A5031952644- Magnetic confinement fusion research
- Antenna Design and Analysis
- Antenna Design and Optimization
- Laser-Plasma Interactions and Diagnostics
- Laser-induced spectroscopy and plasma
- Gyrotron and Vacuum Electronics Research
- Particle accelerators and beam dynamics
- Ionosphere and magnetosphere dynamics
- Plasma Diagnostics and Applications
- Microwave Engineering and Waveguides
- Advanced Antenna and Metasurface Technologies
- Atomic and Molecular Physics
- Electromagnetic Compatibility and Measurements
- Satellite Communication Systems
- Astro and Planetary Science
- Dust and Plasma Wave Phenomena
- Mass Spectrometry Techniques and Applications
- Physics of Superconductivity and Magnetism
- Cold Atom Physics and Bose-Einstein Condensates
- Radio Astronomy Observations and Technology
- Quantum chaos and dynamical systems
- Fusion materials and technologies
- Gas Dynamics and Kinetic Theory
- Electronic Packaging and Soldering Technologies
- Photorefractive and Nonlinear Optics
RTX (United States)
1985-2019
Raytheon Technologies (Canada)
2005
Motorola (United States)
1997
Plasma Technology (United States)
1980-1985
Massachusetts Institute of Technology
1974-1985
Fusion Academy
1980-1985
Fusion (United States)
1980-1983
United States Department of Energy
1983
Princeton Plasma Physics Laboratory
1975-1978
Princeton University
1975-1978
A quasi-steady-state lower-hybrid current-drive operation is demonstrated in the Alcator $C$ tokamak at densities up to ${\stackrel{-}{n}}_{e}\ensuremath{\simeq}1\ifmmode\times\else\texttimes\fi{}{10}^{14}$ ${\mathrm{cm}}^{\ensuremath{-}3}$. The efficiency measured experimentally over a wide range of and magnetic fields. radial distribution high-energy x rays indicates that current-carrying electrons peak near plasma axis.
Parametric decay processes have been studied using rf probes and CO2 laser scattering during the lower-hybrid wave heating current drive experiments in Alcator C tokamak. The most important process is believed to be nonresonant into ion-cyclotron quasimodes and/or that electron-Landau quasimodes. At lower densities ω0/ωlh(0)>2 [where ω0 frequency of injected pump ωlh(0) evaluated at plasma center], where efficient electron are obtained, parametric absent or very weak. higher...
We report the results of injecting 90 kW microwave power near lower hybrid frequency into Alcator-$A$ tokamak through a two-waveguide array. The observed plasma heating is in disagreement with that expected from linear waveguide-plasma coupling theory. From these and auxiliary rf probe measurements we infer nonlinear formation high-${k}_{\ensuremath{\parallel}}$ wave spectrum at edge.
The results and interpretation of the modest-power (∼90 kW) lower-hybrid-heating experiment on Alcator A are presented. expected from linear waveguide-plasma coupling theory outlined, possible effects parametric instabilities, scattering density fluctuations, imperfect energetic ion confinement addressed. It is found experimentally that good absence RF breakdown achieved with a double waveguide array at available power densities PRF ≤ 4.5 kW.cm·−2, vacuum windows being outside toroidal field...
The wavelengths, amplitudes, frequencies, and spatial distributions of driven lower-hybrid wave fluctuations are studied in the Alcator tokamak with use C${\mathrm{O}}_{2}$-laser scattering. It is found that for incident microwave power densities from 0.4 to 4.5 kW/${\mathrm{cm}}^{2}$ amplitudes nearly independent relative phase electric fields at exciting waveguides. waves not localized resonant cones they have frequency widths 0.5 6 MHz.
The design of a novel phase array panel that provides the L-band satellite to ground links for IRIDIUM global communications system is presented. Key components and aspects this antenna are discussed including beamforming architecture, radiated intermodulation products, patch radiators, T/R module. strategy minimizing DC power consumption over large range multicarrier RF output described. Finally, test results showing compliant operation summarized.
Measurements are presented of the properties lower-hybrid waves excited at edge plasmas in Alcator A tokamak by a two-waveguide array operating microwave powers up to 70 kW. The studied directly plasma measuring small angle scattering CO2 laser radiation. broad N∥ spectrum is observed range 2⩽N∥≲8, with more intensity lower (here, parallel index refraction). distributed throughout minor cross section and do not appear be localized resonance cones. wave amplitude linear net power into plasma....
The behavior of an extraordinary wave normally incident along a decreasing magnetic field gradient in warm collisionless toroidal plasma is considered. Full electromagnetic Vlasov theory used and the density lengths are assumed to be much larger than all wavelengths. In case for which upper hybrid layer accessible, it shown that almost completely converts into backward Bernstein mode at layer. then propagates until absorbed near cyclotron second harmonic generated by this pump calculated,...
The properties of cylindrical electron-emitting plasma probes are reviewed. Poisson's equation is formulated and solved for a emissive probe biased several volts negative potential operating in the space-charge-limited regime. It shown that this regime emitted current at fixed voltage proportional to reciprocal Debye length. theory be good agreement with experimental results. Expected deviations behavior from theory's limitations discussed. Due emission such technique appears useful only...
One challenge in fielding large-scale phased array antennas is calibration of the antenna system, so that RF radiated beams can be accurately formed and steered. Here, we describe two new methods for calibrating large arrays, namely, mobile Fourier gauge (MFG) satellite-based (SatCal) permit rapid arrays on site remove need expensive nearfield facility testing limits size sections aligned. The MFG utilizes a known short line source sequentially moved across using an existing crane; coupling...
We report the results of small-angle ruby-laser Thomson-scattering measurements parametric excitation plasma waves by C${\mathrm{O}}_{2}$-laser radiation at quarter-critical density in a laser-heated gas-target plasma. From supplementary data obtained from interferometry and large-angle scattering we infer that threshold conditions for convective decay are satisfied.
The design of a novel phased array panel that provides the L-band satellite to ground links for IRIDIUM global communications system is presented. Key components and aspects this antenna are discussed, including beamforming architecture, radiated intermodulation products, patch radiators, T/R module. strategy minimizing DC power consumption over large range multicarrier RF output described. Finally, test results showing compliant operation summarized.
The parametric decay of an electromagnetic wave into two electron plasma waves in inhomogeneous is considered. obliquely incident on the density gradient. resulting analysis shows that threshold for absolute instability decreases as angle incidence relative to gradient aproaches 90°. limitations this and its importance laser fusion are discussed.
It is shown that scanning an array of balanced wire or patch type radiators in their <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</tex> -plane can destroy the radiators' dual probe symmetry. This loss symmetry cause radiator's unit cell "scattering matrix" to be nonreciprocal, where this scattering matrix each probes now considered as a separate input port. breaking radiator result scan blindness when fed by reactive power divider balun....
We describe a new method for calibrating large phased arrays, namely the Mobile Fourier Gauge (MFG), that permits rapid calibration of arrays on site, and removes need expensive near field facility testing. This has been demonstrated S-Band array, its accuracy validated.
The presence of a toroidal field ripple greater than 2% in the Alcator A tokamak allows for trapping and rapid ∇B drift loss ions port gap magnet. resulting depletion high-energy is observed by perpendicular charge-exchange measurements may point to significant energetic ion mechanism A. Smaller ripple, larger minor radius higher lead greatly reduced losses C.
The steady state fast ion distribution function and the resulting neutron rate are calculated for conditions of Alcator A lower hybrid heating experiment from quasilinear theory.First, orbit losses ignored is calculated.It found that in this case experimental rates decay times consistent with only a small fraction incident RF power being absorbed plasma center.This centered regime 3.5 < n 1 4.5.A Monte Carlo simulation technique, which incorporates ripple then presented calculates presence...
The objective of the IRIDIUM program is to achieve a global personal satellite communication system based on network 66 communications satellites placed in low earth orbits. A key component each these Main Mission Antenna (MMA), which consists 3 fully active phased array panels, and provides L-band link from ground users. Each panel produces 16 beams, for total 48 beams per satellite, with users communicating through whose beam covers user. quality capacity specifications place unusual...
The possibility of heating collisionless toroidal plasmas to high temperatures by means linear wave absorption above the lower hybrid frequency is discussed. This mainly due electron Landau damping and ion neglected. Two methods are considered, propagating a across plasma column exciting modes. WKB solutions first method show that incident must be within narrow range kz for its energy uniformly deposited into plasma. Toroidal mode indicate this band may significantly widened waves which...
ABSTRACT An electromagnetic analysis technique for probe–fed patch radiator phased arrays is presented that accurately models their driving point impedances and radiated electric fields. The use of this methodology to both predict the behavior design radiators discussed. Salient features relevant synthesis are discussed, including asymmetries due multiple probe feeds realization matching networks wideband operation. Key effects performance, such as feed–network related resonances surface...
A design methodology that has been successfully used to obtain probe-fed patch radiator phased-array bandwidths of approximately 15% is reported. This based on the use an accurate numerical code synthesize architecture. second step mathematically couples this with double-tuned matching networks, which have previously in patches. In procedure all probes are treated as independent input ports patch, and radiator's scattering matrix explicitly calculated. The resulting radiator/matching network...
In order to achieve the 48 cell coverage in Iridium program, as well desired high-quality data links between users and satellite, a high-efficiency, linear, lightweight, space-qualified phased array panel must be designed that can simultaneously transmit or receive 16 beams. The aperture illuminations of Main Mission Antenna (MMA) panels have been synthesized so consistent with Butler-matrix-type beamformer generates required shaped beams minimal losses. unified design is considered, RF T/R...