摘要:

We consider the spectroscopy and atomic physics for some highly ionized Cr, Fe, and Ni ions produced in tokamak plasmas. Specifically, we consider both allowed and forbidden transitions between levels of the 2s22pk, 2s2pk+1, and 2pk+2configurations. Forbidden and intersystem wavelengths for Cr and Ni ions are extrapolated and interpolated using the known wavelengths for Fe lines identified in solar‐flare plasmas. We present tables of transition probabilities for theBI,CI,NI,OI, andFIisoelectronic sequences, and give collision strengths and transition probabilities for Cr, Fe, and Ni ions of theBeIsequence. Proton excitation rate coefficients for fine‐structure transitions in theBeIthroughFIsequences are tabulated, as well as populations of all levels of the 2s22pk, 2s2pk+1, and 2pk+2configurations for Cr, Fe, and Ni for theBeIsequences, and for Cr and Ni for theBI‐FIsequences. We discuss similarities of tokamak and solar spectra, and show how the atomic data we have presented may be used to determine ion abundances and electron densities in low‐density plasmas.

ISSN:0021-8979    

DOI:10.1063/1.327399

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Model equations for the implosion of multiple‐wire arrays mounted across the electrodes of a transmission line generator are used to obtain an expression for the energy‐coupling efficiency. For a useful class of imploding loads, the efficiency is shown to depend on a single dimensionless parameter. Furthermore, the efficiency curve has a maximum, and this permits an explicit optimization of the wire load parameters in terms of the machine parameters.

ISSN:0021-8979    

DOI:10.1063/1.327410

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Energy absorbed by spherical‐shell targets irradiated using the KMSF ellipsoidal‐mirror illumination system at powers on target of up to 1.0 TW has been measured using a thermopile differential calorimeter. Data are presented for 1.06 and 0.532‐&mgr;m laser light, for glass and low‐atomic‐number PVA targets, and for laser configurations with and without a plasma spatial filter.

ISSN:0021-8979    

DOI:10.1063/1.327411

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The preionization level and other initial conditions necessary for the formation of spatially homogeneous pulsed avalanche discharges at high gas pressures are examined. Assuming properly shaped electrodes with no strong edge effects, the minimum preionization level required for homogeneous discharge initiation is found to depend on the voltage rise time across the electrodes as well as on the total pressure and various electrochemical properties of the gas mixture which govern the net rate of change of the first Townsend coefficient with respect to the local electric field strength. Our predictive results are found to be consistent with experimental observations.

ISSN:0021-8979    

DOI:10.1063/1.327412

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Experimental and theoretical studies were conducted on plasma in a supersonic channel containing a transverse plate discharge and localized pin‐discharge ionizers. The goal was to determine the mechanism by which the plasma was created and distributed in such a discharge channel, where a nitrogen flow and both discharges operated continuously. Spatially resolved measurements of neutral density (N?1018cm−3), flow velocity (u?540 m/s), voltage distribution between the discharge plates (voltage drop ?2 kV), and plasma density distributions have allowed for the determination of such plasma properties as the ratio of electric field to total number density (E/N?10−16V cm2), the ambipolar diffusion coefficient (Da?40 cm2/s atN?1018cm−3), and the average electron energy (&egr;?0.1 eV). The experimentally determined plasma density distributions are shown to be consistent with the predictions of a continuum quasineutral convection‐diffusion model with pin‐discharge source terms. The theory models all the major features of the plasma flow in the discharge channel, and can be used for future design studies of potential laser devices.

ISSN:0021-8979    

DOI:10.1063/1.327413

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

We present results obtained when a TEA‐CO2laser pulse is radially incident on a dense hydrogenZ‐pinch plasma. Perturbations of the plasma column are visible on high‐speed streak photographs. Spectral measurements indicate that stimulated Brillouin scattering in the underdense plasma regions is the dominant mechanism for the observed backscattering of laser radiation by the plasma column. The time behavior of the backscattered signal can be very complex, both prompt and delayed backscatter having been observed under ostensibly identical experimental conditions. The backscattered power is typically 1–2% of the incident laser power.

ISSN:0021-8979    

DOI:10.1063/1.327415

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

A new mathematical model for the electrical conditions in wire‐duct electrostatic precipitators is described. The model is based on the solution of Maxwell’s equations for the electric field components and offers several advantages over numerical solutions of Poisson’s equation. The model is used to calculate the effects of back corona on (1) the voltage‐current characteristic, (2) the current‐density distribution at the collector plate, and (3) particle collection for five simple mechanisms describing the generation of back corona. Each mechanism is capable of simulating theV‐Icurves characteristic of precipitators operating in back corona, but two in particular are identified as potential back corona mechanisms on the basis of generating hysteresis in theV‐Icurves or characteristic current density variations. These mechanisms are consistent with limited experimental data. This method of calculation is useful and can be extended to more complex mechanisms for back corona generation.

ISSN:0021-8979    

DOI:10.1063/1.327416

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The paper presents a study of the cyclotron waves in a plasma column enclosed in a conducting cylinder and placed in an axial static magnetic field. The cutoff frequencies of the waves are investigated with special reference to the role of the plasma radiusain the wave propagation. The cyclotron modes discussed cover all the possible types, namely, circularly symmetricCommodes and asymmetricCnmmodes withn?1, eachCnmmode being split into two, designated asC−nmandC+nmmodes, corresponding to two different polarizations of the field components. The upper and lower limits of the cutoff frequencies of the various modes asatends to zero and infinity, respectively, are derived. It is found that cyclotron modes can broadly be divided into the following two categories: (1)C+n1modes, the limiting cutoff frequencies of which are the electron cyclotron frequency &ohgr;ceand lower hybrid frequency &ohgr;lh, and (2) modes other thanC+n1modes, the limiting frequencies being the upper hydrid frequency &ohgr;uhand a frequency &ohgr;0which is a function of electron and ion plasma frequencies, &ohgr;peand &ohgr;pi, as well as electron and ion cyclotron frequencies, &ohgr;ceand &ohgr;ci. The modes belonging to the first category represent, in all cases, forward waves while those of the second category may represent backward or forward waves, depending essentially onaif &ohgr;peand &ohgr;ceare kept constant. The critical radii at which the change takes place for the lowest‐order modes are derived. The effect of plasma ions on the propagation of theC+n1modes is found to be considerable ifais sufficiently large. For other modes the effect can be considerable if bothaand &ohgr;cehave sufficiently high values.

ISSN:0021-8979    

DOI:10.1063/1.327417

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

The effects of the recoil implantation of oxygen on the electrical properties of Si heavily implanted with As through SiO2films have been investigated as a function of annealing temperature, in correlation with the crystal orientation. The concentration profiles of the electrically active As in Si have been compared with those of total As and recoil implanted oxygen measured by secondary‐ion mass spectrometry. It is shown that at temperatures between 650 and 850 °C, both the restriction in the electrical activation and the reduction of mobility are observed in the region where the oxygen concentration exceeds ∼1020O/cm3in (111) ‐oriented Si, while the recoil implantation of oxygen has much less influence on the electrical properties of Si in (100) ‐oriented Si. At 1000 °C the only effect of the recoil implantation is the reduction of mobility in the surface region in (111) ‐oriented Si. The analysis of the defect structures by transmission electron microscopy indicates that the defects in (111) ‐oriented Si after annealing are much denser than those in (100) ‐oriented Si. The isochronal annealing are much denser than those in (100) ‐oriented Si. The isochronal annealing behavior of carrier concentration is correlated with that of defects measured by ESR method.

ISSN:0021-8979    

DOI:10.1063/1.327418

出版商:AIP    

年代:1980

数据来源: AIP

摘要:

Surface‐ and inner‐microdefects examined after a two‐step annealing process are compared and related to the intrinsic gettering phenomenon. After the defects are characterized by means of transmission electron microscopy, the defect types (dislocations, precipitates, and stacking faults) and defect structures as well as nature are correlated with the annealing temperature. It is found from the observations that a surface‐microdefect is a stacking fault extrinsic in nature possibly caused by a process‐induced ’’heavy metal contamination’’ such as copper and that the type of Si‐O complex precipitates generated strongly depends on annealing temperatures: <1050°C⋅⋅⋅ platelike cristobalite, 1100°C<⋅⋅⋅ regular octahedral amorphous SiO2. In addition, the mechanism for the formation of these defects is discussed based on electron microscope observations.

ISSN:0021-8979    

DOI:10.1063/1.327419

出版商:AIP    

年代:1980

数据来源: AIP