摘要:

The linear theory of electrostatic electron cyclotron resonance maser (EECRM) is given in this paper. Starting from the fundamental concept, we obtained the perturbed equation of relativistic electron motion in an electrostatic centrifugal system, and the dispersion equation for both TEmnand TMmnmodes of the EECRM have been derived with detailed discussion for the infinitely thin beam layer. The nonrelativistic case has also been studied. Digital calculations show that the dispersion curves of the EECRM are similar in shape to that of the conventional electron cyclotron resonance maser (MECRM) and the magnitude of growth rate of the EECRM is comparable with that of MECRM. Although the dispersion equation of EECRM contains a special kind of singularity [&ohgr;−k∥v∥−(m±(2−&bgr;2⊥)1/2) &ohgr;0=0], the relevant instability within the parameter region of our calculations in this paper has not yet been found; this problem remains to be studied in the future.

ISSN:0021-8979    

DOI:10.1063/1.336794

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Digital image analysis (DIA) is applied to extract various types of physical information from an image of high‐order structures in polymer systems observed under an optical microscope. DIA can be applied to analyze the pattern formation phenomena in general. Various numerical operations in real and wave‐number space make it possible to extract physical information unobtainable by other methods, such as the use of light scattering. The possibility of valuable operations in DIA are presented with examples. The technique itself is useful not only in polymer systems but also in various fields such as studies of liquid crystals, biological systems, metals, and pattern formation in solution or chemical reaction.

ISSN:0021-8979    

DOI:10.1063/1.336795

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Spectra of highly ionized praseodymium and dysprosium recorded from the Texas tokamak (TEXT) plasma have been analyzed in the 50–250‐A˚ range. The spectra contain high‐intensity continuum bands in the region below 100 A˚ and bright individual lines above this wavelength. Lines of highly ionized praseodymium and dysprosium have been identified. The highest ionization state reached in the 1‐keV central electron temperature tokamak plasma was Cu i‐like Pr xxxi. The composition of the bands is explained in terms of a new theoretical approach developed to treat large unresolved transition arrays. The brightness of the continuum is compared with that of intense spectral lines emitted in the same wavelength range.

ISSN:0021-8979    

DOI:10.1063/1.336744

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

For a multilayered random medium with a laminar structure a Green’s function approach is introduced to obtain the emitted intensity due to an arbitrary point source. It is then shown that the approach is applicable to both active and passive remote sensing. In active remote sensing, the computed radar backscattering cross section for the multilayered medium includes the effects of both volume multiple scattering and surface multiple scattering at the layer boundaries. In passive remote sensing, the brightness temperature is obtained for arbitrary temperature profiles in the layers. As an illustration the brightness temperature and reflectivity are calculated for a bounded layer and compared with results in the literature.

ISSN:0021-8979    

DOI:10.1063/1.336745

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A liquid‐crystal window has been considered as an optical shutter to control solar energy. Transmittance of dynamic‐scattering, twisted‐nematic, and phase change guest‐host (PCGH) cells having 6, 9, and 12 &mgr;m thicknesses has been measured and compared. A PCGH cell with black dye exhibits an anomalous transmission dip in the region of cholesteric to nematic or vice versa phase transformation for incident incoherent light of &lgr;<500 &mgr;m. We attribute this dip to voltage‐induced inhomogeneities generated during the phase transition. Transmittance controllability as high as 50% has been achieved with a 6‐&mgr;m‐thick PCGH cell with one polarizer. A comparison of the transmittances of the three types shows that PCGH material is a suitable candidate for large size window fabrication.

ISSN:0021-8979    

DOI:10.1063/1.336746

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We derive the minimum requirements for super‐radiant gamma‐ray emission by applying the semiclassical theory of coherent spontaneous emission to the case of nuclear transitions in a crystal host. We find that, if a pure sample of a storage isomer can be rapidly transferred into an inverted population for a recoilless transition, less than 1013nuclei should suffice for an experimental demonstration of nuclear super‐radiance.

ISSN:0021-8979    

DOI:10.1063/1.336747

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

An anomalous phenomenon in the reflection and refraction of elastic waves on an interface between anisotropic crystals is analyzed. Due to the deviation of the ray (energy flow) direction from the wave normal for elastic waves in crystals, the domain of permissible incident angles splits into disjoint pieces for certain crystal cuts. This may lead to the existence of grazing angles at three different wave‐vector angles. The grazing angle is defined as the angle at which the ray vector of the incident wave is parallel to the interface. To clarify this interesting phenomenon, numerical calculations were made for the (001) plane of a Ni crystal, based on a calculational procedure developed previously for study of the reflection and refraction of elastic waves in crystals. For each of the two split domains of incident angle there appear two branches of the reflection coefficient for the slow quasi‐transverse wave corresponding to the same slowness surface. The value of the energy conversion of the incident wave into each of these reflected waves depends on the closeness of the direction of the displacement vector in these waves to the incident displacement direction.

ISSN:0021-8979    

DOI:10.1063/1.336748

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

An analysis of elastic waves is used to predict the final velocity of a flat metal plate that is struck by a second plate made of the same material. The loss of kinetic energy of the system is also calculated. Three examples corresponding to different mass ratios are considered, and it is seen that solutions for the ratio of the final velocity of the second plate to the initial velocity of the first plate, and for the ratio of the final kinetic energy to the initial kinetic energy, always lie between the solutions that correspond to perfectly elastic and perfectly inelastic collisions. One interesting result is that rebound never occurs, even if the mass of the projectile plate is less than that of the target.

ISSN:0021-8979    

DOI:10.1063/1.336749

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Prebreakdown ionization currents have been measured in SF6/N2and SF6/CCl2F2mixtures and respective gases by the steady‐state Townsend method over the range of reduced fields 70≤E/p20≤200 V cm−1 Torr−1. Relevant collisional processes to be included in the formulation of the current‐growth equation are briefly reviewed; electron detachment was accordingly neglected in the present current‐growth analysis. A numerical simulation has been carried out to quantify the errors expected when numerically retrieving the transport coefficients. A two‐parameter model, for which the initial currentI0is considered known, is found to give the best performance. Nonlinear regression analysis using Marquardt’s procedure is performed for evaluation of the ionization (&agr;), attachment (&eegr;), and effective ionization (&agr;¯) coefficients. The limit fields are obtained from the condition &agr;¯(E/p*)=0. The coefficients for the respective gases compare well with available data in the literature with the exception of the attachment coefficient in SF6which shows a more pronounced decrease than the general trend asE/pincreases. In the case of SF6/N2mixtures, good agreement is found for the effective ionization coefficients. The attachment coefficients do not saturate but rather increase with the SF6partial density. In SF6/CCl2F2mixtures, the variation of &agr;¯ is found to be nonlinear with the percentage mixture ratio. The resulting limit field exhibits small positive and negative synergistic effects, 6% and 3%, respectively; at 25% SF6content, the limit field is approximately 5% greater than that of pure CCl2F2. For SF6/N2mixtures, however, the limit field never exceeds that of SF6.

ISSN:0021-8979    

DOI:10.1063/1.336750

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A fast coaxial discharge line for the study of the electric breakdown of liquid hydrocarbons is described. It allows the simultaneous measurement of discharge current (up to 5 kA) and voltage (up to 50 kV) with nanosecond time resolution. The spark gap is of tip‐plane geometry. A detailed frequency analysis of the discharge and measurement circuits has been performed. Examples for the spark breakdown ofn‐hexane under a variety of conditions are presented.

ISSN:0021-8979    

DOI:10.1063/1.336751

出版商:AIP    

年代:1986

数据来源: AIP