigated especially in dependence on mercury partial pressure.     

Calculation of the optimum electron energy in an Ar+-laser plasma

Using newly available values for the relevant cross sections the electron energy at maximum laser power at 488 nm was calculated to ∼6 eV, independent of discharge current. Agreement exists between theory and a re-evaluation of experiments. To check the calculations also other Ar-laser plasma parameters were determined and compared with experiments. In the papers of Herziger and SeeligkT _e is called mean electron energy. For comparison with our results a factor 3/2 has to be considered.     

Temperature Dependence of the Rate of the Reaction N + H + Ar → NH + Ar

The rate constant for the 3 body atom recombination N + H + M with M = Ar has been measured over the temperature range 550 to 750 K in an Ar ? N₂ ? H₂ microwave flowing discharge. A temperature dependence for the rate constant is reported.     

Radiation Efficiency and Kinetic Calculations for the Positive Column in Hg/Ar Mixtures II. Impact of Tube Radius and Current Density

In a preceding part of the paper, based on experimental methods and on a corresponding kinetic model, especially the impact of the effective life times of the 6³P₁ and 6¹P₁ Hg resonance levels on the main properties of the low pressure Hg-–Ar positive column has been studied. In the presented second part these investigations, which have been performed under the aspect of their application in fluorescent lamps, will be continued. They are related to the effects of tube radius and discharge current density. New fluorescent lamps have reduced tube radii from R = 18 to 13 mm and compact lamps down to R = 5 mm. Thus it is of interest to study the electron distribution function and main macroscopic properties of such low pressure discharge plasmas, where the latter properties are obtained by adequate energy space averaging. At first, results are reported and discussed which are related to the dependence of main plasma parameters on the Hg partial pressure when reducing the discharge tube radius for constant discharge current i and argon pressure pAr. Starting from the electron distribution function the particle and energy budget will be studied in detail, especially of course the change of the ultraviolet radiation output from both Hg resonance levels 6³P₁ and 6¹P₁ and, in addition, of visible radiation. Then, to understand the effect of the discharge current density, as a representative example two cases with different values of R, i and PAr but with equal current density have been investigated and discussed. Altogether the investigations made will shed light upon the complex relations in the mentioned mixture plasma and give hints to select suitable parameter values which can be useful to improve light sources.     

KInetic Description of the Positive Column for Medium Knudsen-Numbers

We analyze the influence of collisions on a plasma column with cylindrical symmetry in the pressure regime between the collision-dominated and the free-fall case. A model is investigated which can handle arbitrary contributions from ion-neutral-collisions. One finds an analytic solution for the ion-distribution-function which depends functionally on the potential. This electrical potential is calculated numerically — with consideration of the space-charge-layer near the wall — and selfconsistently from the Poisson-equation. From the calculation of the ion-distribution-function, of density, flux and temperature of the ions as well as of the potential variation, we discuss the influence of the model parameters. The results are compared with corresponding hydrodynamic calculations.     

Single-mode operation of an Ar+ laser with an intracavity I2 absorption cell

A multi-mode argon ion laser was furnished with an intracavity¹²⁷I₂ absorption cell for the purpose of mode suppression at the wavelength of 514.5 nm. Singlemode operation was achieved with an 8 cm long cell having a¹²⁷I₂ vapour pressure of 0.27 mbar (0.2 Torr).     

Critical Current of the Ionization Waves and Anomaly of the Positive Column in an Axial Magnetic Field

Influences of an axial magnetic field on the ionization wave and the positive column in rare gas discharges are studied experimentally. The upper critical current I_c for the appearance of ionization waves in the magnetic field B is newly found. As B is gradually increased, the value of I_e slightly increases from the Pupp's value and after passing a prominent maximum, finally become very small. In addition an anomaly takes place in the axial electric field E of the positive column stable for helical instabilities. With increasing the magnetic field the value of E goes through a weak maximum before decreasing. It is concluded that this anomaly, apparently incompatible with classical diffusion theory, is closely related to the appearance of ionization waves in the positive column.     

Ar16+和Ar17+离子与Zr作用产生的X射线谱

将超导离子源提供的10-20keV/q Ar16 和Ar17 离子入射到Zr金属表面,在相互作用中产生的X射线谱表明,高电荷态Ar16 离子在金属表面中性化过程中有可能存在多电子激发,使Ar16 的K壳层电子被激发形成空穴,在退激过程中发射特征Kα-X射线.空心原子Ar的K层发射X射线强度随入射离子的动能而减弱,靶原子Zr的L壳层发射X射线强度随入射离子动能的增加而增强.Ar17 的单离子的Kα-X射线产额比Ar16 单离子的Kα-X射线产额大5个数量级.     

低能Ar3+ + Ar碰撞反应过程实验研究

测量了入射离子能量为27 keV、45 keV和66 keV时Ar3 Ar碰撞反应各子过程的分截面,通过将其归一化到Bliman,Dousson等人所测量的截面值,获得了绝对截面.结果表明,该能区电子俘获过程仍占主导地位,但转移电离过程已不能忽略.结果还表明,各子过程反应截面基本不随能量变化.与考虑自电离的MCBM(Molecular Coulombic overBarrier Model)模型比较发现,模型所给截面普遍高于实验测量值,这在一定程度上是由于归一化时带来的系统误差.在误差允许的范围内,单电子和双电子俘获截面符合的比较好,但三电子俘获截面却相差一个数量级.对于实验观测到的转移电离过程,模型却预言并没有此过程发生.     

Wavelength stabilization of an Ar+ laser with an external129I2 absorption cell

Wavelength stabilization of the green Ar⁺ laser line at 514.5 nm by¹²⁹I₂ absorption was found to be more favourable than by¹²⁷I₂ absorption because the maximum of¹²⁹I₂ absorption is closer to the center of the 514.5 nm gain curve. A simple method for stabilizing a short air cooled laser with only one servo loop is given, yielding a stability of 10⁻⁸ λ.     

AES investigations of Ar+ ion retention in Si during Ar sputtering

Argon retention in silicon has been studied by AES in the energy range between 1 and 15 keV at bombardment fluences up to ～10¹⁸ ions/cm². AES data of implanted argon in silicon near the surface region, as obtained during sputtering, can be interpreted qualitatively by a simple model of ion collection. Discrepancies between calculated and measured saturation values of collected argon ions indicate that during implantation at high fluences addition surface effects become important and that the simple model of ion collection has to account for this. Quantitative AES correlated with RBS indicates pronounced concentration gradients of argon in silicon near surface regions.     

放射性惰性气体 37Ar向地表输运的数值模拟

放射性惰性气体 37Ar的监测是全面禁止核试验条约核查体系中现场视察（OSI）的一项重要技术手段。 为在理论上考察地下核爆炸后 37Ar泄漏到地表的时间及泄漏量， 将核试验场区抽象为多孔介质， 在不考虑 37Ar在基岩中吸附、 解吸的情况下， 利用多孔介质渗流模型， 对理想场区地下核爆炸产生的 37Ar在地层中的输运进行数值模拟， 给出了 37Ar泄漏到地表时间及变化量。 计算结果可为OSI惰性气体监测技术的发展及其在地下核爆炸监测中应用的有效性评价提供参考。 Monitoring radioactive gas 37Ar is an important technique for the On Site Inspection(OSI) of the Comprehensive Nuclear Test Ban Treaty (CTBT) verification regime. In order to establish a theoretical model that can be used to calculate the appearing time and radioactivity of 37Ar which transports to the ground after a nuclear explosion， the rock media in the test area is assumed to be a homogeneous porous media， without consideration of gas absorption by and release from the rock media. The seepage model in the porous media is used to calculate 37Ar transportation. Computational results give the time 37Ar leaks to the ground and the variation of its radioactivity with time．And we can analyze and consider the computational results when we have developed OSI noble gas monitoring systems and evaluated their effectiveness.     

Preferential sputtering of TIC under keV Ar+ ion bombardment: Simultaneous sputtering-ISS measurement with He+ and Ar+ ions

The composition change of the outermost atom layer of TiC(110) under ion bombardment with 1.5–3 keV He⁺ and He⁺ + Ar⁺ ions has been measured by ion scattering spectroscopy with He⁺ ions at different sample temperatures. It has been found that the preferential sputtering of C atoms takes place for both the He⁺ and Ar⁺ ion bombardment, however the preferred sputtering is more pronounced for Ar⁺ ions than for He⁺ ions. The ion bombardment with He⁺ ions at elevated sample temperatures hardly results in any change in surface composition below ～800°C, while Ar⁺ ion bombardment results in C enrichment for elevated temperatures as reported so far.     

Modeling and Simulation of an Energy Integrated Distillation Column in a Bond Graph Approach

The bond graph methodology for modelling an integrated energy distillation column is applied in this paper. The distillation column is built by five trays for a binary mixture. However, due to its modular construction in a bond graph, the number of trays can be increased. In order to link the analysis tools of systems modeled in the bond graph to the mathematical model given to a distillation column, a junction structure of the proposed bond graph is presented. Hence, this junction structure is a way to obtain the state space representation of the modeled column in bond graphs. Likewise, it is well known that distillation columns determine a class of nonlinear systems, so throughout this paper, these systems in a bond graph approach can be analyzed. In order to learn the behavior of the distillation column in the physical domain, simulation results using 20-Sim software are shown. In addition, with the simulation of two case studies consisting of two mixtures with different relative volatilities, the versatility of the column model in a bond graph is presented. In both cases, the increase in the feed flow, the mole fraction of the light component in the feed or the distillate reflux that enriches the concentration of light in the column determine an increase in the mole fraction of light in the distillate and in the bottom reflow. Further, the control design for a distillation column in the physical domain can be extended.     

Measurement of the lifetime of the3 P 2 and4 P 5/2 states in Ar16+ and Ar15+

Promptly decaying levels in Li- and Be-like Ar could be identified in the delayed x-ray and electron spectrum in addition to the four known metastable (1s2s)¹ S ₀, (1s2s)³ S ₁, (1s2p)³ P ₂, and (1s2s2p)⁴ P _5/2 states in He- and Li-like systems. The states having lifetimes of about 10^?14s still contribute to the spectrum observed 10^?9s after the ions have passed a foil. This observation is explained by cascading processes from states of high principal quantum numbern≧14. The measured lifetime of the⁴ P _5/2 state subtracting the contribution of cascades is (0.594±0.016) ns and slightly larger than the theoretically predicted value of 0.563 ns. The³ P ₂ state is depopulated at short distances behind the foil by cascading processes. Its measured lifetime of (1.44±0.08) ns compares to a theoretical value of 1.48 ns.     

Model Calculations on the Positive Column of a Medium Pressure Neon Gas-discharge

Model calculations on the positive column of a neon gas-discharge for gas pressures between 50 and 350 torr and currents between 5 and 100 mA are presented. In these calculations a Druyvesteyn distribution for the electron energy has been used. Volume recombination and radially dependent electron and gas temperatures have been taken into account. Numerical results are compared with available experimental data. In particular, the axial field strength, electron density, electron temperature and ambipolar field strength are considered. In general, the agreement between experimental and numerical data is good.