摘要:

It is shown experimentally that the electron charge emitted from triglycine sulfate pulse ferroelectric cathodes can be as large as 129 &mgr;C/cm2. This charge considerably exceeds the measured value of spontaneous polarization,Ps=2.8 &mgr;C/cm2. A bipolar voltage is found to facilitate the appearance of the electron emission. It is proposed that the source of the emission current is the plasma of uncompleted surface discharges. This plasma is initiated at the metal‐vacuum‐dielectric triple points both by the field electron emission and the electron emission stimulated by polarization switching. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360758

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

This work studies the dynamics of melting in current‐carrying conductors. Formulae are derived which describe the dependence of temperature at the front of phase transition upon the distance from the axis of the conductor. The thermodynamic stability of a phase transition front is investigated. It is shown that due to strong variations of conductivity during melting the rate of change of conductivity is of the same order as an active resistance of a conductor. Clearly the magnitude of this effect depends upon the ratio of electric conductivities in liquid and solid phases. The effect is stronger when this ratio is lower. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360141

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The Phillips Laboratory working fluid experiment is a research effort to study the compression of a hot hydrogen gas using an electromagnetically imploded solid liner. In our experiments, the solid liner is driven by a 5 MJ discharge which Joule heats the aluminum, melting and eventually vaporizing it. This numerical study explores the vaporization and flux penetration of a solid aluminum liner during its implosion. In particular, it considers the effect that flux which has penetrated the liner has on the hot hydrogen working fluid. A study of the dynamics of the solid liner was performed with one‐dimensional radiation magnetohydrodynamic simulations, which included a careful treatment of the electrical resistivity near the phase transitions. An analytic snowplow model is developed in order to estimate the minimum working fluid density required to ignore flux penetration through the liner.

ISSN:0021-8979    

DOI:10.1063/1.360142

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A plasma chemistry model is presented that explains the observed CO2dissociation levels in a closed‐cycle fast‐axial‐flow CO2laser. The model includes reactions between the neutral species CO2, CO, O, O2, O3, H2O, and OH, and the negative ions O−, O−2, CO−3, and CO−4. Dissociation rates are computed by solving the electron Boltzmann equation for experimental values of the reduced fieldE/N. It is found that gas replenishment and the neutral recombination reaction between CO and the OH radical are the most effective mechanisms to suppress the CO concentration in the gas circuit. The influence of CO2dissociation on the laser output power level is discussed. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360143

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A particle‐in‐cell (PIC) simulation of an axisymmetric electron‐cyclotron‐resonance (ECR) etching tool is developed in which up to 2×106particles per species are loaded in a two‐dimensional spatial computational mesh (r,z), along with three velocity components (vr,v&thgr;,vz). An ECR heating scheme based on single‐particle trajectories in the resonance zone generates the simulated plasma. Electron‐ and ion‐neutral elastic and inelastic collisions are treated by a null Monte Carlo collision method. The code generates the electron and ion‐velocity distributions, plasma potentials, and densities in a CF+3/CF4etching plasma. In addition, a novel scaling technique which bridges the gap between the ion and electron‐time scales and accelerates the rate of convergence of the code is introduced for a PIC code. The predictions of the code show that microwaves are completely absorbed before reaching the exact location of resonance. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360144

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The most important forces that influence the motion of particles in a glow discharge plasma are the electrostatic force, the ion drag force, the neutral drag force, thermophoresis, and gravity. In this article we present a transport model that predicts the distribution of particles in plasma reactors in terms of the fundamental forces that act on the particles. We compare the model predictions to experimental measurements of particle distributions in a rf parallel plate plasma reactor. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360145

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Based on the analysis of the micro‐processes due to the interaction of synchrotron radiation with materials, we have developed a theoretical method to calculate the heat energy deposited when synchrotron radiation passes through insert devices (filters, mirrors or monochromators). The micro‐processes are photoionization, Compton scattering, Rayleigh scattering, electron elastic and inelastic collisions, electron Bremsstrahlung scattering and the Auger process. The energy of x rays is converted into the electrons’ kinetic energy and atomic excitation energy by photoionization and Compton scattering. High‐energy photoelectrons slow down mainly through inelastic collisions with the atoms in materials. The energy deposition in a material is simulated according to the x‐ray atom interaction cross sections and photoelectron‐atom collision cross sections. The results of a calculation for x rays traversing Si and Be plates of 1.0 cm in thickness are presented and discussed as one typical example concerning important materials in optical devices. The dependence of the energy deposition on the angle of incidence of the x rays is also discussed. Both the utility and validity of the present simulation method are discussed. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360146

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A boron doped epilayer was used to investigate the interaction between end of range dislocation loops (formed from Ge+implantation) and excess point defects generated from a low dose 1014/cm2B+implant into silicon. The boron doping spike was grown in by chemical vapor deposition at a depth of 8000 A˚ below the surface. The intrinsic diffusivity of the boron in the doped epilayer was determined by simply annealing the as‐grown layer. The end of range (type II) dislocation loops were created using two overlapping room‐temperature Ge+implants of 75 and 190 keV each at a dose of 1×1015/cm2. Upon annealing the amorphous layer regrew and a layer of type II dislocation loops formed ∼2300 A˚ deep at a density of ∼8×1010/cm2. The enhancement in the buried boron layer diffusivity due to the type II loop forming Ge+implant was observed to increase approximately between 2.5 and 5 min from 1500× to a value 2500× above the intrinsic diffusivity before dropping back to intrinsic levels after 30 min at 800 °C. A low‐energy (8 keV) 1×1014/cm2B+(Rp=320A˚) implant into material without loops resulted in an average enhancement of 1540× in boron epilayer diffusivity after 2.5 min at 800 °C. The enhancement dropped down to intrinsic diffusivity levels after 5 min at 800 °C. When a layer of loops was introduced and annealed prior to and deeper than a subsequent low‐energy B+implant, annealing of the B+implant produced no measurable enhancement in the buried B layer diffusivity. Taken together this imples that the interaction kinetics between the dislocation loop layer and the damage induced interstitials are primarily diffusion limited and the loops are absorbing a significant fraction of the interstitials produced by the low‐energy B+implant. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360147

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Antimony/aluminium films in bilayer and multilayer geometries were irradiated at liquid‐nitrogen temperature with 50–900 keV ion beams ranging in mass from20Ne to208Pb. Depth profiling of the element concentrations was carried out via Rutherford backscattering spectroscopy. The formation of intermetallic phases and phase segregation was analyzed by means of x‐ray diffraction, cross‐section transmission electron microscopy, and scanning electron microscopy. From the low‐dose irradiation data, the mixing rateskwere obtained and found to depend linearly on the energy densityFDdeposited at the interface. The mixing efficiency of Sb/Al bilayers,k/FD=296(30) A˚5/eV, supports the local thermal spike model. After high‐fluence irradiations of Sb/Al bilayers with 550 keV Xe++ions, a reacted layer of crystalline SbAl (B3phase) at the interface was observed. Sb/Al multilayers irradiated with 900 keV Xe++ions were found to become amorphous. Phase formation was studied as a function of the ion fluence, irradiation energy, and ion mass, and was found to start at that fluence, where cracking and shrinking of the Sb top layer and an increase of the sputtering yield were also observed. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360148

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The sensitivity to x‐ray beam energy of structure measurements using x‐ray standing waves (XSW) generated under conditions of total external reflection has been determined. To this end, the optical properties of the system were examined in a theoretical analysis to identify possible energy‐dependent components such as surface roughness. The analysis shows that, provided surface roughness is small (Debye–Waller factor less than 10 A˚) and the energy range covered in the XSW measurements lies within several keV, its contribution can be accounted for satisfactorily by a simple Debye–Waller factor. In addition, a series of XSW measurements were made on Langmuir–Blodgett films of manganese arachidate (C20:0) on a gold mirror surface at three incident x‐ray beam energies in the 7–11.2 keV range. The XSW data were analyzed to account for the Debye–Waller factor. No obvious dependence on incident x‐ray energy was found. These results demonstrate that the contribution of surface roughness to the x‐ray fluorescence yield profile is minimal under these conditions. Thus, mirrors of the type and quality used in these experiments are useful in XSW measurements where multiple element types are incorporated as structural labels in organic thin films and at surfaces. We also demonstrate that the resolving power of the XSW method is sufficient to distinguish and to locate two separate probe atom layers in a single Langmuir–Blodgett film. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360759

出版商:AIP    

年代:1995

数据来源: AIP