Polarization of coherent synchrotron radiation from an electron beam rotating in a plasma

After eliminating reflections from the walls of the plasma container, we observed polarization of the coherent synchrotron radiation from a relativistic electron beam rotating in a plasma. Several features of the polarization agree well with calculations based on the single particle synchrotron radiation theory. A particular polarization ratio (Fig. 3) does not, however. We deduce from this direct diffraction of the radiation by the beam electrons. This is strong evidence for beam-particle bunches of size ～cm. Also, there must be some absorption of the extraordinary wave to account for the observations. We suggest a way to apply these results to measure the pitch angle of the beam.     

Constitutive relations on creep for SnAgCuRE lead-free solder joints

Taking the most promising substitute of the Sn-3.8Ag-0.7Cu solder as the research base, investigations were made to explore the effect of rare earths (REs) on the creep performance of the Sn-3.8Ag-0.7Cu solder joints. The SnAgCu-0.1RE solder with the longest creep-rupture life was selected for subsequent research. Creep strain tests were conducted on Sn-3.8Ag-0.7Cu and SnAgCu-0.1RE solder joints in the intermediate temperature range from 298 K to 398 K, corresponding to the homologous temperatures η=0.606, 0.687, 0.748, and 0.809 and η = 0.602, 0.683, 0.743, and 0.804, respectively, to acquire the relevant creep parameters, such as stress exponent and activation energy, which characterize the creep mechanisms. The final creep constitutive equations for Sn-3.8Ag-0.7Cu and SnAgCu-0.1RE solder joints were established, demonstrating the dependence of steady-state creep rate on stress and temperature. By correcting the apparent creep-activation energy of Sn-3.8Ag-0.7Cu and SnAgCu-0.1RE solder joints from the experiments, the true creep-activation energy is obtained. Results indicated that at low stress, the true creep-activation energy of Sn-3.8Ag-0.7Cu and SnAgCu-0.1RE solder joints is close to the lattice self-diffusion activation energy, so the steady-state creep rates of these two solder joints are both dominated by the rate of lattice self-diffusion. While at high stress, the true creep-activation energy of Sn-3.8Ag-0.7Cu and SnAgCu-0.1RE solder joints is close to the dislocation-pipe diffusion activation energy, so the steady-state creep rates are dominated by the rate of dislocation-pipe diffusion. At low stress, the best-fit stress exponents n of Sn-3.8Ag-0.7Cu and SnAgCu-0.1RE solder joints are 6.9 and 8.2, respectively, and the true creep-activation energy of them both is close to that of lattice self-diffusion. At high stress, it equals 11.6 and 14.6 for Sn-3.8Ag-0.7Cu and SnAgCu-0.1RE solder joints, respectively, and the true creep-activation energy for both is close to that of the dislocation-pipe diffusion. Thus, under the condition of the experimental temperatures and stresses, the dislocation climbing mechanism serves as the controlling mechanism for creep deformation of Sn-3.8Ag-0.7Cu and SnAgCu-0.1RE solder joints. The creep values of Sn-3.8Ag-0.7Cu and SnAgCu-0.1RE solder joints are both controlled by dislocation climbing. Dislocation glide and climb both contribute to creep deformation, but the controlling mechanism is dislocation climb. At low stress, dislocation climbing is dominated by the lattice self-diffusion process in the Sn matrix and dominated by the dislocation-pipe diffusion process at high stress.     

Electrodynamics of rotating relativistic electron beams

On the basis of the Minkowski formulation, this paper discusses the basic laws governing the small-signal fields propagated along an electron beam which is rotating around its axis with constant angular frequency of rotation and drifting in the axial direction at constant relativistic velocity. In the first preliminary section are described the dc conditions for getting a stable relativistic electron beam in the presence of neutralizing ions with arbitrary number density and externally applied static magnetic field. Then, after a brief discussion of the ac-field equations, the constitutive relations for small-signal fields are obtained in both the laboratory frame, which is assumed to be an inertial frame, and the rest frame of the electron beam, which is not an inertial but a rotating frame. The rotating relativistic electron beam is found to be a nonuniformly moving dispersive medium or, more specifically, an inhomogeneous bianisotropic medium with space and time dispersion. With the use of the constitutive relations derived above, the following sections consider the energy and momentum for the small-signal fields, and their conservation relations, together with their transformation laws between the laboratory frame and the rest frame of the electron beam. Our discussion includes, as the special cases, all the important cases of an ion-neutralized or axially confined beam and the Brillouin beam.     

Surface-wave probe for measuring electron densities in a gaseous plasma

A dielectric rod enveloped in gaseous plasma can act as a supporting structure for electromagnetic surface waves. The dielectric constant of the plasma and hence the electron number density in the vicinity of the rod may be determined from measurements of the phase-change coefficient of the EH11 mode supported by the plasma-clad rod. Measurements of radial density distribution have been carried out in an unmagnetised argon afterglow plasma at 35Gc/s and compared with double-probe measurements.     

General relations for nonperiodic bandlimited signals in three-dimensional electron flow

Relations for bandlimited signals in electron flow are presented that may be considered as a generalisation of power relations for sinusoidal signals. Inequalities defining limiting values for the power densities are obtained when signals exist in three frequency bands only which correspond to the frequencies in a parametric amplifier.     

Mean electron energy in a CO2 laser plasma

It is argued that measurements made using microwave radio-metric techniques represent a true mean electron energy for the CO2 laser plasma. They agree well with some other experimental values, and excellently with a theoretically calculated value.     

Measurement of electron attachment processes in a high-temperature plasma

An experimental technique has been developed for measuring rate constants of electron attaching reactions as well as ion-molecule reactions in plasma at 2000-3000°K. Reaction product ions are mass analyzed and rate constants are obtained from plots of the collected ion current. The rate constant for O^-formation from N2O varies from about 3 to 9×10^-9cm³/s over the temperature range of 2400-3000°K while the rate constant for F^-formation from SF6varies from 2.8 to 4×10^-10cm³/s for temperatures from 2775 to 3000°K. A brief survey of experimental techniques for measuring electron attachment rate constants at lower temperatures is also given, together with a comparison of these rate constants and present high-temperature values.     

Waveguide modes of a warm drifting uniaxial electron plasma for large drift velocities

The dispersion relation for guided waves in a warm drifting uniaxial electron plasma is derived for the case of large drift velocities using relativistic transformations. The phase characteristics of the "fast," "slow," and "waveguide" waves are presented and compared with the results of the nonrelativistic treatment. Significant differences are noted for small values of the normalized empty guide cutoff frequency and large drift velocities.     

Development of a high-selectivity process for electron cyclotron resonance plasma etching of II-VI semiconductors

The erosion rate of resist during electron cyclotron resonance (ECR) plasma etching of II-VI semiconductors is the limiting factor for the selectivity (values range from 5:1 to 10:1). We have measured the erosion rates of AZ 1529, a commercially available diazonaphthoquinone (DNQ) novolak photoresist, under plasma conditions optimized for etching of the underlying semiconductor and have developed an in-situ technique to “harden” the resist by exposing it to an argon-only ECR plasma. A subsequent standard plasma process can then be used to etch the II-VI material, thereby achieving selectivity values greater than 50:1.     

Langmuir-probe measurement of electron temperature in a flowing high-density plasma

Measurements with cooled double probes in a propane-air flame show that the measured electron temperature and the floating voltage of the probes can be strongly affected by variation of the probe temperature. Simple theoretical considerations indicate that these effects arise from cooling of the plasma electrons by collisions with cold molecules in the hydrodynamic boundary layer surrounding the probe.     

Constitutive and damage model for a lead-free solder

A unified creep plasticity theory with damage is presented for a lead-free solder. The damage is caused by microcracking both inside grains and along grain boundaries and increases with cyclic loading and creep. The Mura theory of microcrack nucleation was used to model the microcrack formation, while the percolation theory was used to characterize the damage such microcracking caused to the mechanical performance of the solder. The model is materials science based and is capable of application to solder joints of different sizes. It is also cast within the framework of phenomenological damage mechanics and is therefore convenient for implementation into commercially available computational software package. The theory was used to model isothermal experimental data for a eutectic solder 96.5Sn-3.5Ag, and good agreement was achieved.     

Cd recombination laser in a plasma generated by an electron beam

Laser action was obtained in the 1.40, 1.43, and 1.65 μm lines of CdI following electron-ion recombination in a plasma generated by an electron beam. Lasing does not occur during the excitation pulse due to the electron impact population of the laser lower levels. In this plasma, supercooling of the electrons is achieved under stationary conditions, and efficient CW recombination laser action might also be possible on lines in which the lower level is not significantly populated by electron collisions. Seven new infrared laser lines in CdII are also reported.     

Waves on an electron beam in vacuo and in a plasma

The problems of wave propagation on a cylindrical electron beam in vacuum and in a plasma background are examined in an exact treatment, i.e., from Maxwell's equations, including relativistic effects. It is shown that certain ambiguous features of the more usual nonrelativistic quasistatic analysis are thereby resolved.     

High-resolution laser interferometer for measurement of electron density in transient plasma

A laser interferometer of the Mach-Zehnder type based on the use of a single-mode frequency-stabilised He-Ne gas laser, 6329 ? in wavelength and with 100 ?V output, has been used to measure accurately electron densities in the range 1014?1015cm?3 in a transient mercury-vapour plasma. An `amplitude? (intensity) modulation system is employed in order to obtain a wide dynamic range. The interferometer system is mounted on a massive movable table in order to obtain the spatial distribution of electron density by means of sequential discharges. The experimental results show clearly that there are definite time delays between the peak of current in the discharge and the maximum value of the (average) electron density. The results are in good agreement with the values of electron densities obtained by the extrapolation from microwave measurements.     

Measurements of electron density and plasma current distributions in Tokamak plasma

A submillimeter-wave, phase-modulated polarimeter/interferometer is used for simultaneous time-dependent measurement of line-averaged electron density and poloidal field-induced Faraday rotation along chords of the plasma column in ISX-B tokamak. Heterodyne detection and hollow dielectric waveguide are utilized to achieve the high sensitivity required for the multichord experiment. A data analysis code has been developed to reconstruct the asymmetric distributions of plasma density. The validity of the code is examined, and the result shows good agreement with density profiles measured by Thomson scattering.     

微管靶等离子体电子温度密度的空间分布

用高功率激光加热微管靶,观察到在软X光波段的Mg~(+10)能级粒子数反转.对微管靶作的二维诊断,得到了维管靶等离子体电子温度和密度的空间分布.