Sensitivity of Homogeneity Mapping of Dielectric Wafer Using Millimeter Waves

A plane electromagnetic wave normally falling on a surface of a dielectric plate has been considered to investigate the sensitivity of the dielectric constant homogeneity mapping in the dielectric wafer by measuring the phase and/or the amplitude of the millimeter wave reflected from or transmitted through it. Measurement conditions at which the highest sensitivity might be achieved are established. The sensitivity at Fabry-Perot resonance conditions as well as at frequency shifted from resonance has been considered.     

Surface plasma waves over bismuth-vacuum interface

A surface plasma wave (SPW) over bismuth-vacuum interface has a signature of mass anisotropy of free electrons. For SPW propagation along the trigonal axis there is no birefringence. The frequency cutoff of SPW lies in the far infrared region and can be accessed using free electron laser. The damping rate of waves at low temperatures is low. The surface plasma wave may be excited by an electron beam of current ∼100 mA propagating parallel to the interface in its close proximity.     

Production of high quality shocks for equation of state experiments

In this paper we describe the quality requirements that a shock wave must fulfil to make equation of state (EOS) measurements possible: planarity, no-preheating and stationarity of the shock. Experimental measurements have been performed at the Max Planck Institut für Quantenoptik (Garching). We also present simple analytical models that allow to verify shock stationarity and absence of preheating. Received 17 June 2002 Published online 21 January 2003 RID="a" ID="a"e-mail: batani@mib.infn.it RID="b" ID="b"Present address: Pro-beam, Behrinsta?e 6, 85152 Planegg b. München, Germany. RID="c" ID="c"UMR 7605     

A Global Solution to a Two-dimensional Riemann Problem Involving Shocks as Free Boundaries

We present a global solution to a Riemann problem for the pressure gradient system of equations.The Riemann problem has initially two shock waves and two contact discontinuities. The angle between the two shock waves is set initially to be close to 180 degrees. The solution has a shock wave that is usually regarded as a free boundary in the self-similar variable plane. Our main contribution in methodology is handling the tangential oblique derivative boundary values.     

Entropy Production and Admissibility of Shocks

In shock wave theory there are two considerations in selecting the physically relevant shock waves.There is the admissibility criterion for the well-posedness of hyperbolic conservation laws.Another consideraztion concerns the entropy production across the shochs.The latter is natural from the physical point of view,but is not sufficient in its straightforward formulation,if the system is not genuinely nonlinear.In this paper we propose the principles of increasing entropy production and that of the superposition of shocks.These principles arc shown to be equivalent to the admissibility criterion.     

Nondestructive Material Homogeneity Characterization by Millimeter Waves

Millimeter wave bridge technique for nondestructive material homogeneity characterization is described. The idea of this technique is the local excitation of millimeter waves in testing material and the measurement of the transmitted amplitude and phase in it different places. Some results of the homogeneity measurements for the dielectric substrates are presented.     

Parametric Transducers for the Advanced Cryogenic Resonant-Mass Gravitational Wave Detectors

It is shown that a large improvement in liquid helium and ultra-cryogenically cooled resonant-mass gravitational wave detectors can be achieved through improved parametric transducers using either low loss sapphire dielectric resonators or niobium re-entrant cavities. Performance is analysed in relation to the existing resonant bar antenna Niobe and to massive spherical detectors. Applied to Niobe, a millisecond burst sensitivity of order 10^–20 can be achieved, corresponding to a spectral strain sensitivity of 2 × 10^-22 Hz with a 50 Hz bandwidth. Applied to an ultra-cryogenic 117 tonne spherical detector made from CuAl, a spectral strain sensitivity of better than 2 ×10^-23/ Hz with a bandwidth of order 100 Hz can be achieved, which is close to the quantum limit. This sensitivity is comparable to that of advanced interferometer detectors at this frequency.     

An Optimum Sectional Waveguide Taper for Quasioptical Transmission Lines

The paper considers an optimum sectional waveguide taper (OSWT) which at a shortest length of the transition region provides nearly adiabatic propagation of the fundamental mode between circular, widely different in diameter quasioptical transmission lines of class hollow dielectric waveguide (HDW). Derived as a consequence of coaxial circular-horn sections, the OSWT offers all the advantages of a simple geometry and lends itself to simple fabrication techniques. The relationships among the critical geometrical parameters and the loss calculation formulae are presented. The comparison studies show that even at a few sections, the OSWT is almost as good in performance as the parabolic taper, but the OSWT is much better from a mechanical viewpoint. And compared to the ordinary linear taper, the OSWT allows essential cut in length and loss with the broadbandness kept. The HDW-based four-sectional OSWT has been fabricated and tested in a quite broad wave range 2,5-8 mm. The testing results lend a good support to the analytical formulae lying at the basis of the design software.     

左右手系材料界面处全反射行为的特性

基于电磁场理论，推导了左右手系材料界面处发生全反射时的物理特性，分析了相位变化情况.提出利用左右手系材料构成周期性结构，观测全反射时介质中隐失波干涉的实验设想，并从理论上计算了干涉条纹的分布. 关键词： 左手材料 负折射率 全反射 隐失波     

激光等离子体的电子温度对Thomson散射离子声波双峰的影响

通过对不同激光条件产生的等离子体进行Thomson散射实验诊断，发现在距靶面为150 μm的临界密度面内，离子声波双峰强度出现明显的不对称性，而且强峰的位置发生了转移：当等离子体的电子温度较高时，强峰出现在短波方向；当等离子体电子温度较低时，强峰出现在长波方向.光的拉曼散射效应对应地解释了离子声波的双峰结构、双峰强度不对称性及强峰出现的位置.建立了光的拉曼散射与电子的Thomson散射的对应关系.