The synchronization of chaotic systems

Homeland security and military defense technology considerations have stimulated intense interest in mobile, high power sources of millimeter-wave (mmw) to terahertz (THz) regime electromagnetic radiation, from 0.1 to 10THz. While vacuum electronic sources are a natural choice for high power, the challenges have yet to be completely met for applications including noninvasive sensing of concealed weapons and dangerous agents, high-data-rate communications, high resolution radar, next generation acceleration drivers, and analysis of fluids and condensed matter. The compact size requirements for many of these high frequency sources require miniscule, microfabricated slow wave circuits. This necessitates electron beams with tiny transverse dimensions and potentially very high current densities for adequate gain. Thus, an emerging family of microfabricated, vacuum electronic devices share many of the same plasma physics challenges that are currently confronting “classic” high power microwave (HPM) generators including long-life bright electron beam sources, intense beam transport, parasitic mode excitation, energetic electron interaction with surfaces, and rf air breakdown at output windows. The contemporary plasma physics and other related issues of compact, high power mmw-to-THz sources are compared and contrasted to those of HPM generation, and future research challenges and opportunities are discussed.

Plasma physics and related challenges of millimeter-wave-to-terahertz and high power microwave generationa)

This article reviews the state-of-the-art in high-power microwave source research. It begins with a discussion of the concepts involved in coherent microwave generation. The main varieties of microwave tubes are classified into three groups, according to the fundamental radiation mechanism involved: Cherenkov, transition, or bremsstrahlung radiation. This is followed by a brief discussion of some of the technical fundamentals of high-power microwave sources, including power supplies and electron guns. Finally, the history and recent developments of both high-peak power and high-average power sources are reviewed in the context of four main areas of application: (1) plasma resonance heating and current drive; (2) rf acceleration of charged particles; (3) radar and communications systems; and (4) high-peak power sources for weapons-effect simulation and exploratory development.

/pdf/review-of-high-power-microwave-source-research-4wfh5blzfg.pdf

Review of high-power microwave source research

Dynamic nuclear polarization for sensitivity enhancement in modern solid-state NMR.

Oscillation quenching mechanisms: Amplitude vs. oscillation death

Contents Introduction Origins of High Power Microwaves High Power Microwave Operating Regimes Future Directions in HPM Further Reading References Designing High Power Microwave Systems The Systems Approach to HPM Looking at Systems Linking Components into a System Systems Issues Scoping an Advanced System Conclusion Problems References High Power Microwave Applications Introduction High Power Microwave Weapons High Power Radar Power Beaming Space Propulsion Plasma Heating Particle Accelerators Problems References Microwave Fundamentals Introduction Basic Concepts in Electromagnetics Waveguides Periodic Slow-Wave Structures Cavities Intense Relativistic Electron Beams Magnetically Insulated Electron Layers Microwave-Generating Interactions Amplifiers and Oscillators, High- and Low-Current Operating Regimes Phase and Frequency Control Summary Problems References Enabling Technologies Introduction Pulsed Power Electron Beams and Layers Microwave Pulse Compression Antennas and Propagation Diagnostics HPM Facilities Problems Further Reading References Ultrawideband Systems UWB Defined UWB Switching Technologies UWB Antenna Technologies UWB Systems Conclusion Problems References Relativistic Magnetrons and MILOS Introduction History Design Principles Operational Features Research and Development Issues Fundamental Limitations MILOs Crossed-Field Amplifiers Summary Problems References BWOs, MWCGs, and O-Type Cerenkov Devices Introduction History Design Principles Operational Features Research and Development Issues Fundamental Limitations Summary Problems References Klystrons and Reltrons Introduction History Design Principles Operational Features Research and Development Issues Fundamental Limitations Summary Problems References Vircators, Gyrotrons and Electron Cyclotron Masers, and Free-Electron Lasers Introduction Vircators Gyrotrons and Electron Cyclotron Masers Free-Electron Lasers Summary Problems References Appendix: High Power Microwave Formulary A.1 Electromagnetism A.2 Waveguides and Cavities A.3 Pulsed Power and Beams Diodes and Beams A.4 Microwave Sources A.5 Propagation and Antennas A.6 Applications Power Beaming Plasma Heating Index

High power microwaves

Observations show that the ubiquitous pulse shortening in high-power microwave (HPM) devices arises from the formation of plasma, electron streaming, high-E-field breakdown, and beam disruption. We review recent experiments in terms of these causes. Linear beam devices exhibit all of these mechanisms; in particular, beam disruption by E/spl times/B drifts in the strong microwave fields and diffusion in turbulent electric fields appear common. In relativistic magnetrons, the dominant effect is resonance destruction by cathode plasma motion, possibly from water contamination of the surface. Wall plasma effects shorten pulses in most sources. We call for the introduction of improved surface conditioning, cathodes which do not produce plasmas, and increased effort on the measurements of the high-field and plasma properties of HPM sources. Because of the broad nature of the phenomena in pulse shortening, we appeal for increased participation of the plasma, intense particle beam, and traditional microwave tube communities in pulse-shortening research.

/pdf/survey-of-pulse-shortening-in-high-power-microwave-sources-4904e3dn43.pdf

Survey of pulse shortening in high-power microwave sources

Phase locking of relativistic magnetrons has been achieved at power levels of \ensuremath{\sim}3 GW at 2.8 GHz, exceeding previous phase-locking power levels by 3 orders of magnitude. Two relativistic magnetrons interact directly through a short waveguide of length $l\ensuremath{\sim}\frac{n\ensuremath{\lambda}}{2}$ to allow locking. Power-density enhancement due to source coherence is directly measured in the radiation field. Phase locking occurs in \ensuremath{\sim}5 ns and is reproducible. Extension to 10-100 GW appears feasible with arrays of oscillators.

Phase Locking of Relativistic Magnetrons

Schemes have been suggested for transferring energy from Earth-to-space, space-to-Earth, and space-to-space using high-power microwave (HPM) beams. All use power beaming. Microwave beams have been studied for propelling spacecraft for launch to orbit, orbit raising, launch from orbit into interplanetary and interstellar space, and deployment of large space structures. The microwave thermal rocket, called the ldquomicrowave thermal thruster,rdquo is a reusable single-stage vehicle that uses an HPM beam to provide power to a heat-exchanger propulsion system, with double the specific impulse of conventional rockets. Orbital missions include orbit raising and space solar power. Microwave-propelled sails are a new class of spacecraft that promises to revolutionize future space probes. Experiments and simulations have verified that sails riding beams can be stable on the beam for conical sail shapes. Beam-driven sail flights have now demonstrated the basic features of the beam-driven propulsion. Beams can also carry angular momentum and communicate it to a sail to help control it in flight. An early mission for microwave space propulsion is dramatically shortening the time needed for sails to escape Earth's orbit. A number of missions for beam-driven sails have been quantified for high-velocity mapping of the outer solar system, Kuiper Belt, the Heliopause, and the penultimate interstellar precursor mission. For large HPM systems at fixed effective isotropic radiated power, minimum capital cost is achieved when the cost is equally divided between antenna gain and radiated power. This is a driver when considering design of power-beaming systems such as interstellar Beacons, which the Search for Extraterrestrial Intelligence is searching for. Much of the technical means for these applications are already in hand. Microwave and millimeter-wave array antennas are already in use for astronomy; sources at high frequencies are being developed for fusion and the military. Development of high-power arrays is needed. A synergistic way to develop a space power-beaming infrastructure is incremental buildup, addressing lower power applications first, and then upgrading.

Space Applications of High-Power Microwaves

Phase locking is considered both for a case in which an oscillator is driven by an external signal without feedback, and for a case in which two coupled oscillators drive each other. A comprehensive sustained oscillator model is used for the driven microwave cavity. The new locking conditions for two coupled oscillators show that phase locking can occur only when the connector contributes the zero or π phase delay. Temporal behavior is solved numerically. Calculations with large priming power agree with the experiments on a high‐power magnetron driven vircator in which there is no feedback to the magnetron. The mutual drive calculations also agree with the experiments on high‐power coupled magnetrons.

James Benford

Papers

High power microwaves

Survey of pulse shortening in high-power microwave sources

Phase Locking of Relativistic Magnetrons

Space Applications of High-Power Microwaves

Phase locking of high-power microwave oscillators