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Significant advances in microwave and millimeter wave technology over the past decade have enabled the development of a new generation of imaging diagnostics for current and envisioned magnetic fusion devices. Prominent among these are microwave electron cyclotron emission imaging, microwave phase imaging interferometers, imaging microwave scattering, and microwave imaging reflectometer systems for imaging Te and ne fluctuations (both turbulent and coherent) and profiles (including transport barriers) on toroidal devices such as tokamaks, spherical tori, and stellarators. The diagnostic technology is reviewed, and typical diagnostic systems are analyzed. Representative experimental results obtained with these novel diagnostic systems are also presented.

Resonant frequencies and unloaded Q's of hybrid modes on cylindrical dielectric resonators in conducting enclosures are studied. The formulation uses the mode matching technique, and includes axially symmetric (TE0m and/or TM0m), as well as axially non-symmetric hybrid (HEnm,) modes which could exist in dielectric loaded waveguides. The structures analyzed can simulate resonators on ground plane backed or suspended substrates. Losses in the conducting walls, substrates, and the dielectric material, and stored energy in the general resonator are obtained. Mode amplitudes determined from the solution of the boundary value problem by mode matching are used to rigorously compute the unloaded Q's of the resonators. Numerical results in the millimeter wave range and in C-band are presented. These results include unloaded Q's and mode charts of dielectric resonators on ground plane backed and suspended substrate structures. From these results, methods for improving the unloaded Q's and mode's separation are expl...

Summary form only given. An exciting tool for the study and visualization of plasma turbulence is presently under development for the TEXTOR-94 tokamak. This system combines a high resolution electron cyclotron emission imaging (ECEI) diagnostic with an innovative microwave imaging reflectometer (MIR) diagnostic for the simultaneous localized measurement of electron temperature T. and electron density n/sub e/ fluctuations in the tokamak core. The ECEI diagnostic images second harmonic cyclotron radiation from the optically thick plasma onto a 1-D array, thereby forming an image of the T/sub e/ profile and fluctuations associated with the emission layer. The MIR diagnostic images radiation reflected from the plasma cutoff layer onto a similar 1-D array, thus forming an image of n/sub e/ fluctuations at the reflecting layer. Both diagnostics are capable of forming 2-D images of plasma turbulence by varying the frequency of the probing (for MIR) or received (for ECEI) signals. Adjustment of the reflectometer probing frequency permits the reflecting layer to be positioned coincident with the ECEI emission layer, thereby simultaneously sampling both T/sub e/ and n/sub e/ fluctuations over an extended surface of the TEXTOR-94 plasma. Such data will permit the visualization of complicated 2-D and/or 3-D structures which is essential for definitive comparisons to be made with the predictions of gyrokinetic computer simulations. In addition, the system will also be employed in the study of a number of MM phenomena such as plasma filament formation, magnetic islands and internal transport barriers. An overview of the simultaneous imaging diagnostic concept will be presented along with technical details and characterization measurements of the TEXTOR-94 diagnostic. The system is presently under fabrication, and will begin operation in August, 2002 when TEXTOR-94 resumes operation after the installation of a dynamic ergodic divertor.

It is shown that with high-quality, large-area YBCO films and simple, styrofoam mounts, unloaded X-band Q values of over 250 thousand are attainable for TE/sub 01/ mode operation of a sapphire dielectric resonator (DR) operated at 77 K and employing high-temperature superconducting (HTS) films installed in the DR enclosure covers. Rigorous analysis for the determination of resonator frequency, modes, and unloaded Q have been carried out using mode matching techniques. The results of both analysis and prototype device evaluation experiments are compared for resonators fabricated using enclosures consisting of conventional metal sidewalls and covers using HTS films as a function of cover conductivity. >

Significant advances in microwave and millimeter wave technology over the past decade have enabled the development of a new generation of imaging diagnostics for current and envisioned magnetic fusion devices. Prominent among these are revolutionary microwave electron cyclotron emission imaging (ECEI), microwave phase imaging interferometers, imaging microwave scattering and microwave imaging reflectometer (MIR) systems for imaging electron temperature and electron density fluctuations (both turbulent and coherent) and profiles (including transport barriers) on toroidal devices such as tokamaks, spherical tori, and stellarators. The diagnostic technology is reviewed, and typical diagnostic systems are analyzed. Representative experimental results obtained with these novel diagnostic systems are also presented.

The anomalous transport in magnetized plasmas remains to be an outstanding issue, which in large part due to the difficulty in diagnosing the small amplitude fluctuations in the high temperature plasma core1. Recent progress in fusion studies has motivated the development of advanced microwave imaging diagnostics, both to visualize the elegant three-dimensional (3-D) structures of plasma turbulence revealed by extensive computer simulations2 and to perform high spatial and temporal resolution measurement of turbulent fluctuations in the plasma core, such as Te fluctuation measurements by ECE imaging. A third motivation is the recent discovery of the problem with conventional reflectometry and the need for imaging reflectometry as an essential tool for density fluctuation measurements3. The fourth is the need to measure fine scale structures in profiles of transport significance, such as filamentation and internal transport barriers4. The focus and emphasis of this paper will therefore primarily be on the dramatic breakthroughs occurring in electron cyclotron emission imaging (ECEI) and microwave imaging reflectometry (MIR), which will ultimately permit the imaging and visualization of complicated 2-D and 3-D structures of both electron temperature and density.

An n-ZnO/p-ZnO : Sb homojunction light emitting diode was fabricated on c-plane sapphire by metal–organic chemical vapour deposition (MOCVD). The p-type ZnO layer with a hole concentration of 1.27 × 1017 cm−3 was fabricated using trimethylantimony (TMSb) as the Sb doping source. The current–voltage characteristics of the device exhibited a desirable rectifying behaviour with a turn-on voltage of 3.3 V. Distinct electroluminescence with ultraviolet and visible emissions was detected from this device under forward bias at room temperature. Moreover, metal–organic source TMSb is an effective and controllable dopant in the MOCVD technique, which is suitable for further industrialized production.

ZnO homojunction light-emitting diode with n-ZnO∕p-ZnO:As∕GaAs structure is produced by metal organic chemical vapor deposition. The p-type ZnO:As film is obtained out of thermal diffusion of arsenic from GaAs substrate with subsequent thermal annealing at 550°C. The n-type layer is composed of unintentionally doped ZnO film. Desirable rectifying behavior is observed from the current-voltage curve of the ZnO p-n homojunction. Furthermore, two distinct electroluminescence bands centered at 3.2 and 2.5eV are obtained from the junction under forward bias at room temperature.