Field induced reemission of electrons trapped in SiO2

A new form of hot electron injection and trapping in n-channel IGFET's is described, a necessary and sufficient condition for the emission of these trapped electrons is a reset pulse of negative gate and positive drain voltages. The effect of this trapping on device characteristics, reliability, and the proposed low-temperature operation of IGFET's is discussed.     

Hot electrons in MOS transistors: Lateral distribution of the trapped oxide charge

The spatial distribution (along the channel) of the oxide-trapped charge induced by hot electron injection in MOS transistors biased in saturation, is studied by means of two-dimensional device simulators. It is shown that hot electron trapping leads to a charge almost uniformly distributed over the region included between the points of channel pinch-off and zero transversal component of the surface electric field. A simplified analytic expression for the drain current in the triode operating region of the HE modified transistor is also given and found to be in reasonable agreement with experimental curves.     

A new low-loss mode in semiconductor magnetoplasmas

A new semiconductor plasma wave mode that can propagate with very little attenuation at frequencies smaller than the plasma collision frequency is described. The wave propagates at right angles to a dc magnetic field and may be used for modulation of lasers or for tunable filters in the microwave /millimeter wave region.     

Coupled-wave equations for propagation in stratified compressible magnetoplasmas

This letter deals with the propagation of coupled electromagnetic and electroacoustic waves in a magnetised compressible continuously stratified electron plasma. Some first-order coupled-wave equations are derived.     

Failure mechanisms of AlGaAs/InGaAs pseudomorphic hemt''s: Effects due to hot electrons and modulation of trapped charge

The reliability of AlGaAs/InGaAs pseudomorphic HEMT's has been investigated by means of thermal and hot-electron accelerated tests. Two commercially available devices have been tested, together with prototypes fabricated by a European supplier. Different failure modes have been observed after hot-electron testing, depending on the device type, i.e. (a) increase of drain current, I_D and threshold voltage, |V_T|, which can be attributed either to thermally-activated electron detrapping or to charge compensation by holes generated by impact ionization; (b) decrease of I_D at low drain to source voltages, V_DS, with the development of a kink in the output characteristics due to the generation of deep levels under the gate and subsequent electron trapping. In the former case, (a), hot carriers and/or high temperature storage only modulate the charge present on deep levels, leading to recoverable alterations of device characteristics. In the latter case, (b), the presence of additional deep levels under the gate leads to a permanent degradation. The link between the observed failure modes and the underlying physical mechanism is investigated by means of different techniques, and the main functional effects of the degradation modes are addressed.     

The first-order coupled differential equations for waves in inhomogeneous warm magnetoplasmas

The first-order coupled differential equation for waves in gyrotropic inhomogeneous warm magnetoplasmas are derived for the case where the plasma parameters N0(z), T0(z), v(z), and H0(z) vary in the z direction only. In this form they are well sited for solution on a digital computer by the Runge-Kutta method.     

Some instabilities of electromagnetic wave propagation through drifting semiconductor magnetoplasmas

The dispersion equation for electromagnetic wave propagation through drifting semiconductor magnetoplasmas has been derived for general orientations of carrier drift velocities and propagation vector relative to the dc magnetic field. This is used to show the possibility of two instabilities of wave propagation that are not diffusion limited to low frequencies.     

Hybrid Transmission Line for ECRH in the Helically Symmetric Experiment

The HSX oversized, mode-converting ECRH transmission line has been upgraded to a hybrid system to increase launched microwave power and reduce electrical arcing. Filtering of high-order, spurious modes ensures efficient coupling to a Gaussian beam for optimal electron heating. A Vlasov mode converter and two phase-correcting ellipsoidal mirrors convert the TE₀₂ gyrotron output mode to a symmetric, linearly polarized, microwave beam. A swappable twist reflector plate rotates beam polarization for 2nd-harmonic X-mode or fundamental O-mode ECRH. Long distances are traversed by coupling the beam to a dual-mode (TE₁₁?+?TM₁₁), smooth, circular cross-section waveguide. This system has been successfully tested without arcing for 50 ms pulses and over 100 kW of launched power. Analysis of the microwave beam for 50 kW, 2 ms microwave pulses reveals agreement with predicted beam shapes at two beam locations. The new system has also demonstrated increased plasma stored energy for ECRH plasmas with equal launched power.     

Recent Upgrades and Extensions of the ASDEX Upgrade ECRH System

The multi-frequency Electron Cyclotron Heating (ECRH) system at the ASDEX Upgrade tokamak employs depressed collector gyrotrons, step-tunable in the range 105?C140 GHz. The system is equipped with a fast steerable launcher allowing for remote steering of the ECRH RF beam during the plasma discharge. The gyrotrons and the mirrors are fully integrated in the discharge control system. The polarization can be controlled in a feed-forward mode. 3 Sniffer probes for millimeter wave stray radiation detection have been installed.     

Minimization of the Ohmic Loss of Grooved Polarizer Mirrors in High-Power ECRH Systems

A set of two corrugated polarizer mirrors is typically used in high-power electron cyclotron resonance heating (ECRH) systems to provide the required polarization of the ECRH output beam. The ohmic losses of these mirrors can significantly exceed the losses of plane mirrors depending on the polarization of the incident beam with respect to the orientation of the grooves. Since polarizer mirrors incorporated into miter bends of a corrugated waveguide line are limited in size, active water cooling can become critical in high-power cw systems like the one for ITER. The ohmic loss of polarizer mirrors has been investigated experimentally at high power. A strategy to minimize the losses for given mirror geometries has been found.     

EAST 装置电子回旋共振加热系统波纹圆波导研究*

在EAST装置上正在建设140GHz/4MW/1000s电子回旋共振加热(ECRH)系统,单个回旋管输出的1MW功率通过波纹圆波导传输到天线聚焦镜上,然后经天线反射镜进入等离子体。运用表面阻抗法对波纹圆波导进行了理论分析,针对EAST装置ECRH系统需求的140GHz波纹圆波导进行了设计研究,所设计的波导传输模式为HE11模,具备1MW连续波运行能力且欧姆损耗低于0.02d B/100m,同时分析了HE11模在波导口外辐射模式及其与TEM00模耦合特性。     

Directional couplers in trapped image guide configuration

Dispersion characteristics and wave impedance of trapped coupled image guides are computed by using mode matching techniques. Dispersion curves for trapped coupled image guide are plotted for various dielectric materials and dimensional parameters. The hybrid directional couplers in the above configuration have been theoretically designed by computing the normalization propagation constant.     

Electro magnatic detection of trapped miners

The Bureau of Mines has conducted field studies in coal mines throughout the United States to determine the effectiveness of electromagnetic techniques in locating miners trapped underground following a mine accident. Data from these tests have been used to generate models of expected signal and noise distributions as found above these mines. These distributions have aided in placing the expected performance of a through-the-earth electromagnetic communications technique into a probabilistic framework. Results show that at a 10% false-alarm rate, the expected probability of detecting a miner's signal from a depth of 1000 ft is 54%; at 500 ft it is 95%. These depths exceed the actual depths of 90 and 50%, respectively, of United States coal mines. Sensitivity studies have shown that at a depth of 1000 ft, the probability of detection will improve approximately 2% for each dB of increase in signal-to-noise (SNR) ratio.     

Optical triggering of a trapped plasma

Dense electron-hole pairs trapped in a semiconductor p+-n-n+ structure form a trapped plasma that can conventionally be triggered by applying an overdriven electrical field to initiate impact ionisation. A new optical triggering mode is presented, which uses short light pulses at an electrical field just below the critical level. The optically generated carriers are separated by the applied electrical field and locally raise the electrical field which excites the impact ionisation. The letter describes the physical properties of the triggering process and the results of a one-dimensional computer simulation.     

Saturation velocity of electrons in GaAs

The saturation velocity of electrons in n-GaAs has been deduced from the v/E characteristic over a temperature range 130-400 K. The experimental values are compared with those predicted by a model assuming the velocity to be limited by intervalley scattering in the     

Quantum jumps in a system of few trapped ions

A theory of quantum jumps in a system of few trapped ions is formulated. The V configuration of the energy levels and incoherent pumping are assumed. The master equation is derived in terms of the SU(3) collective operators for the V system. Numerical results for the intensity-intensity correlations for up to five ions are presented. Analytical results for a system of two ions are derived separating out dynamics at two difference time scales and by eliminating adiabatically the fast variables. From the analytical results, the underlying three-state Markov process that can be used to characterize the quantum jumps in the two-ion system is identified. Probability distributions for various off-on time intervals are presented     

利用囚禁离子实现量子博弈

提出了一个利用热囚禁离子来实现两人量子囚徒困境的方案.用双色激光同时照射两个离子,振荡模处于虚激发状态,所以系统对热场不敏感.此外,由于量子博弈中基本的逻辑门可以直接构造,方案相对简单.     

Equivalent electromechanical representation of trapped energy transducers

Trapped energy resonators and transducers have attained a considerable importance in quartz crystal technology both as single-frequency resonators for the control of crystal oscillators and as drivers for the monolithic crystal filter which appears likely to have a wide use as a channel filter for the separation of voice frequency channels for long-distance carrier systems, microwave radio, and submarine cable systems. It is the purpose of this paper to derive the equations for trapped energy resonators of the thickness-shear and thickness-twist types and to calculate the ratios of capacitances for straight crested waves. It turns out that the ratios are lower (coupling higher) than are observed in practice. It appears that this difference is connected with the finite width of the plate which causes the motion at the edge of the plate to be somewhat smaller than the motion in the center of the plate. While no exact solution has been obtained for the finite plate, an approximation is made which is in good agreement with the experiment. The resonator on a plate is a symmetrical device, whereas a transducer for driving a monolithic filter is a dissymmetrical device since it is driving different impedances on its two boundaries. To represent this dissymmetry requires a distributed network representation which is somewhat similar to that found for a plane longitudinal or shear wave except that the propagation constant for a trapped wave replaces that of the plane wave. The representation also requires a transformer whose transformation ratio is a function of the frequency and two negative element terms. By transformations the negative elements can be made to disappear. These together produce an equivalent circuit whose values depend on the ratio of the electrode length to the crystal thickness.