Physics and Astronomy › Atomic and Molecular Physics, and Optics

Gyrotron and Vacuum Electronics Research

Works Count: 63550

Wikipedia

Description

This cluster of papers focuses on the development, theory, and applications of high-power vacuum electronic sources, particularly in the terahertz frequency range. It covers topics such as gyrotrons, plasma physics, microwave generation, electron cyclotron masers, traveling-wave tubes, dynamic nuclear polarization, space-charge-limited flow, and high-power microwave devices.

Keywords

Vacuum Electronics; High Power Terahertz Sources; Gyrotrons; Plasma Physics; Microwave Generation; Electron Cyclotron Masers; Traveling-Wave Tubes; Dynamic Nuclear Polarization; Space-Charge-Limited Flow; High-Power Microwave Devices

Modern Microwave and Millimeter-Wave Power Electronics

2005-01-01

R.J. Barker , Neville C. Luhmann , John H. Booske +1 more

Dedication. Foreword by Baruch Levush. Preface. Acknowledgements. List of Contributors. List of Acronyms and Abbreviations. Chapter 1. Introduction and Overview. Chapter 2. Historical Highlights. Chapter 3. Klystrons. Chapter 4. Traveling … Dedication. Foreword by Baruch Levush. Preface. Acknowledgements. List of Contributors. List of Acronyms and Abbreviations. Chapter 1. Introduction and Overview. Chapter 2. Historical Highlights. Chapter 3. Klystrons. Chapter 4. Traveling Waves Tubes (TWTs). Chapter 5. Gyro-Amplifiers. Chapter 6. Crossed-Field Devices. Chapter 7. Microfabricated MVEDs. Chapter 8. Advanced Electron Beam Sources. Chapter 9. How to Achieve Linear Amplification. Chapter 10. Computational Modeling. Chapter 11. Next-Generation Microwave Structures and Circuits. Chapter 12. Advanced Materials Technologies for MVEDs. Chapter 13. High Power Microwave (HPM) Sources. Chapter 14. Affordable Manufacturing. Chapter 15. Emerging Applications and Future Possibilities. Index. About the Editors. Appendices.

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

2008-02-27

John H. Booske

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 … 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.

Water vapor microwave continuum absorption: A comparison of measurements and models

1998-07-01

P. W. Rosenkranz

Measurements, made in different laboratories, of absorption by water vapor in microwave windows are compared with models for the water vapor continuum. A reanalysis of some of these measurements leads … Measurements, made in different laboratories, of absorption by water vapor in microwave windows are compared with models for the water vapor continuum. A reanalysis of some of these measurements leads to the conclusion that the laboratory data are best represented by a combination of Liebe's [1987] millimeter‐wave propagation model (MPM) for the foreign‐broadened component of the water continuum and the 1993 version of MPM for the self‐broadened component. This combined model is validated by comparison with measurements of atmospheric microwave emission.

Observation of Terahertz Emission from a Laser-Plasma Accelerated Electron Bunch Crossing a Plasma-Vacuum Boundary

2003-08-14

Wim Leemans , C. G. R. Geddes , J. Fauré +7 more

Coherent radiation in the 0.3-3 THz range has been generated from femtosecond electron bunches at a plasma-vacuum boundary via transition radiation. The bunches produced by a laser-plasma accelerator contained 1.5 … Coherent radiation in the 0.3-3 THz range has been generated from femtosecond electron bunches at a plasma-vacuum boundary via transition radiation. The bunches produced by a laser-plasma accelerator contained 1.5 nC of charge. The THz energy per pulse within a limited 30 mrad collection angle was 3-5 nJ and scaled quadratically with bunch charge, consistent with coherent emission. Modeling indicates that this broadband source produces about 0.3 microJ per pulse within a 100 mrad angle, and that increasing the transverse plasma size and electron beam energy could provide more than 100 microJ/pulse.

Irradiation synchronized with respiration gate

1989-10-01

Kiyoshi Ohara , Toshiyuki Okumura , Masayoshi Akisada +4 more

Generation of 1.5-kW, 1-THz Coherent Radiation from a Gyrotron with a Pulsed Magnetic Field

2008-01-11

M. Yu. Glyavin , А. Г. Лучинин , G. Yu. Golubiatnikov

To cover a so-called terahertz gap in available sources of coherent electromagnetic radiation, the gyrotron with a pulsed solenoid producing up to a 40 T magnetic field has been designed, … To cover a so-called terahertz gap in available sources of coherent electromagnetic radiation, the gyrotron with a pulsed solenoid producing up to a 40 T magnetic field has been designed, manufactured, and tested. At a 38.5 T magnetic field, the gyrotron generated coherent radiation at 1.022 THz frequency in 50 musec pulses. The microwave power and energy per pulse were about 1.5 kW and 75 mJ, respectively. Details of the gyrotron design, manufacturing, operation and measurements of output radiation are given.

Magnetron sputtering: basic physics and application to cylindrical magnetrons

1978-03-01

John A. Thornton

Magnetron sputtering sources can be defined as diode devices in which magnetic fields are used in concert with the cathode surface to form electron traps which are so configured that … Magnetron sputtering sources can be defined as diode devices in which magnetic fields are used in concert with the cathode surface to form electron traps which are so configured that the E×B electron-drift currents close on themselves. Coaxial cylindrical magnetron sputtering sources in which post or hollow cathodes are operated in axial magnetic fields have been reported for a number of years. However, their performance is limited by end losses. A remarkable performance is achieved when the end losses are eliminated by proper shaping of the magnetic field or by using suitably placed electron-reflecting surfaces. High currents and sputtering rates can be obtained, nearly independent of voltage, even at low pressures. This characterizes what has been defined as the magnetron mode of operation. This paper reviews the basic principles that underly the operation of dc sputtering sources in the magnetron mode with particular emphasis on cylindrical magnetrons. The important attributes of these devices as sputtering sources are also reviewed.

Filling the THz gap—high power sources and applications

2005-12-05

Gwyn Williams

Electromagnetic waves centred at a frequency of 1 THz lie between photonics on the one hand and electronics on the other, and are very hard to generate and detect. However, … Electromagnetic waves centred at a frequency of 1 THz lie between photonics on the one hand and electronics on the other, and are very hard to generate and detect. However, since the THz part of the spectrum is energetically equivalent to many important physical, chemical and biological processes including superconducting gaps and protein dynamical processes, it is of great interest to facilitate experimental research in this region. This has stimulated major steps in the past decade for filling this gap in the usable spectrum. In this review paper we describe the evolution of a new generation of sources that boost the average power available in the THz region by more than a million-fold, making this region routinely accessible for the first time. This is achieved using two enhancement factors, namely relativistic electrons and super-radiance. We will also point to the scientific potential for discovery that is now enabled in this region.

Concept of nonintegrable phase factors and global formulation of gauge fields

1975-12-15

Tai Tsun Wu , Chen Ning Yang

Through an examination of the Bohm-Aharonov experiment an intrinsic and complete description of electromagnetism in a space-time region is formulated in terms of a nonintegrable phase factor. This concept, in … Through an examination of the Bohm-Aharonov experiment an intrinsic and complete description of electromagnetism in a space-time region is formulated in terms of a nonintegrable phase factor. This concept, in its global ramifications, is studied through an examination of Dirac's magnetic monopole field. Generalizations to non-Abelian groups are carried out, and result in identification with the mathematical concept of connections on principal fiber bundles.

Large-Orbit Gyrotron Operation in the Terahertz Frequency Range

2009-06-18

V. L. Bratman , Yu. K. Kalynov , В. Н. Мануилов

Coherent terahertz high-harmonic radiation has been obtained in a gyrotron with an axis-encircling electron beam. An electron-optical system with a cusp gun and a following drift section of adiabatic magnetic … Coherent terahertz high-harmonic radiation has been obtained in a gyrotron with an axis-encircling electron beam. An electron-optical system with a cusp gun and a following drift section of adiabatic magnetic compression with an area factor of 3000 provides the formation of an $80\mathrm{\text{\ensuremath{-}}}\mathrm{keV}/0.7\mathrm{\text{\ensuremath{-}}}\mathrm{A}$ beam of gyrating electrons in a wide range of voltages and magnetic fields. Stable single-mode generation with a power of 0.3--1.8 kW in microsecond pulses is detected at four frequencies in the range 0.55--1.00 THz at resonant magnetic fields 10.5--14 T.

Coupling of Modes of Propagation

1954-02-01

John R. Pierce

When two lossless modes of propagation are coupled, waves which increase or decrease with distance may arise when the power flow of the two modes is in opposite directions or … When two lossless modes of propagation are coupled, waves which increase or decrease with distance may arise when the power flow of the two modes is in opposite directions or when power is generated in the coupling device. This behavior is characteristic of wave filters, traveling-wave tubes, double-stream amplifiers, and space-charge-wave amplifiers. Such behavior is analyzed assuming linearity and conservation of energy only.

<i>High-Energy Electromagnetic Processes in Condensed Media</i>

1973-03-01

M. L. Ter-Mikaelian , L. S. Osborne

A Proposed High-Frequency, Negative-Resistance Diode

1958-03-01

W. T. Read

This paper describes and analyzes a proposed semiconductor diode designed to operate as an oscillator when mounted in a suitable microwave cavity. The frequency would be in the range extending … This paper describes and analyzes a proposed semiconductor diode designed to operate as an oscillator when mounted in a suitable microwave cavity. The frequency would be in the range extending from 1 to 50 kmc. The negative Q may be as low as 10 and the efficiency as high as 30 per cent. The diode is biased in reverse so as to establish a depletion, or space-charge, layer of fixed width in a relatively high resistance region, bounded by very low resistance end regions. The electric field has a maximum at one edge of the space-charge region, where hole-electron pairs are generated by internal secondary emission, or avalanche. The holes (or electrons) travel across the space-charge layer with constant velocity, thus producing a current through the diode. Because of the build-up time of the avalanche, and the transit time of the holes across the depletion layer, the alternating current is delayed by approximately one-half cycle relative to the ac voltage. Thus, power is delivered to the ac signal. When the diode is mounted in an inductive microwave cavity tuned to the capacity of the diode, an oscillation will build up. It appears possible to obtain over 20 watts of ac power in continuous operation at 5 kmc.

Microwave Discharge Cavities Operating at 2450 MHz

1965-03-01

F. C. Fehsenfeld , K. M. Evenson , H. P. Broida

Five simple microwave cavities for producing discharges in gases were tested in He and H2 at pressures from 1 μ to 1 atm. Three of the cavities are commonly used, … Five simple microwave cavities for producing discharges in gases were tested in He and H2 at pressures from 1 μ to 1 atm. Three of the cavities are commonly used, and two have been recently designed. One of the newly designed cavities offered a considerable improvement over early models with respect to compactness, ease of attachment to the system, and efficiency.

Split-ring resonator for use in magnetic resonance from 200–2000 MHz

1981-02-01

W. N. Hardy , Lorne Whitehead

A novel high Q resonator is described that is suitable for magnetic resonance in the frequency region 200–2000 MHz, where ordinary cavities are generally too bulky and solenoidal coils impractical. A novel high Q resonator is described that is suitable for magnetic resonance in the frequency region 200–2000 MHz, where ordinary cavities are generally too bulky and solenoidal coils impractical.

Velocity matching by pulse front tilting for large area THz-pulse generation

2002-10-21

János Hebling , Gábor Almási , I. Z. Kozma +1 more

We propose a generally applicable velocity matching method for THz-pulse generation by optical rectification in the range below the phonon frequency of the nonlinear material. Velocity matching is based on … We propose a generally applicable velocity matching method for THz-pulse generation by optical rectification in the range below the phonon frequency of the nonlinear material. Velocity matching is based on pulse front tilting of the ultrashort excitation pulse and is able to produce a large area THz beam. Tuning of the THz radiation by changing the tilt angle is experimentally demonstrated for a narrow line in the range between 0.8- 0.97 times the phonon frequency. According to model calculations broadband THz radiation can be generated at lower frequencies. Advantages of the new velocity matching technique in comparison to the electro-optic Cherenkov effect and non-collinear beam mixing are discussed.

The electron cyclotron maser

2004-05-04

K. R. Chu

The electron cyclotron maser (ECM) is based on a stimulated cyclotron emission process involving energetic electrons in gyrational motion. It constitutes a cornerstone of relativistic electronics, a discipline that has … The electron cyclotron maser (ECM) is based on a stimulated cyclotron emission process involving energetic electrons in gyrational motion. It constitutes a cornerstone of relativistic electronics, a discipline that has emerged from our understanding and utilization of relativistic effects for the generation of coherent radiation from free electrons. Over a span of four decades, the ECM has undergone a remarkably successful evolution from basic research to device implementation while continuously being enriched by new physical insights. By delivering unprecedented power levels, ECM-based devices have occupied a unique position in the millimeter and submillimeter regions of the electromagnetic spectrum, and find use in numerous applications such as fusion plasma heating, advanced radars, industrial processing, materials characterization, particle acceleration, and tracking of space objects. This article presents a comprehensive review of the fundamental principles of the ECM and their embodiment in practical devices.

Traveling-Wave Tubes

1950-04-01

John R. Pierce

A SIDE FROM HELICES, the circuits most commonly used in traveling-wave tubes are iterated or filter-type circuits, composed of linear arrays of coupled resonant slots or cavities. A SIDE FROM HELICES, the circuits most commonly used in traveling-wave tubes are iterated or filter-type circuits, composed of linear arrays of coupled resonant slots or cavities.

The Theory of Anomalous Diffraction Gratings and of Quasi-Stationary Waves on Metallic Surfaces (Sommerfeld’s Waves)

1941-03-01

U. Fano

The theory of Wood's anomalous diffraction gratings, which was developed some years ago, has been reexamined in order to visualize its physical meaning. Each wave diffracted by a grating is … The theory of Wood's anomalous diffraction gratings, which was developed some years ago, has been reexamined in order to visualize its physical meaning. Each wave diffracted by a grating is identified through the component of its "wave vector" tangential to the grating. Surface waves similar to those found in total internal reflection are included (§2). The amplitudes of these waves can be calculated by successive approximations (§3). One feature of the anomalies is connected with the infinite dispersion of spectra at grazing emergence (§4). Emphasis is put on the existence of polarized quasi-stationary waves which represent an energy current rolling along the surface of a metal (§5). These waves can be strongly excited on the surface of metallic gratings under critical conditions depending also on the profile of the grooves; secondary interference phenomena arise then in the observed spectra (§6). The connection of the quasi-stationary surface waves with the wireless ground waves is discussed (§7). A general formulation is introduced to discuss the significance of the approximation used (Appendix).

Currents Limited by Space Charge between Concentric Spheres

1924-07-01

Irving Langmuir , Katharine B. Blodgett

Limiting current between concentric spheres; calculation of the function $\ensuremath{\alpha}=f(\frac{r}{{r}_{0}})$ in the space charge equation $i=(\frac{4\sqrt{2}}{9})\frac{\sqrt{(\frac{e}{m})}{V}^{\frac{3}{2}}}{{\ensuremath{\alpha}}^{2}}$.---The coefficients of the first six terms of a series for $\ensuremath{\alpha}$ were determined, and … Limiting current between concentric spheres; calculation of the function $\ensuremath{\alpha}=f(\frac{r}{{r}_{0}})$ in the space charge equation $i=(\frac{4\sqrt{2}}{9})\frac{\sqrt{(\frac{e}{m})}{V}^{\frac{3}{2}}}{{\ensuremath{\alpha}}^{2}}$.---The coefficients of the first six terms of a series for $\ensuremath{\alpha}$ were determined, and ${\ensuremath{\alpha}}^{2}$ calculated from this series. The results were checked by an integration method which was also used to calculate values in the region where the series failed. For an emitter of radius ${r}_{0}$ inside a collector of radius $r$, values of ${\ensuremath{\alpha}}^{2}$ when $log(\frac{r}{{r}_{0}})>6.4$ are given by the equation $\frac{1}{2}{\ensuremath{\alpha}}^{2}=0.112 log (\frac{logr}{{r}_{0}})+\frac{1}{3}log (\frac{r}{{r}_{0}})+0.152.$ Where the collector is the inside sphere, values of ${\ensuremath{\alpha}}^{2}$ for $\frac{{r}_{0}}{r}>9$ are given by the equation ${(\frac{1}{2}{\ensuremath{\alpha}}^{2})}^{\frac{2}{3}}=1.11 (\frac{{r}_{0}}{r})\ensuremath{-}1.64$. It is shown that when the collector is the inside sphere the potential distribution near the collector is unaltered if the emitter is replaced by a non-emitting sphere with a diameter.677 times the original diameter.Limiting current between coaxial cylinders and between concentric spheres.---Equations are derived for the current in terms of the radius of curvature of the emitter. It is shown that at a surface in space four-fifths of the distance from the emitter to the collector the current density is independent of the radius of curvature when $\frac{r}{{r}_{0}} or \frac{{r}_{0}}{r}<2$; and in the case of coaxial cylinders with the emitter inside this holds true even when $\frac{r}{{r}_{0}}=20$.

High-power terahertz radiation from relativistic electrons

2002-11-01

G. L. Carr , Michael C. Martin , Wayne R. McKinney +3 more

Relativistic gyrotrons and cyclotron autoresonance masers

1981-10-01

V. L. Bratman , N. S. Ginzburg , Gregory S. Nusinovich +2 more

Abstract As follows from theory, supported by experiment, if the electron energy grows to ∼ 1 McV the gyroton preserves its capability to produce single-mode radiation in the millimetere wave … Abstract As follows from theory, supported by experiment, if the electron energy grows to ∼ 1 McV the gyroton preserves its capability to produce single-mode radiation in the millimetere wave range with rather high efficiency. If the electron energy is ultra-relativistic (≳ 1 McV), preference must be given to the eyelotron auto-resonance maser, which is, in principle, the most effective type of free electron laser (‘ doppertron’) at milimetere and submillimetre wavelengths.

Relaxation of Optically Pumped Rb Atoms on Paraffin-Coated Walls

1966-07-08

Marie-Anne Bouchiat , J. Brossel

Relaxation of optically pumped Rb atoms on paraffin-coated walls has been studied using Franzen's sequence (relaxation in the dark) for observables $〈{S}_{z}〉$ (mean electronic longitudinal polarization), and <S\ifmmode\cdot\else\textperiodcentered\fi{}I> (population difference … Relaxation of optically pumped Rb atoms on paraffin-coated walls has been studied using Franzen's sequence (relaxation in the dark) for observables $〈{S}_{z}〉$ (mean electronic longitudinal polarization), and <S\ifmmode\cdot\else\textperiodcentered\fi{}I> (population difference between the two hfs levels). The physical meaning of optical signals under different conditions is analyzed in some detail, and it is pointed out that different observables relax differently. In the interpretation of our results, extensive use has been made of the theoretical analysis of the relaxation of a spin S (coupled to a spin I in the Rb atom) caused by a weak interaction of the type $_{\ensuremath{\gamma}s}H(t)\ifmmode\cdot\else\textperiodcentered\fi{}\mathbf{S}$, $H(t)$ being a random magnetic field acting on S during the dwell time of a Rb atom on the wall. Experimental results are in excellent agreement with this analysis, if one assumes the existence of two uncorrelated interactions of the above type. The first is the dipole-dipole interaction between S and the nuclear spins K of the protons (or deuterons) of the coating. This interaction has a long correlation time ${\ensuremath{\tau}}_{c1}\ensuremath{\approx}4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$ sec and dominates the relaxation of $〈{S}_{z}〉$ in low fields. The second interaction which is independent of spins K, has a short correlation time ${\ensuremath{\tau}}_{c2}\ensuremath{\approx}{10}^{\ensuremath{-}12}$ sec, and dominates the relaxation of <S\ifmmode\cdot\else\textperiodcentered\fi{}I> in low fields, and of $〈{S}_{z}〉$ in large fields. The values of these correlation times and of the strengths of the two interactions have been measured, first in low fields by combining results on $〈{S}_{z}〉$ and <S\ifmmode\cdot\else\textperiodcentered\fi{}I> for the two Rb isotopes and for two types of coatings [${(\mathrm{C}{\mathrm{H}}_{2})}_{n}$ and ${(\mathrm{C}{\mathrm{D}}_{2})}_{n}$], and second, by studying the variations of the "pseudo" relaxation time ${T}_{1}$ of $〈{S}_{z}〉$ for magnetic-field values up to 5000 G. We arrive at a detailed picture of physical adsorption of Rb on paraffin-coated walls, and find 0.1 eV for the adsorption energy. These results are compatible with those obtained for the relaxation of oriented Rb atoms in collisions with buffer-gas molecules.

Review of high-power microwave source research

1997-11-01

Steven H. Gold , Gregory S. Nusinovich

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 … 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.

The Interaction of Electron and Positive Ion Space Charges in Cathode Sheaths

1929-06-01

Irving Langmuir

Effect of positive ions generated at a plane anode upon the space charge limitation of electron currents from a parallel cathode.---Mathematical analysis shows that single ions emitted with negligible velocity … Effect of positive ions generated at a plane anode upon the space charge limitation of electron currents from a parallel cathode.---Mathematical analysis shows that single ions emitted with negligible velocity permit 0.378 ${(\frac{{m}_{p}}{{m}_{e}})}^{\frac{1}{2}}$ additional electrons to pass; but with an unlimited supply of ions the electron current approaches a limiting value 1.860 times that which flows when no ions are present, and the electron current is then ${(\frac{{m}_{p}}{{m}_{e}})}^{\frac{1}{2}}$ times the ion current, both currents thus being limited by space charge and the electric field being symmetrically distributed between the electrodes. Single ions introduced into a pure electron discharge at a point $\frac{4}{9}\mathrm{ths}$ of the distance from cathode to anode produce a maximum effect, 0.582 ${(\frac{{m}_{p}}{{m}_{e}})}^{\frac{1}{2}}$, in increasing the electron current. These conditions apply to a cathode emitting a surplus of electrons surrounded by ionized gas. The cathode sheath is then a double layer with an inner negative space charge and an equal outer positive charge, the field being zero at the cathode and at the sheath edge. The electron current is thus limited to ${(\frac{{m}_{p}}{{m}_{e}})}^{\frac{1}{2}}$ times the rate at which ions reach the sheath edge. If ions are generated without initial velocities uniformly throughout the space between two plane electrodes, a parabolic potential distribution results. If the total ion generation exceeds 2.86 times the ion current that could flow from the more positive to the more negative electrode, a potential maximum develops in the space. Electrons produced by ionization are trapped within this region and their accumulation modifies the potential distribution yielding a region (named plasma) in which only weak fields exist and where the space charge is nearly zero. The potential distribution in the plasma, given by the Boltzmann equation from the electron temperature and the electron concentrations, determines the motions of the ions and thus fixes the rate at which the ions arrive at the cathode sheath. The anode sheath is usually also a positive ion sheath, but with anodes of small size a detached double-sheath may exist at the boundary of the anode glow. In discharges from hot cathodes in gases where the current is limited by resistance in series with the anode, the electron current is space-charge-limited, being fixed by the rate of arrival of ions at the cathode sheath. Thus the cathode drop is fixed by the necessity of supplying the requisite number of ions to the cathode. The effect of the initial velocities of the ions and electrons that enter a double-sheath from the gas is to decrease the electron current by an amount that varies with the voltage drop in the sheath. A nearly complete theory of this effect is worked out for plane electrodes. A detailed study is made of the potential distribution in the plasma and near the sheath edge for a particular case and the conclusion is drawn that the velocities of the ions that enter the sheath can be calculated from the electron temperature if the geometry of the source of ionization is given.Experiments with double sheaths.---With large cathodes coated with barium oxide in low pressure mercury vapor, simultaneous measurements showed that the electron current density was independent of the cathode temperature and was from 140 to 200 times the ion current density, this ratio being independent of the intensity of ionization and of the gas pressure but varying slowly with the voltage drop in the cathode sheath, in good accord with the theory. The observed ratio, however, was about 40 percent of that calculated, this discrepancy being probably due to nonuniformity in the cathode coating. Similar results were obtained with double sheaths on wire type cathodes, the ratio of the electron current to the ion current through the sheath ranging from 450:1 at high current densities to 2000:1 and more at very low currents, this variation being in agreement with the approximate theory developed for cylindrical sheaths. In these experiments two cathodes were used; one at rather large negative voltage to produce any desired intensity of ionization, while from the volt-ampere characteristics of the other cathode the space-charge-limited electron currents were measured. The ion currents were measured either by cooling the test cathode so that it emitted no electrons, or by the use of an auxiliary ion collector.

Electron Spin Resonance Absorption in Metals. II. Theory of Electron Diffusion and the Skin Effect

1955-04-15

Freeman J. Dyson

The theory of paramagnetic resonance absorption by the conduction electrons in a metal is worked out, taking into account the diffusion of the electrons in and out of the thin … The theory of paramagnetic resonance absorption by the conduction electrons in a metal is worked out, taking into account the diffusion of the electrons in and out of the thin skin into which the radio-frequency field penetrates. Calculations are carried through in detail for the case of a flat metal plate. It is found that the diffusion has no marked effect on the width of the resonance absorption line, but has a radical effect on the shape of the line. In particular, for a piece of metal thick compared to the skin depth and with a relaxation time long compared to the diffusion time, the line is antisymmetrical about its center and has an unusual characteristic shape.

On the calculation of the energy of a Bloch wave in a metal

1947-08-01

J. Korringa

Frequency-Independent and Frequency-Dependent Nonlinear Models of TWT Amplifiers

1981-11-01

A.A.M. Saleh

Simple two-parameter formulas are presented for the functions involved in the amplitude-phase and the quadrature nonlinear models of a TWT amplifier, and are shown to fit measured data very well. … Simple two-parameter formulas are presented for the functions involved in the amplitude-phase and the quadrature nonlinear models of a TWT amplifier, and are shown to fit measured data very well. Also, a closed-form expression is derived for the output signal of a TWT amplifier excited by two phase-modulated carriers, and an expression containing a single integral is given when more than two such earriers are involved. Finally, a frequencydependent quadrature model is proposed whose parameters are obtainable from single-tone measurements.

Passive high-power microwave components

2002-06-01

M. Thumm , W. Kasparek

This review discusses the present state-of-the-art of passive high-power microwave components for applications in microwave systems for RF plasma generation and heating, plasma diagnostics, plasma and microwave materials processing, spectroscopy, … This review discusses the present state-of-the-art of passive high-power microwave components for applications in microwave systems for RF plasma generation and heating, plasma diagnostics, plasma and microwave materials processing, spectroscopy, communication, radar ranging and imaging, and for drivers of next generation high-field-gradient electron-positron linear colliders. The paper reports on high-power components for overmoded high-power transmission systems such as smooth-wall waveguides, HE/sub 11/ hybrid mode waveguides and quasi-optical TEM/sub 00/ beam waveguides. These include various types of mode converters, polarizers, cross-section tapers, bends, mode selective filters, pulse compressors, DC-breaks, directional couplers, beam combiners and dividers, vacuum windows, and instruments for mode analysis. Problems of ohmic attenuation and unwanted conversion to parasitic modes are discussed in detail and rules for alignment requirements are given. In the case of waveguide transmission, this review mainly concentrates on circular waveguide components but also deals with rectangular waveguide.

Black-hole normal modes: A WKB approach. I. Foundations and application of a higher-order WKB analysis of potential-barrier scattering

1987-06-15

Sai Iyer , Clifford M. Will

We present a semianalytic technique for determining the complex normal-mode frequencies of black holes. The method makes use of the WKB approximation, carried to third order beyond the eikonal approximation. … We present a semianalytic technique for determining the complex normal-mode frequencies of black holes. The method makes use of the WKB approximation, carried to third order beyond the eikonal approximation. Mathematically, the problem is similar to studying one-dimensional quantum-mechanical scattering near the peak of a potential barrier, and determining the scattering resonances. Under such conditions, a modification of the usual WKB approach must be used. We obtain the connection formulas that relate the amplitudes of incident, reflected, and transmitted waves, to the third WKB order. By imposing the normal-mode (resonance) boundary condition of a zero incident amplitude with nonzero transmitted and reflected amplitudes, we find a simple formula that determines the real and imaginary parts of the normal-mode frequency of perturbation (or of the quantum-mechanical energy of the resonance) in terms of the derivatives (up to and including sixth order) of the barrier function evaluated at the peak, and in terms of the quantity (n+(1/2)), where n is an integer and labels the fundamental mode (resonance), first overtone, and so on. This higher-order approach may find uses in barrier-tunneling problems in atomic and nuclear physics.

Quasi-Optical Power Combining of Solid-State Millimeter-Wave Sources

1986-02-01

J.W. Mink

Very efficient power combining of solid-state millimeter-wave sources may be obtained through the application of quasi-optical resonators and monotfthic source arrays. Through the theory of reiterative wavebeams (beam modes) with … Very efficient power combining of solid-state millimeter-wave sources may be obtained through the application of quasi-optical resonators and monotfthic source arrays. Through the theory of reiterative wavebeams (beam modes) with application of the Lorentz reciprocity theorem, it is shown that planar source arrays containing 25 individual elements or more result in very efficient power transfer of energy from the source arrays to the fundamental wave-beam mode. It is further shown that for identical sources within a properly designed quasi-optical power combiner, the output power tends to increase much faster that number of source elements.

Slow-wave launching at the lower hybrid frequency using a phased waveguide array

1976-02-01

M. Brambilla

The coupling efficiency of a phased multi-waveguide structure (the "Grill") designed to launch HF-waves at the lower hybrid resonance to heat large toroidal plasmas, while satisfying the accessibility condition, is … The coupling efficiency of a phased multi-waveguide structure (the "Grill") designed to launch HF-waves at the lower hybrid resonance to heat large toroidal plasmas, while satisfying the accessibility condition, is studied. To find the reflection and transmission coefficients, as well as the k||-spectrum of the excited field, the waveguide field, represented as a superposition of eigenmodes, is matched to the field in the plasma, which is evaluated on the assumption of a linear density profile near the plasma edge. It is found that the reflection coefficient can be made acceptably low and is not sensitively dependent on the plasma parameters. It is concluded that it is possible to design a Grill capable to launch lower hybrid waves at the power level required for the ignition of a reactor plasma.

Beam Transmission of Ultra Short Waves

1928-06-01

H. Yagi

Part I of this paper is devoted to a description of various experiments performed at wavelengths below 200 cm. Curves are given to show the effect of the earth and … Part I of this paper is devoted to a description of various experiments performed at wavelengths below 200 cm. Curves are given to show the effect of the earth and various types of inductively excited antennas called "wave directors." Part I is concluded with a discussion of beam and horizontally polarized radiation. Part II is devoted chiefly to the magnetron tubes used for the production of very short wavelengths (as low as 12 cm.) and the circuit arrangements employed. It is shown that the geometry of the tube and its external connections are of great importance. The effect of variation of plate voltage, magnetic field strength and other factors on the high-frequency output, is described.

Vacuum Electronic High Power Terahertz Sources

2011-08-25

John H. Booske , Richard Dobbs , Colin D. Joye +5 more

Recent research and development has been incredibly successful at advancing the capabilities for vacuum electronic device (VED) sources of powerful terahertz (THz) and near-THz coherent radiation, both CW or average … Recent research and development has been incredibly successful at advancing the capabilities for vacuum electronic device (VED) sources of powerful terahertz (THz) and near-THz coherent radiation, both CW or average and pulsed. Currently, the VED source portfolio covers over 12 orders of magnitude in power (mW-to-GW) and two orders of magnitude in frequency (from <; 0.1 to >; 10 THz). Further advances are still possible and anticipated. They will be enabled by improved understanding of fundamental beam-wave interactions, electromagnetic mode competition and mode control, along with research and development of new materials, fabrication methods, cathodes, electron beam alignment and focusing, magnet technologies, THz metrology and advanced, broadband output radiation coupling techniques.

Time-Frequency Analysis

1996-04-17

Time-frequency analysis has been carried out for microwave radiation from a virtual-cathode oscillator. The ob- jective is to observe and understand the frequency behavior of virtual-cathode oscillation. The diagnostic results … Time-frequency analysis has been carried out for microwave radiation from a virtual-cathode oscillator. The ob- jective is to observe and understand the frequency behavior of virtual-cathode oscillation. The diagnostic results have given clear evidence of mode hopping and frequency shifting. The dependence of mode competition on diode operation parameters is also identi- fied. Initial particle-in-cell simulations using MAGIC code have been carried out, and the results were in general agreement with those obtained in the experiments.

Electron Paramagnetic Resonance

1973-01-01

L. A. Sorin , M. V. Vlasova

THE PROPAGATION OF ELECTROMAGNETIC WAVES

1984-01-01

L.D. LANDAU , E.M. LIFSHITZ

State-of-the-Art of High-Power Gyro-Devices and Free Electron Masers

2020-01-01

M. Thumm

View PDF Chat

On the theory of two-dimensional stationary self-focusing of electromagnetic waves

1973-08-01

S. V. Manakov

Transition Radiation and Transition Scattering

1982-01-01

V. L. Ginzburg

Transition radiation is a process of a rather general character. It occurs when some source, which does not have a proper frequency (for example, a charge) moves at a constant … Transition radiation is a process of a rather general character. It occurs when some source, which does not have a proper frequency (for example, a charge) moves at a constant velocity in an inhomogeneous and (or) nonstationary medium or near such a medium. The simplest type of transition radiation takes place when a charge crosses a boundary between two media (the role of one of the media may be played by vacuum). In the case of periodic variation of the medium, transition radiation possesses some specific features (resonance transition radiation or transition scattering). Transition scattering occurs, in particular, when a permittivity wave falls onto an nonmoving (fixed) charge. Transition scattering is closely connected with transition bremsstrahlung radiation. All these transition processes are essential for plasma physics.

High-Power Microwave Sources and Technologies

2001-01-01

R.J. Barker , Edl Schamiloglu

Foreword by Dr. Delores Etter. Preface. Acknowledgments. List of Contributors. List of Acronyms and Abbreviations. Introduction. HPM Sources: The DOD Perspective. Gigawatt--Class Sources. Pulse Shortening. Relativistic Cerenkov Devices. Gyrotron Oscillators … Foreword by Dr. Delores Etter. Preface. Acknowledgments. List of Contributors. List of Acronyms and Abbreviations. Introduction. HPM Sources: The DOD Perspective. Gigawatt--Class Sources. Pulse Shortening. Relativistic Cerenkov Devices. Gyrotron Oscillators and Amplifiers. Active Plasma Loading of HPM Devices. Beam Transport and RF Control. Cathodes and Electron Guns. Windows and RF Breakdown. Computational Techniques. Alternative Approaches and Future Challenges. Index. About the Editors.

Waveguide Handbook

1986-01-01

N. Marcuvitz

The Gyrotron

1977-06-01

V.A. Flyagin , A. V. Gaponov , I. Petelin +1 more

This paper describes the genealogical tree of the gyrotron, stimulated emission of cyclotron radiation in microwave electronics from magnetron to gyrotron, and arrangement of the gyrotron. The structure of the … This paper describes the genealogical tree of the gyrotron, stimulated emission of cyclotron radiation in microwave electronics from magnetron to gyrotron, and arrangement of the gyrotron. The structure of the alternating field in the gyrotron is also given, along with motion and bunching of electrons near cyclotron resonance, equations of the gyrotron, and varieties of the gyrotron. A review of experimental studies is discussed, with problems of utilization of stimulated emission cyclotron radiation.

The return of the quartic oscillator. The complex WKB method

1983-01-01

A. Voros

High-power microwave sources

1987-01-01

V. L. Granatstein , I. Alexeff

COUPLING OSCILLATIONS OF LATTICES OF DIFFERENT DIELECTRIC RESONATORS

2025-06-24

А. А. Трубин | Information and Telecommunication Sciences

Background. The development of many elements of modern communication systems is increasingly based on the use of various types of dielectric resonators (DR). The theory of coupled oscillations of resonators … Background. The development of many elements of modern communication systems is increasingly based on the use of various types of dielectric resonators (DR). The theory of coupled oscillations of resonators is the basis for further calculations and optimisation of the scattering matrices of electromagnetic waves on various devices. When calculating devices built on a large number of resonators, direct numerical methods are often not effective. They usually require the use of powerful computers, therefore, the calculation of elements on a large number of DR is impossible without building analytical models of complex structures based on electrodynamic modelling. Objective. The study aims to find analytical expressions for the frequencies and distributions of electromagnetic fields of natural oscillations of lattices, consisting of a large number of various types of dielectric resonators for use in various devices of optical communication systems. To solve this problem, a linear system of equations, which relates the complex amplitudes and frequencies of the resonators, obtained earlier from the perturbation theory, was used. Methods. To find analytical expressions, methods of matrix theory are used. In this case, both known methods of calculating the determinants of tri-diagonal and circulant matrices are used, as well as their modifications related to the calculations of more complex matrices, which, after transformations, are reduced to much simpler formulas. The final result is the receipt of new general analytical formulas for describing coupled oscillations of lattices consisting of a large number of dielectric resonators of various types. Results. Coupled oscillations of one-dimensional linear lattices of two types of dielectric resonators are considered. New analytical expressions for complex frequencies and amplitudes of resonators, as well as Q-factor expressions without restrictions on their number, are obtained. A new model of natural oscillations of two-dimensional lattices, consisting of dielectric resonators of two different types, is constructed. General analytical solutions are found for the frequencies and amplitudes of coupled oscillations for two types of two-dimensional lattices with different arrangements of resonators. Analytical solutions are found for the amplitudes and frequencies of coupled oscillations of two axially symmetric ring lattices with different types of resonators, which are characterised by different placement symmetry in free space. The obtained general analytical expressions for the frequencies of coupled oscillations are compared with the results of calculations obtained numerically, by solving linear systems of equations. A very good agreement between the solutions obtained by the two methods is demonstrated. Conclusions. The developed theory is the basis for the design of many devices of the optical wavelength range, which are built on the basis of the use of a large number of dielectric resonators of various types. The obtained new analytical expressions for calculating coupled oscillations of dielectric resonators allow building new more efficient models of scattering for optimization of various optical communication devices.

Comprehensive Investigation of Fundamental Mode Profiles in Monolithic Nonplanar Ring Oscillators

2025-06-24

Weitong Fan , Chengfeng Ma , W. Li +5 more | Applied Optics

Scalar product for the radiation of resonant modes

2025-06-24

NULL AUTHOR_ID | Physical review. A/Physical review, A

A design for terahertz-driven isolated sub-femtosecond electron pulse

2025-06-20

Sha Zhu , Yushan Zeng , Xieqiu Yu +5 more | Applied Physics Express

Abstract Isolated electron pulses are pivotal in resolving ultrafast dynamics. In this study, we present a design for generating isolated ultrashort electron pulses using a terahertz resonator capable of achieving … Abstract Isolated electron pulses are pivotal in resolving ultrafast dynamics. In this study, we present a design for generating isolated ultrashort electron pulses using a terahertz resonator capable of achieving subfemtosecond pulse durations. Our numerical simulations demonstrate that terahertz field enhancement within the thin resonator could enable generation of isolated electron pulses as short as 817 attoseconds from a 500-fs pulse. The design can also be extended to direct current with two additional capacitors. We analyze key design parameters to provide empirical guidance for experimental implementations, with the potential of delivering ultrafast single electron pulses compactly and cost-effectively.

Periodic transient beam loading effect in triple radio-frequency systems

2025-06-20

NULL AUTHOR_ID | Physical Review Accelerators and Beams

Laser interaction and terahertz radiation generation in a longitudinally inhomogeneous plasma

2025-06-19

Ashish Yadav , K. Gopal , A. Vijay +1 more | Physica Scripta

Abstract This study demonstrates an analytic framework for generating terahertz (THz) radiation through the nonlinear interaction&#xD;of frequency-varying lasers with a longitudinally nonuniform plasma. When two lasers beat the plasma density&#xD;gradient … Abstract This study demonstrates an analytic framework for generating terahertz (THz) radiation through the nonlinear interaction&#xD;of frequency-varying lasers with a longitudinally nonuniform plasma. When two lasers beat the plasma density&#xD;gradient at an angle, it imparts an oscillatory velocity to the plasma electrons. Variation in laser amplitude creates a&#xD;non-linear ponderomotive force that oscillates at the beating frequency of the laser, typically within the THz range. This&#xD;force drives a non-linear current density in the plasma, with its transverse component contributing to the generation of&#xD;THz radiation. Using a frequency-varying laser prolongs the interaction time between the laser and the plasma, leading&#xD;to the production of broadband THz radiation. Optimizing key factors, such as the angle of the laser relative to the&#xD;plasma, its time-dependent frequency, and its intensity, allows the control of the THz radiation power. These optimized&#xD;conditions are essential for developing efficient THz sources for various practical applications

Simulation of Planar THz TWT with Sheet Beam Using 1-D Large Signal Model

2025-06-18

Vishnu Srivastava | IETE Technical Review

Resonant enhanced detection of the higher-order modes of a locked cavity

2025-06-13

R. Cabrita , A. W. Jones , J. V. van Heijningen +5 more | Optics Express

Chirped pulse waveguide amplifier

2025-06-12

Alexander Rudenkov , VLADIMIR KALASHNIKOV , Maxim Demesh +3 more | Optics Express

View PDF Chat

A new tuning method based on quantitative compensation for uniform and non-uniform travelling-wave accelerating structures

2025-06-01

Yu Yang , Bo Wang , Jia Yang +6 more | Results in Physics

KlyH: 1D Disk Model-Based Large-Signal Simulation Software for Klystrons

2025-05-30

Hezhang Zhao , Hu He , Shifeng Li +5 more | Electronics

This paper presents KlyH, a new 1D (one-dimensional) large-signal simulation software for klystrons, designed to deliver efficient and accurate simulation and optimization tools. KlyH integrates a Fortran-based dynamic link library … This paper presents KlyH, a new 1D (one-dimensional) large-signal simulation software for klystrons, designed to deliver efficient and accurate simulation and optimization tools. KlyH integrates a Fortran-based dynamic link library (DLL) as its computational core, which employs high-performance numerical algorithms to rapidly compute critical parameters such as efficiency, gain, and bandwidth. Compared with traditional 1D simulation tools, which often lack open interfaces and extensibility, KlyH is built with a modular and open architecture that supports seamless integration with advanced optimization and intelligent design algorithms. KlyH incorporates multi-objective optimization frameworks, notably the Non-Dominated Sorting Genetic Algorithm II (NSGA-II) and Optimized Multi-Objective Particle Swarm Optimization (OMOPSO), enabling automated parameter tuning for efficiency maximization and interaction length optimization. Its bandwidth-of-klystron-analysis module predicts gain and output power across operational bandwidths, with optimization algorithms further enhancing bandwidth performance. A Java-based graphical user interface (GUI) provides an intuitive workflow for parameter configuration and real-time visualization of simulation results. The open architecture also lays the foundation for future integration of artificial intelligence algorithms, promoting intelligent and automated klystron design workflows. The accuracy of KlyH and its potential for parameter optimization are confirmed by a case study on an X-band relativistic klystron amplifier. Discrepancies observed between 1D simulations and 3D PIC (three-dimensional particle-in-cell) simulation results are analyzed to identify model limitations, providing critical insights for advancing high-performance klystron designs.

Radiation of a sequence of high-power S-band microwave pulses by a system of two gyromagnetic lines with saturated ferrite in a scheme with repeated use of a high-voltage pulse

2025-05-28

V. Yu. Konev , Pavel V. Priputnev , Roman K. Sobyanin +2 more | Russian Physics Journal

Experimental analysis of metamaterial integrated applicator for hyperthermia cancer treatment

2025-05-28

Nitika Sharma , Rajesh Khanna , Hari Shankar Singh +1 more

Design and start-to-end beam dynamics simulation of the first super-radiant THz free-electron laser source in Thailand

2025-05-27

Natthawut Chaisueb , S. Rimjaem

Development of a slotted waveguide antenna for lower hybrid fast wave coupling in KSTAR plasmas

2025-05-24

J. Jo , S. H. Kim , Hyunho Wi +2 more

An integrated simulator towards a digital twin for MW-class Gyrotrons for fusion reactors

2025-05-24

Elia Novarese , Antonio Cammi , Rosa Difonzo +2 more

Electron pressure drives THz phonons in metal-metal superlattices

2025-05-23

Matias Bargheer , Jan‐Etienne Pudell , Marc Herzog +7 more

<title>Abstract</title> Light controlled strain engineering of functional quantum materials and modulation of materials at THz frequencies are two formidable challenges of nanotechnology. Cheap and robust metal-metal superlattices, where periodic repetitions … <title>Abstract</title> Light controlled strain engineering of functional quantum materials and modulation of materials at THz frequencies are two formidable challenges of nanotechnology. Cheap and robust metal-metal superlattices, where periodic repetitions of bilayers - each layer a few atoms thick - are deposited by simple sputtering, constitute thermoacoustic meta-materials. These meta-materials are largely underexplored, because the free electrons in metals are thought to delocalize even beyond the optical penetration depth. We use ultrafast X-ray diffraction to prove that in Pt/Cu SLs, the energy of optically excited electrons is rapidly localized in the Pt layers, faster than the electron-phonon coupling. The energy of the hot electron gas is confined to a few nm in Pt, although it is in direct contact with Cu. The concomitant ultrafast electron pressure drives coherent THz strain waves with a giant 1$\%$ lattice deformation. The frequency can be tailored by the sputtered SL structure, enabling new schemes of ultrafast strain-mediated resonant nano-(spin)-electronics.

State-of-the-Art of High-Power Gyro-Devices: 2025 Update of Experimental Results

2025-05-23

M. Thumm

Abstract This report presents an update of the experimental achievements published in the review “State-of-the-Art of High-Power Gyro-Devices and Free Electron Masers,” Journal of Infrared, Millimeter, and Terahertz Waves, 41, … Abstract This report presents an update of the experimental achievements published in the review “State-of-the-Art of High-Power Gyro-Devices and Free Electron Masers,” Journal of Infrared, Millimeter, and Terahertz Waves, 41, No. 1, pp 1–140 (2020) related to the development of gyro-devices (Tables 2–34). Emphasis is on high-power gyrotron oscillators for long-pulse or continuous wave (CW) operation and pulsed gyrotrons for many other applications. In addition, this work gives a short update on the present development status of frequency step-tunable and multi-frequency gyrotrons; coaxial-cavity multi-megawatt gyrotrons; complex two-section stepped cavity gyrotrons; gyrotrons for technological and spectroscopy applications; relativistic gyrotrons; large orbit gyrotrons (LOGs); quasi-optical gyrotrons; fast- and slow-wave cyclotron autoresonance masers (CARMs); gyroklystron, gyro-TWT, and gyrotwystron amplifiers; gyro-harmonic converters; gyro-BWOs; and dielectric vacuum windows for such high-power mm-wave sources. Gyrotron oscillators (“gyromonotrons or just gyrotrons”) are mainly used as high-power millimeter-wave sources for electron cyclotron heating (ECH), electron cyclotron current drive (ECCD), stability control, and diagnostics of magnetically confined plasmas for clean generation of energy by controlled thermonuclear fusion. Megawatt-class gyrotrons employ synthetic-diamond output windows and single-stage depressed collectors (SDCs) for electron energy recovery. The maximum pulse length of the 140 GHz, 1.3 MW IPP-KIT-THALES gyrotron is 3 min (1.2 MW/6 min) at 97.5% Gaussian output mode purity and 47% efficiency. The 1 MW version of this tube operates at pulse lengths up to 30 min, and PLL-frequency stabilization has been demonstrated. The first Japan QST-CANON 170 GHz ITER gyrotron prototype achieved 1 MW, 800 s at 55% efficiency and holds the energy world record of 2.88 GJ (0.8 MW, 60 min, 57%). The Russian 170 GHz ITER gyrotron obtained 0.99 (1.2) MW with a pulse duration of 1000 (100) s and 57 (53)% efficiency. First frequency-injection-locked operation of a very high-order-mode Russian 170 GHz-1 MW gyrotron (IAP) has been demonstrated in short pulses using a PLL-frequency-stabilized 20 kW gyrotron master oscillator. A Russian short-pulse 74.2 GHz, 100 kW gyrotron (SPbSTU) with 4-stage depressed collector achieved an efficiency of 72%. The prototype tube of the KIT 2 MW, 170 GHz coaxial-cavity gyrotron (pulse duration 50 ms) achieved in 1 ms pulses the record power of 2.2 MW at 48% efficiency and 96% Gaussian mode purity and was operated at pulse lengths up to 50 ms. High-power CW gyrotron oscillators have also been successfully used in materials processing. Such technological applications require tubes with the following parameters: f ≥ 24 GHz, P out = 4–50 kW, CW, η ≥ 30%. Gyrotrons with pulsed magnet for various short-pulse applications deliver P out = 210 kW with τ = 20 µs at frequencies up to 670 GHz (η $$\cong$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>≅</mml:mo> </mml:math> 20%), P out = 5.3 kW at 1 THz (η = 6.1%), and P out = 0.5 kW at 1.3 THz (η = 0.6%). The average powers produced by 94 GHz gyroklystrons, gyrotwystrons, and gyro-TWTs are 10 kW, 5 kW, and 20 kW, respectively.

Experimental demonstration of tractor millimeter wave beam propulsion

2025-05-20

M. Takahashi , Toshiki Yamada , R. Minami +2 more

A high-power oscillation test of a dual-frequency 1-MW gyrotron

2025-05-20

Konan Yagasaki , S. Kobayashi , Sosuke Ando +7 more

An annular explosive cathode with a shielding ring for the X-band high-impedance relativistic klystron amplifier

2025-05-19

Danni Zhu , Meng Jin , Yancheng Cui +3 more

Abstract High impedance (>1 k) relativistic klystron amplifiers (RKAs) are able to avoid power capacity limitations with higher conversion efficiency, compared with low impedance RKAs. An annular explosive cathode is … Abstract High impedance (>1 k) relativistic klystron amplifiers (RKAs) are able to avoid power capacity limitations with higher conversion efficiency, compared with low impedance RKAs. An annular explosive cathode is investigated to offer moderate density electron beams for an X-band high-impedance RKA. Instead of a traditional solid thermionic cathode applied to a high-impedance RKA, the annular explosive cathode is able to simplify and minimize its conventional electron optics system. Nevertheless, the impedance of explosive cathode is hardly to achieve as high as k level. A shielding ring is introduced to realize the high impedance of 1.15 k and reduce the surface electric ﬁeld on unexpected explosive emission region. Analysis of the explosive cathode employed in the X-band high-impedance RKA are described. The fine performance of this RKA is demonstrated by 2.5-D particle-in-cell (PIC) simulations. The typical microwaves with a power of 100 MW are generated at a frequency of 11.424 GHz when the beam voltage and current are 527 kV and 457 A respectively, under a guiding magnetic ﬁeld of 0.55 T. The corresponding power conversion efficiency and gain are as high as 42 % and 50 dB.

A Design of Modulator Power Supply and Pulse Modulator Circuit for a Conventional Traveling Wave Tube Amplifier

2025-05-19

Jitendra Kumar Shukla , Kailash Kushwaha , Rajiv Kumar Singh

A TM01-TE11 Circular Waveguide Mode Converter on the Basis of Dielectric Filling

2025-05-16

Zibin Weng , Ziming Lv , Linsen Zan +2 more

In this paper, a dielectric-filled circular waveguide TM01-TE11 mode converter is proposed, which has high conversion efficiency and a wide operating bandwidth. Filling the circular waveguide with dielectric material changes … In this paper, a dielectric-filled circular waveguide TM01-TE11 mode converter is proposed, which has high conversion efficiency and a wide operating bandwidth. Filling the circular waveguide with dielectric material changes the local propagation characteristics, thus achieving a phase difference between the TE11 modes in the two halves of the circular waveguide during propagation. This, in turn, facilitates the completion of mode conversion with high efficiency. Compared with the conventional radial dielectric plate, this paper improves the method of filling the dielectric inside the circular waveguide by transforming it into a coaxial structure. This is followed by the incorporation of a radial dielectric plate, a modification that has been proven to enhance the conversion efficiency and extend the operational bandwidth. The mode converter operates at 9.7 GHz, and when the dielectric filler material is polytetrafluoroethylene (PTFE), both simulation and practical studies are carried out. The simulation results demonstrate that the maximum conversion efficiency of this mode converter is 99.2%, and the bandwidth with conversion efficiency greater than 90% is nearly 21.1%. The maximum conversion efficiency in the actual test is essentially consistent with the simulation results. The validity of the design scheme of this converter and the accuracy of the simulation study are demonstrated.

Propagating discrete breather due to plane wave in electrical transmission lattice with imaginary resistance

2025-05-15

Pierre Anselme Simo Motcheyo , Rosalie Laure Woulaché , E. Tchomgo Felenou +2 more

Abstract We examined the discrete nonlinear Schrödinger (DNLS) equation as a voltage on a discrete electrical line in the presence of an imaginary resistance. The continuous approximation of the steady … Abstract We examined the discrete nonlinear Schrödinger (DNLS) equation as a voltage on a discrete electrical line in the presence of an imaginary resistance. The continuous approximation of the steady state allows for acquiring a static breather, whose amplitude decreases when the imaginary resistance increases. The linear stability and the full integration lead to seeing that the breather is stable when the centre is in the middle of the lattice, but becomes unstable when it's near the edge. The analytical amplitude of the static discrete breather matches very well with the numerical supratransmission threshold. A method for propagating discrete breathers is proposed. To achieve this, a static and unstable breather is shaken by periodic excitation of the chain with very small amplitude. By using a method, single and two traveling waves can be generated in the DNLS equation. This is not the case with the classical nonlinear band gap studies.

Design, fabrication, and test of a parallel-coupled slow-wave high-gradient structure for short input power pulses

2025-05-15

NULL AUTHOR_ID

Self-Compression of Microwave Superradiance Pulses During Their Interaction with Flows of Unperturbed Cyclotron Oscillators

2025-05-13

N. S. Ginzburg , Lev A. Yurovskiy , I. V. Zotova +1 more

Femtosecond Thulium Fiber Laser Utilizing a Gain Switched Laser Diode

2025-05-13

Ibrahim Abughazaleh , Matthew Gerard , Panuwat Srisamran +3 more

Spinoptics in the Kerr spacetime: Polarized wave scattering

2025-05-12

NULL AUTHOR_ID

Field dispersion in uniformly‐excited radial parallel plate waveguides for a compact proton accelerator design

2025-05-12

Morgan J. Maher , C. Lund , Julien Bancheri +2 more

Abstract Background Proton therapy (PT) is a beneficial modality for treating certain cancers but remains under utilized due in part to the high cost of existing PT devices. Dielectric wall … Abstract Background Proton therapy (PT) is a beneficial modality for treating certain cancers but remains under utilized due in part to the high cost of existing PT devices. Dielectric wall accelerators (DWAs) are a proposed class of coreless induction accelerators that may present a suitable option for compact and affordable PT. To realize a compact device, acceleration modules must be designed to achieve field strengths approaching 100 MV/m delivered as pulses on the order of nanoseconds. Purpose Here, we examine pulse injection into radial parallel plate waveguides as a means of producing high‐intensity, pulsed accelerating fields. We present an approach for understanding the impact of waveguide properties on electromagnetic dispersion as well as a means of accounting for this dispersion to produce suitable accelerating fields. Methods Geometric and material properties for a set of waveguides were identified based on existing literature and commonly available materials. An analytic model is presented to describe how waveguide geometry and material affect electromagnetic dispersion in a waveguide. Simulations performed in COMSOL Multiphysics are used to calculate a transfer function for the set of waveguides, which provide a means of determining the waveguides output for arbitrary inputs and vice versa. The simulation results are compared to the analytic solution and used to explore alternate matching conditions at the beampipe of the accelerator. Results Overall, radial waveguides provide a passive enhancement of the injected pulse, with enhancement of high‐frequency components found to be proportional to the square root of the ratio of outer radius to inner radius of the waveguide. Dispersion in the waveguide caused by the radial propagation of the pulse depends on multiple waveguide properties (outer radius, inner radius, material) and leads to reduced enhancement at lower frequencies. The field enhancement in the waveguides reduces the peak voltage required to achieve the desired accelerating field strength. However, dispersion alters the temporal profile of the applied pulse, resulting in a distorted field at the inner radius. Using the transfer function, it is possible to determine the shape of the pulse required to achieve a suitable accelerating field for a given waveguide design. Conclusions Passive field enhancement occurred in all waveguides and across all frequencies studied in this work. As such, radial parallel plate waveguides could help to reduce the high voltages required from upstream switching networks. The analytic model can be used to select waveguide parameters that provide a suitable enhancement of the upstream voltage pulse to achieve the high field strengths required for a compact accelerator. However, pulse dispersion must be accounted for. If upstream pulse shaping can be achieved to account for electromagnetic dispersion in the waveguide, pulse injection into radial parallel plate waveguides could be a suitable mechanism for field generation in a DWA.

Start-to-end simulation for a compact terahertz free electron laser with a beam chopper system

2025-05-09

Roger Luo , Qushan Chen