摘要:

Integropartial differential equations of the linear theory of nonlocal elasticity are reduced to singular partial differential equations for a special class of physically admissible kernels. Solutions are obtained for the screw dislocation and surface waves. Experimental observations and atomic lattice dynamics appear to support the theoretical results very nicely.

ISSN:0021-8979    

DOI:10.1063/1.332803

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The image formation and the resolution of a self‐contained electrophoretic x‐ray imager have been investigated. The electrophoretic suspension contained pigments and counterions, ionic surfactants, and extraneous charges. Rate equations have been formulated to describe the transport properties of the ionic surfactants from the low to high field regions. The electrical transport properties of the electrophoretical suspension were investigated in relation to x‐ray image formation using three different modes of operation: the pulse, the biased‐pulse, and the universal modes. The reflectance versus charge curves of the x‐ray images were qualitatively explained. Both negative‐ and positive‐mode x‐ray images of 22×22 cm2have been demonstrated with two different electrophoretic suspensions. The imager can achieve x‐ray images of high resolution and large area at the same time.

ISSN:0021-8979    

DOI:10.1063/1.332804

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Wave‐number and frequency spectraS(k,&ohgr;) associated with spontaneous electrostatic fluctuations in a high‐density (5×1021m−3) current‐driven plasma are measured using forward CO2‐laser scattering with homodyne detection. Scattering measurements during the quiescent plateau phase of the discharge show fluctuation levels several orders of magnitude above the thermal level withk−4and &ohgr;−2spectral amplitude dependences. The fluctuations are found to be isotropic in a plane transverse to the magnetic axis withS(k∥,&ohgr;)≪S(k⊥,&ohgr;). The scattering apparatus is also shown to be a valuable diagnostic tool for basic studies of plasma current transport across magnetic field lines. In fact, a clear correlation is observed between the appearance of strong fluctuations and the rapid current penetration during fast plasma current reversal experiments. Finally, cw scattering results are used to find a set of experimental conditions suitable for the measurement of the ion temperature using a CO2pulsed scattering system.

ISSN:0021-8979    

DOI:10.1063/1.332805

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The collision half‐width for theR(0) absorption line of the &ngr;3band of methane has been determined as a function of temperature with nitrogen and carbon dioxide as the broadening gases. The measurements were made in the temperature range from 300 to 1000 K with broadening gas pressures in the range from 5 to 15 psi (absolute). Methane partial pressures sufficient to produce approximately 60% absorption at line center for each condition were used. The line spectrum was produced with a Laser Analytic LS‐3 tunable diode laser spectrometer. A best‐fit Voigt profile to the experimental line shape was used to determine the broadening which is characterized by the collisional or Lorentz half‐width.

ISSN:0021-8979    

DOI:10.1063/1.332806

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The effect of iron on the uniformity of the field produced by an axisymmetric thick solenoid is considered. Using a Fourier series approach, an exact solution for the vector potential A is found and from this the magnetic induction B is derived. The results are compared with those obtained from previous approximate methods.

ISSN:0021-8979    

DOI:10.1063/1.332807

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The theory of linear systems is used to derive the potential and electric field in distance space in a cylindrical polarization/depolarization electret chamber. General solutions for the near, intermediate, and far regions are given and their domains of convergence discussed. On the axis of the chamber the solutions for the electret surface are equal to those obtained from Gauss’s and Kirchoff’s laws, and at large distances from the surface to those obtained from the introduction of a dipole layer model.

ISSN:0021-8979    

DOI:10.1063/1.332808

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

An extensive set of Kerr electro‐optic field mapping measurements are reported for highly purified water over the temperature range of 8.8–29.5 °C. The Kerr constant is independent of temperature over this range and equalsB&bartil;3.4×10−14m/V2. Pulsed high voltages up to 140 kV across parallel cylindrical electrodes with a 1‐cm gap are applied on millisecond time scales. For early times, the measured results agree with the space‐charge‐free electric field distribution while for times greater than 500 &mgr;sec, there is significant space‐charge distortion due to positive charge injection.

ISSN:0021-8979    

DOI:10.1063/1.332809

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

High voltage Kerr electro‐optic field mapping measurements in highly purified water show significant field distortions due to injected positive space charge over the temperature range of 8–25 °C using parallel plane stainless steel electrodes stressed to average field strengths up to 150 kV/cm. The net space charge was always positive with density of &bartil;2 C/m3which is about 40% of the background value of charge density of thermally generated hydronium and hydroxyl ions. Because measurements only showed a net positive space charge, a unipolar drift dominated conduction model was developed where positive charge would migrate in an ohmic medium. This model predicts the observed propagating charge front, electric field enhancement at the noncharge injecting electrode, and field decrease at the charge injecting electrode. The time of flight of positive charge between electrodes gave an estimate of the positive ion mobility of &mgr;&bartil;4×10−7m2/(V s) which is inbetween the values of the hydronium ion mobility measured at low voltages and the electrohydrodynamic mobility which accounts for fluid convection effects due to the Coulombic force putting the fluid into motion. The dielectric relaxation time atT&bartil;8 °C (&tgr;&bartil;320 &mgr;sec) measured at low voltage was much less than the measured charge transport time between electrodes, &tgr;mig&bartil;2 msec, so that the calculated effects of space charge were much less than measured because the charge relaxes quickly as it migrates. It was found that a dielectric relaxation time of &tgr;&bartil;1.6 msec would provide a good fit between analysis and experiments.

ISSN:0021-8979    

DOI:10.1063/1.332810

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

We describe the magnetic design problems involved in the realization of the permanent magnet undulator ‘‘Nouvel Onduleur pour l’Etude du Laser (NOEL)’’currently being used for the free electron laser experiments on the storage ring ACO. The undulator has been compensated for the magnetic imperfections of the magnet elements used for its construction. Each pole piece was made from two elements so that we could cancel out the transverse field errors. Each undulator pole was selected from a two‐dimensional magnet distribution graph which was drawn with the results of a set of Hall‐probe measurements. Magnetic measurements of the assembled undulator as well as the first experiments on the ACO storage ring indicate that the method has been successful.

ISSN:0021-8979    

DOI:10.1063/1.332811

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

An analysis is presented of the spectrum radiated by an electron beam passing through a magnetic wiggler in a rectangular waveguide using a coupled‐mode approach. The noise power radiated into each mode of the waveguide is calculated. In the limit of a highly overmoded waveguide and large relativistic parameter, the total emitted spectrum approaches that of a beam in free space. The radiation formulas are greatly simplified for a weak magnetic field.

ISSN:0021-8979    

DOI:10.1063/1.332785

出版商:AIP    

年代:1983

数据来源: AIP