摘要:

Ferroelectric domain configurations and other crystal imperfections in tin‐modified PZT ceramics were directly observed by high‐resolution transmission electron microscopy. Specimens in both the unpoled and poled conditions were examined. 90° domain walls appear to predominate, and typical examples are given for both cases. The implications of this direct method for development of ferroelectric devices are outlined.

ISSN:0021-8979    

DOI:10.1063/1.1662141

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Experiments have been carried out to investigate the processes leading to the generation of intense microwave signals, resulting from the nonadiabatic motion of an electron beam along a rippled magnetic field. The observations made are consistent with an instability occurring when phase‐matching conditions for a cyclotron wave on the beam and a waveguide mode are satisfied. The injection of the beam through the rippled field then serves the primary purpose of converting some of the electron motion from the parallel to the perpendicular sense. The microwave signal is maximized when this conversion is most efficient. Measurements are reported of diamagnetism, beam drift currents, and the microwave power and frequency spectrum. The results presented are interpreted as far as possible using existing theories.

ISSN:0021-8979    

DOI:10.1063/1.1662142

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The magnetic fields on the surface produced by a buried current‐carrying cable of finite length are considered. A homogeneous half‐space model of the earth and quasistatic conditions are assumed. The cable is grounded at its end points and oriented at an arbitrary angle to the interface. While, in general, numerical integration is required, the low‐frequency limit may be treated analytically. Small cable tilts are shown to modify the direction of the surface field but not the magnitude. The results have possible application to uplink communication and radio location of trapped miners.

ISSN:0021-8979    

DOI:10.1063/1.1662143

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The characteristics of electromagnetic surface waves supported by a plane interface separating a semi‐infinite region of free space from another semi‐infinite region consisting of a background plasma permeated by a neutralized beam streaming parallel to the interface are investigated for the case in which the wave is progressing either in, or opposite to, the direction of the beam. As compared to the case of a stationary plasma, the surface wave has new branches and drastically different characteristics. For the case of waves progressing opposite to the direction of the beam, there are backward‐wave regions as well as regions of instability if the beam is sufficiently strong. These regions of instability occur below the plasma frequency. In general, there are two frequency ranges of instability in which the surface wave undergoes traveling wave amplification in the direction of the stream. The wave amplification characteristics are studied and their dependence on the number density of the beam relative to the background plasma is examined.

ISSN:0021-8979    

DOI:10.1063/1.1662144

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Mass spectrographic studies have been conducted on the positive ions and neutral species in glow discharges containing 1.0% each of SO2and CO in helium and also 1.1% each of SO2and CO2in helium. Ion species observed in these mixtures included S+, SO+,SO2+,O+,O2+C+, CO+, andCO2+with lesser amounts ofSO3+,[CO]2+, SCO+, and [SO·CO]+(orCS2+). The functional dependencies of the various ion and neutral species on pressure and discharge current for He&sngbnd;SO2&sngbnd;CO mixtures were consistent with the interpretation that CO reacted with the SO formed in the discharges to produce CO2and sulfur. Measurements in He&sngbnd;SO2&sngbnd;CO2mixtures also indicated the removal of SO2through the formation of CO2and S.

ISSN:0021-8979    

DOI:10.1063/1.1662145

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The secondary electron emission coefficient &ggr; for gas‐covered Au, Mo, and CuBe surfaces was determined in the energy range 0.3–22.4 keV for incident ions as follows: H+, C+ 1 → 6, Al+ 1 → 10, Cu+ 1 → 9, Ta+ 1 → 3. Energetic highly charged ions produced by a Nd laser beam focused on solid targets in vacuum were allowed to impinge on a metal target. The electrons ejected were collected and the current measured. Potential ejection is dominant over kinetic ejection in this energy range. The Parilis‐Kishinevskii theory of secondary electron emission, based primarily on ionization of metal target atoms with subsequent recombination through an internal Auger process, and the present experimental results for low charge numbers (n≤ 3e) and high mass (A≥ 27) are only in qualitative agreement. For high charge numbers (n≥ 4e) or low mass (A≤ 12), there is no agreement.

ISSN:0021-8979    

DOI:10.1063/1.1662146

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The electron backscattering properties of clean Ge(100), GaAs(100), GaAs(111)B, Ga70Al30As(111)B, GaP(111)A, and Si(100) surfaces are studied in the 0.08–3‐keV range at pressures below 50 pTorr. The kinetic energy distribution and the backscattered yield &eegr;(Er, Ep) are measured by ac and dc retarding field methods. The data on backscattering is used to estimate the influence of high‐energy backscattered electrons on the resolution of Si and GaAs transmission secondary electron multipliers. The results show that the degradation in the modulation transfer function at low spatial frequencies is approximately 8% for GaAs and less than 4% for Si.

ISSN:0021-8979    

DOI:10.1063/1.1662147

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The energy distribution of electrons emitted from negative electron affinity (NEA) GaAs: Cs&sngbnd;O has been calculated for various doping concentrations (1 × 1018−2 × 1019cm−3) and work functions (0.95–1.15 eV). It has been assumed that electrons to be emitted have thermalized at the bottom of the conduction band when they reach the surface bent‐band region. The energy distribution of the electronsreachingthe surface is determined by their interactions in the bent‐band region and is calculated from a solution of the Boltzmann transport equation. Multiplication of this distribution with an energy‐dependent transmission probability for the surface barrier yields the energy distribution of theemittedelectrons. The width of the bent‐band region, and thus the doping concentration of the emitter material, has a significant influence on the shape and width of the distribution and on its location on the energy scale, while the work function mainly affects the magnitude of the distribution. Measured half‐widths of the energy distributions from NEA GaAs photocathodes and cold cathodes are in good agreement with the calculations.

ISSN:0021-8979    

DOI:10.1063/1.1662148

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The particle production from low‐current (0.48‐A short circuit) nominally resistive break arcs between palladium‐gold contacts have been examined under ``clean'' and ``activated'' conditions. Particles produced in air and in dry nitrogen were measured using a condensation particle counter which detected particles of approximately 20‐Å diameter and larger, with a sensitivity limit of 25 particles cm−3of air corresponding to about 5000 total particles per break arc under our experimental conditions. The operation of the relay at 15 Hz produced large numbers of particles, the production of which was nonlinear with the repetition rate, and therefore the experiments were carried out at lower cycle rates (<5 Hz). Under these conditions it was observed that after an initial period of about 500 operations, short (<10 &mgr;sec) break arcs did not produce any detectable particles. Particles were detected for arcs of greater than 30‐&mgr;sec duration with the number of particles increasing with the arc duration. Activation of relay contacts with consequent production of particles was found to take place in both filtered air and dry nitrogen showing that the activation process does not require the presence of oxygen or atmospheric particles.

ISSN:0021-8979    

DOI:10.1063/1.1662149

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The thermoelectric power and resistivity of annealed copper films have been measured. From the thermoelectric power values at the minimum in resistivity and the corresponding temperature coefficient of resistance, the calculated values of the energy dependence of the mean free path of conduction electrons and the Fermi surface area are −0.21 and −1.43, respectively.

ISSN:0021-8979    

DOI:10.1063/1.1662150

出版商:AIP    

年代:1973

数据来源: AIP