摘要:

The effects of heating on both the reflectivity and layered structures of Mo/Si and Mo‐silicide/Si (MoSi2/Si and Mo5Si3/Si) multilayers were evaluated. The Cu‐K&agr;x‐ray reflectivity and the periodic length of the Mo/Si multilayer markedly decreased after heating at above 300 °C, while those of the Mo‐silicide/Si multilayers changed only slightly even after heating up to 600 °C. Transmission electron microscopy observations revealed markedly less thermally induced deterioration in the Mo‐silicide/Si multilayers than in the Mo/Si multilayer, indicating that Mo‐silicide/Si multilayers have better heat resistance than Mo/Si multilayers. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359698

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Free electron laser dynamics is characterized by the interplay between bunching and emission processes. The first mechanism can be quantitatively specified in terms of the so‐called bunching coefficients, which determine the degree of the bunching at the fundamental and higher harmonics. We numerically solve the Liouville equation, which rules the longitudinal phase‐space dynamics, and evaluate the bunching coefficients and associated harmonic generation. We develop a semianalytical method to study the harmonic generation and evolution in free electron laser oscillators. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359699

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

For both transverse magnetic and transverse electric modes, the governing equations for the guided‐guided wave interaction in a dielectric thin film waveguide which is etched with a cosinusoidal surface corrugation have been developed by using a quasioptical technique. These governing equations are used to investigate the effect of the phase shifter on the characteristics of the distributed feedback laser. Phase shifters either at the center or at the ends of the laser eliminate the gain degeneracy and make the power distribution inside the laser more uniform. When the amount of phase shift is appropriately chosen, the gain margin increases and reaches a maximum value. The roles of the other parameters in achieving a single‐mode operation for the laser have been investigated by means of numerical examples. It has been found that the characteristics of the distributed feedback laser with phase shifters are quite similar for both transverse magnetic and transverse electric modes. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359700

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report on the optical reflective properties of the planar texture of cholesteric liquid crystal reflective displays. The reflecting liquid‐crystal medium is partitioned into many distinguishable domains, each of which is characterized by its local dielectric anisotropy. Such a multidomain cholesteric liquid crystal is made bistable by either dispersing a low concentration of polymer or by treating the cell substrate surfaces, both of which affect the domain alignment. Both types of cells result in a bistable colorful reflective display. We determine the role that the polymer network and surface alignment has on the reflective properties in regard to their photometric and colorimetric properties as a function of viewing angle using both collimated and diffuse illumination. Both the polymer network and surface anchoring have the effect of distributing the orientation of the cholesteric helix axes about the cell normal. Theoretically we characterize these cells by this distribution. Our goal is to properly model both types of display cells so as to quantitatively elucidate their distinguishing features. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359701

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A simple dispersion equation for surface thermal waves propagating along a solid surface covered with a thin film of higher thermal conductivity is presented. It is shown to describe well phase measurements with a photothermal microscope carried out on metal films on glass substrates. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359702

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The electrohydrodynamic (EHD) instability in planar geometry was observed using gallium as the working fluid. Electric fields in the range of 0.12–0.26 MV/cm were applied in pulse durations up to 14.4 ms. The instability of the gallium surface was observed using a box camera and pulsed backlighting. The measured wavelengths of the instability ranged from 1.2 to 17.0 mm, consistent with theoretical predictions provided a field enhancement factor of 1.5 is assumed on the meniscus of the gallium. A transverse magnetic field of about 0.6 T was found to completely dampen the instability along the magnetic field at an applied electric field of 0.2 MV/cm; the transverse direction was unaffected. This result puts limits on the usefulness of an EHD ion source in magnetically insulated diodes for inertial confinement fusion studies. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.360697

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Phosphorescent light emission was investigated upon irradiation of WF6/H2/noble gas (Ar, Kr, Ne, Xe) mixtures by ArF excimer laser. The continuous, broadband phosphorescence emission originates from excited tungsten clusters. The phosphorescence ceased with increased Xe and H2concentrations. Xe inhibits the formation of tungsten clusters and H2quenches the phosphorescence. The H2quenching rate and the unperturbed phosphorescence lifetime were determined to be 2.8×104mbar−1 s−1and 23 &mgr;s, respectively. The intensity dependence of phosphorescence on the WF6partial pressure shows a rising part, then a declining part, and finally an increasing part again. It was shown that the declining part can be interpreted by scattering of the emitted phosphorescence. The phosphorescence intensity was dependent on the noble gas/H2concentration ratio. This effect was explained in terms of the thermal conductivity of the WF6/H2/noble gas mixture, which influences the lifetime of the activated subfluorides and, thus, the cluster formation and growth rate. The intensity of the laser beam had a nonlinear effect on the phosphorescent light intensity due to the nonlinearly coupled photolytical steps of WF6and of the subfluorides. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359703

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Atmospheric pressure plasmas can be used to provide a vacuum‐atmosphere interface as an alternative to differential pumping. Vacuum‐atmosphere interface utilizing a cascade arc discharge was successfully demonstrated and a 175 keV electron beam was successfully propagated from vacuum through such a plasma interface and out into atmospheric pressure. Included in the article are a theoretical framework, experimental results, and possible applications for this novel interface. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359704

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The statistics of microdischarges crossing the air gap between conductors and insulating polymers have been measured. Long tails of pulse‐amplitude and pulse‐time‐separation distributions have been observed and their nature examined. The long tails of time distributions followed quasiexponential behavior while the long tails of amplitude distributions satisfied a fractal power law. The transformation relations between both sets of statistics have been determined and their consequences discussed. The clearly resolved fractal long tails of amplitude distributions have not been observed so far and represent a new result in the statistical studies of microdischarges. Also the determined transformation relations between time and amplitude statistics bring a new insight into the studied phenomenon. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359705

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The magnitude and relative phase of the rf magnetic flux density has been measured as a function of radial position using a magnetic (B‐dot) probe in an inductively coupled low pressure argon discharge driven at 13.56 MHz. The spatial variation of the rf electric field and the discharge current density were determined from the probe measurements and are compared at gas pressures of 3, 30, and 300 mTorr for a fixed discharge power of 50 W and at discharge powers of 21, 50, and 103 W for a fixed gas pressure of 30 mTorr. In the active zone near the induction coil where the rf field is strong, the electron rf drift velocity derived from the B‐dot data and Langmuir probe measurement was found to be considerably less than the electron thermal velocity even at the lowest argon pressure. For an axially symmetric inductive discharge, as is found in many applications, a two‐dimensional magnetic probe measurement with space and phase resolution is necessary to correctly infer the rf electric field and the discharge current density distribution. ©1995 American Institute of Physics.

ISSN:0021-8979    

DOI:10.1063/1.359706

出版商:AIP    

年代:1995

数据来源: AIP