Showing papers in "International Journal of Electronics in 1986"
TL;DR: In this paper, first-order magnetron injection gun (MIG) design trade-off equations are given for use in obtaining an adequate starting point for gun simulations on the computer.
Abstract: First-order magnetron injection gun (MIG) design trade-off equations are given for use in obtaining an adequate starting point for gun simulations on the computer. These equations are based on conservation of angular momentum and adiabatic electron flow and they contain relativistic corrections for high voltage design. The equations provide considerable insight into the basic physical processes by which gyro-cyclotron beams are formed and controlled. They have also proven very useful in design feasibility studies of high power MIGs. Two examples of MIG designs are given in which these equations were utilized.
215 citations
TL;DR: In this article, a comprehensive theory of the cyclotron resonance maser (CRM) interaction in a circular waveguide is presented, and the conditions for maximum temporal and spatial growth rates are shown.
Abstract: This paper presents a comprehensive theory of the cyclotron resonance maser (CRM) interaction in a circular waveguide. The kinetic theory is used to derive the dispersion relationships for both TE and TM modes. The TE mode case has been investigated by several authors, but there has been comparatively little work on the TM mode case. However, the TM mode interaction competes effectively with the TE mode interaction at relativistic electron energies. The conditions for maximum temporal and spatial growth rates are shown. The TM mode growth rates are found to vanish when the RF wave group velocity equals the beam axial velocity (‘grazing incidence’). The single particle theory is used to derive a compact set of self-consistent non-linear equations for the TE and TM mode interactions. These equations are particularly appropriate for the cyclotron auto-resonance maser (CARM) regime but applicability extends to other regimes as well. The conditions for optimum efficiency are investigated for oscillator and amp...
178 citations
TL;DR: In this article, a non-stationary theory is developed for gyrotrons with open resonators that have a minimum diffraction Q. The gyrotron is described by a self-consistent set of equations taking into account the dependence of the axial structure of microwave oscillations on the electron beam.
Abstract: A non-stationary theory is developed for gyrotrons with open resonators that have a minimum diffraction Q. The gyrotron is described by a self-consistent set of equations taking into account the dependence of the axial structure of microwave oscillations on the electron beam where electron bunching is defined by the same axial structure. As a result of non-stationary processes constant-amplitude oscillations are established for a moderate value of the beam current. As the beam current grows, automodulation and stochastic oscillations take place; their spectral characteristics are presented. It is shown that in the region of parameters close to optimum for efficiency constant-amplitude oscillations are established in gyrotrons with low-Q resonators.
146 citations
TL;DR: In this paper, a quasi-optical hybrid mode can be generated from TE 0n gyrotron mode compositions by the two multi-step mode conversion processes: (1) TE0n to TE01 to TE11 to HE11 or (2) ΣTE 0n toTE01 to TM 11 to HE 11).
Abstract: Efficient plasma heating by ECR-wave irradiation requires axisymmetric, narrow, pencil-like millimetre wave beams with well-defined polarization. The linearly polarized gaussian-like HE11, mode satisfies these conditions best. This quasi-optical hybrid mode can be generated from TE0n gyrotron mode compositions by the two multi-step mode conversion processes: (1) ΣTE0n to TE01 to TE11 to HE11 or (2) ΣTE0n to TE01 to TM11 to HE11. The first scheme has the advantage that the converters can all be made without bends, allowing an arbitrary choice and fast change of the polarization plane. The second scheme does not exhibit this advantage, but it is more suitable at very high frequencies (e.g. 140GHz) because efficient TE01-to-TM11 transducers can be made considerably shorter than serpentine TE01-to-TE11 mode converters. This paper presents computations on mode converter systems of the first type at 70GHz and of both types at 140GHz (ID = 27 · 8 mm for 200kW transmission lines). The structure of wall perturbati...
68 citations
TL;DR: In this paper, the authors calculate the resonant frequency, Q-value and field profiles of a tapered gyrotron resonator, taking into account the coupling of modes induced by the taper.
Abstract: The paper shows the calculation of the resonant frequency, Q-value and field profiles of the eigenmodes of tapered gyrotron resonators, taking into account the coupling of modes induced by the taper. The mode coupling is negligible for taper angles of only a few degrees, but must be taken into account if the taper angle exceeds about 10°.
66 citations
TL;DR: In this paper, a coupled-rate-equation model of a semiconductor laser incorporating bimolecular recombination and realistic injection current pulse shapes is presented, and theoretical predictions are found to be in excellent agreement with the experimental results.
Abstract: Stable production of 15ps pulses having a peak power of 200 mW from fully gain-modulated, unbiased GaAs double-heterostructure and multiple-quantum-well lasers emitting in the 08 μm-09 μm wavelength range and from InGaAsP double heterostructure lasers emitting in the 12 μm-13 μm range is reported The shortest pulses obtained from GaAs DH lasers show a width as small as 2ps The optical pulses represent the first relaxation oscillation of the laser Special double avalanche generators are developed to produce large injection-current pulses with widths down to 12Sps at repetition rates up to 10 MHz Numerical and approximate analytical solutions of a coupled-rate-equation model of a semiconductor laser incorporating bimolecular recombination and realistic injection current pulse shapes are presented The theoretical predictions are found to be in excellent agreement with the experimental results
52 citations
TL;DR: In this paper, the operating characteristics of high power relativistic magnetron injection guns (MIGs) were studied theoretically and a set of analytic expressions based on adiabatic approximations for a coaxial diode was used to identify feasible design regions in parameter space.
Abstract: The operating characteristics of high power relativistic magnetron injection guns (MIGs) are studied theoretically. A set of analytic expressions based on adiabatic approximations for a coaxial diode is used to identify feasible design regions in parameter space. Particle simulations are then used to optimize particular designs. Results for a µs, 100 MW, 500 kV MIG, designed for an X-band gyroklystron, are critically examined.
50 citations
TL;DR: In this paper, the results of tests on a Varian 140 GHz CW gyrotron are presented and compared with theoretical predictions, as well as those of the output power and efficiency.
Abstract: The results of tests on a Varian 140 GHz CW gyrotron are presented. In initial pulse tests on the tube, an output power of 100 kW was achieved at 28% efficiency in the desired TEU0 031 cavity mode. Under CW operating conditions, the tube achieved an output power level of 75 kW at 31% efficiency. This is the highest CW power level ever obtained at a frequency above 100 GHz in a microwave tube. During CW tests, measurements of the ohmic losses in the interaction circuit were made and the temperature of the output window was monitored. These measurements, as well as those of the output power and efficiency, are presented and compared with theoretical predictions. Future experimental 140 GHz tubes will employ alternate electron gun and interaction cavity designs. The benefits of these design changes are discussed in the context of achieving higher output power levels and efficiencies.
40 citations
TL;DR: In this paper, a rate-equation analysis of a diode laser in an external resonator which is actively mode-locked by periodic modulation of the injection current is presented.
Abstract: A rate-equation analysis of a diode laser in an external resonator which is actively mode-locked by periodic modulation of the injection current is presented. A computer simulation of the transient process of pulse generation is developed. The coupled rate equations for electron and photon densities as functions of time and position within the diode are solved numerically. The effects of sinusoidal and pulsed injection current, spatial and temporal gain saturation, various resonator configurations, mismatch between modulation frequency and round-trip frequency, and varying laser parameter values are considered. A comparison of results with those of previous theories is presented. Optimum conditions for mode-locking are stated.
37 citations
TL;DR: In this article, the effects of self-consistent AC space charge on an electron beam in the form of a plane sheet with all the gyrocentres aligned were investigated.
Abstract: The effects of self-consistent AC space charge are investigated by means of an integral equation for an electron beam in the form of a plane sheet with all the gyrocentres aligned. It is found that the Bernstein mode instability (Hirschfield 1981, Mourier 1980, Charbit et al. 1981) persists for such beams, even in the absence of a cavity surrounding the beam, provided that the beam temperature is not too large (thermal broadening of the resonance) or extremely small (high density stabilization). An eigenvalue condition where electromagnetic effects are included shows how the Bernstein modes couple with cavity modes and how the resonance with an electromagnetic wave can occur. Implications for quasi-optical gyrotrons are discussed.
34 citations
TL;DR: In this paper, the AC and DC transverse self-fields are calculated in gyrotron oscillators using a slow time scale hamiltonian formalism, and the principal effect of AC self-field is to couple electromagnetic and electrostatic effects so as to increase the growth rate.
Abstract: The AC and DC transverse self-fields are calculated in gyrotron oscillators. A slow time scale hamiltonian formalism is developed and utilized. The principal effect of AC self-fields is to couple electromagnetic and electrostatic effects so as to increase the growth rate. The main effect of DC self-fields is to generate a spread in gyrofre-quencies which tends to reduce efficiency.
TL;DR: In this paper, the design of polarization converters to minimize mode conversion in overmoded waveguides for applications such as gyrotron outputs and electron cyclotron heating (ECH), and give examples for TE11, TM11 and TE23 modes.
Abstract: Small deformations with suitable azimuthal symmetry can be used to convert between rotating and stationary polarizations of any given mode in circular waveguides. Special cases include converters from linear polarization to circular or elliptical polarization, and rotators of linear polarization through arbitrary angles. Rotating (corkscrew type) deformations may also be used to convert between unpolarized TE0m modes and rotating TEpm modes. Polarization converters may be useful in single-mode (TE11) or overmoded waveguides. We consider the design of polarization converters to minimize mode conversion in overmoded waveguides for applications such as gyrotron outputs and electron cyclotron heating (ECH), and give examples for TE11, TM11, and TE23 modes. The performance of a TM11 elliptic polarizer fabricated for an ECH experiment is reviewed. Explicit formulas for all of the needed coupling coefficients are collected in an appendix for reference.
TL;DR: In this article, different structures, alignment techniques and performance of autocorrelation systems for the measurement of picosecond pulses generated by injection lasers suitable for optical communications are reviewed.
Abstract: The paper reviews briefly the different structures, alignment techniques and performance of autocorrelation systems for the measurement of picosecond pulses generated by injection lasers suitable for optical communications The interpretation of results obtained with such systems is also discussed Specific reference is made to a system operating at 1-3 μm wavelength The aim is to provide a helpful account of such systems for those starting in the field of picosecond electronics In order to illustrate the technique some new results are presented on mass-transport injection lasers with low thresholds
TL;DR: In this paper, a self-consistent field slow-time scale model and computer code for gyroklystron simulation and analysis has been developed and applied to a representative three-stage CW gyroknysstron design, where the RF magnetic field interaction and provision for velocity distribution in the electron beam have been included in the formulation.
Abstract: A self-consistent field slow-time scale model and computer code for gyroklystron simulation and analysis has been developed and applied to a representative three-stage CW gyroklystron design. The RF magnetic field interaction and provision for velocity distribution in the electron beam have been included in the formulation. The results of the simulation reveal the presence of interesting non-linear hysteresis-like features in the drive curve and frequency response under certain experimental conditions. Significant degradation of the device gain and efficiency characteristics is observed to occur for velocity spreads above 8%.
TL;DR: In this paper, a novel analytical model for the threshold voltage of long-channel MOSFETs with implanted channels is presented, where the analytical difficulty posed by the gaussian function to solve Poisson's equation has been removed by the use of a new integrable function that closely fits with the Gaussian and a doping transformation based on a piecewise averaging approximation.
Abstract: A novel analytical model for the threshold voltage of long-channel MOSFETs with implanted channels is presented. The model is simple from a computational point of view and yields accurate values of the threshold voltage, if the implant profile is gaussian. The analytical difficulty posed by the gaussian function to solve Poisson's equation has been removed by the use of a new integrable function that closely fits with the gaussian and a doping transformation based on a piecewise averaging approximation. The use of this function opens the way to a new technique of modelling semiconductor devices with gaussian doping. The threshold voltage and the profiles of potential and electric field inside the channel are calculated from their closed-form expressions for different doping and biasing conditions. The accuracy of the model is established by comparison with the results of the numerical solution for a gaussian doped channel and some experimental results. The possibilities of extending the model to short-cha...
TL;DR: In this article, a review of reported results for optical bistability in semiconductors, with especial reference to that occurring in laser structures, is given, and estimates are made of likely improvements that may occur in power-speed trade-offs for these devices.
Abstract: A review is given of reported results for optical bistability in semiconductors, with especial reference to that occurring in laser structures. Estimates are made of likely improvements that may occur in power-speed trade-offs for these devices. It is concluded that laser amplifier bistability offers comparable or, in some cases, better total energy budgets than for other forms and has the useful attribute of optical gain. However, extreme wavelength sensitivity and difficulty in forming large two-dimensional arrays using today's technology mitigate against use of the amplifier for large-scale optical logic. These two factors may be avoided by the use of self-electro-optic effect devices (SEEDs), which are less wavelength-sensitive, and by multiple-quantum-well dispersive etalons in the case of requirements for large amounts of parallel processing.
TL;DR: In this paper, the relationship between facet reflectivity and gain bandwidth in semiconductor optical amplifiers is discussed and the first high-resolution measurements of the gain spectrum of InGaAsP 1.5 µ amplifiers are presented.
Abstract: We discuss the relationship between facet reflectivity and gain bandwidth in semiconductor optical amplifiers and present the first high-resolution measurements of the gain spectrum of InGaAsP 1 · 5 µ optical amplifiers. The relatively smooth gain spectrum and high output power of near-travelling-wave amplifiers are compared with those of Fabry-Perot amplifiers.
TL;DR: In this paper, the first-order building blocks, using only operational transconductance amplifiers and capacitors, are realized and studied, and the circuits exhibit convenient control of circuit parameters with the help of external voltage or current control.
Abstract: Electronically controlled first-order building blocks, using only operational transconductance amplifiers and capacitors, are realized and studied. The circuits exhibit convenient control of circuit parameters with the help of external voltage or current control. Each circuit uses a low component count and has low sensitivity performance. The basic blocks can be used for the realization of higher-order electronically tunable filters.
TL;DR: In this article, the efficiency of a gyrotron resonator as a function of resonator geometry, applied magnetic field and electron beam parameters is studied in the adiabatic cold cavity fixed field approximation.
Abstract: The efficiency of a gyrotron resonator as a function of resonator geometry, applied magnetic field and electron beam parameters is studied in the adiabatic cold cavity fixed field approximation. The results are used as a guide for the selection of design parameters for experiments at the Kernforschungszentrum Karlsruhe, West Germany. Criteria for selection were good efficiency over an extended power range, smooth start-up behaviour and power control, and mode stability.
TL;DR: In this article, the relativistic intense electron beam regime was considered and a design procedure based on one-dimensional planar or conical models for electron flow in diodes was presented.
Abstract: Most gyrolron electron gun designs are based on the use of electron trajectory codes; however, the complexity of the problem is such that a design procedure using only a simulation code can be very tedious and expensive. For these reasons one dimensional approximations to the flow are extremely useful. Such one dimensional flows can be used to synthesize first approximations to the electrode shapes. The purpose of this paper is to show how previous work on this technique for non-relativistic beams can be extended to the relativistic intense electron beam regime. The analysis is based on four one-dimensional planar or conical models for electron flow in diodes. The planar models are relativistic and can be used to obtain electrode shapes for space charge limited flow. The conical models shed light on important geometric effects. Principally, it is shown that the space charge limited current is larger in realistic geometries than in the corresponding planar configuration. A design procedure based o...
TL;DR: In this article, a single cavity oscillator at 35 GHz has been developed, which can produce tubes for higher frequencies and higher powers in the frequency range from 28-70 GHz with output powers of 200-kW or more in pulses of 0-1-1/1 second.
Abstract: High efficiency (~40%) gyrotrons have been built by other workers in the frequency range from 28–70 GHz with output powers of 200 kW or more in pulses of 0 · 1–1 second, and some have operated in CW. In this frequency range, we have developed a single cavity oscillator at 35 GHz. Table 2 includes a summary of results obtained with this tube. Of course, it is required to produce tubes for higher frequencies and higher powers. According to the laws of electron dynamics and electromagnetics in vacuo, simple scaling in frequency requires a scaling in dimensions with invariant voltages, currents, and powers. Most quantities in that case are not invariant, e.g. electric field E ~ƒ, magnetic induction B ~ ƒ, current density J ~ ƒ, power density J ~ƒ2, power density due to electron impact (Pel/S) ~ƒ2,Rf ohmics losses, assuming classical skin effect ~ƒ5/2, and losses in dielectric present complex variation with frequency depending upon their nature. This type of scaling cannot be applied indefinitely to higher fre...
TL;DR: In this paper, a Langer transformation is used to obtain an approximate solution for problems with two turning points in terms of a uniform expansion valid for all axial positions; for the fundamental mode, the RF field longitudinal distribution is essentially of the form exp [w2(z)/2], where W(z) is determined by the resonator profile.
Abstract: Open resonators are considered with longitudinal profiles described by continuous and sufficiently smooth functions in order to reduce reflections and mode conversion in the cavity. For these types of resonators, it is shown that the single mode approximation is adequate. Using a Langer transformation, the approximate solution for problems with two turning points is given in terms of a uniform expansion valid for all axial positions; for the fundamental mode, the RF field longitudinal distribution is essentially of the form exp [—w2(z)/2], where W(z) is determined by the resonator profile. A comparative study, of the resonant and selective properties, for different resonator types is made, and the influence of the cavity profile upon the electric field longitudinal distribution is analysed. As an example of practical interest, the design of a resonant cavity for a 35 GHz gyrotron operating in the TE021 mode is presented.
TL;DR: In this paper, the linearized self-consistent theory of gyrotron is analytically treated for a self-excited oscillator with non-fixed structure, consisting of four waves, namely the forward and backward travelling waves of the waveguide, and two electron cyclotron waves.
Abstract: The linearized self-consistent theory of gyrotron is analytically treated for a self-excited oscillator with non-fixed structure. The self-consistent RF axial field profile consists of four waves, namely the forward and backward travelling waves of the waveguide, and two electron cyclotron waves. According to the magnetic field value (or the detuning parameter), the electron cyclotron wave couples strongly with the forward wave, or weakly with backward wave of the waveguide mode. Also, the starting current and the axial field profile are significantly different for the forward versus the backward interaction.
TL;DR: In this paper, a multimode simulation of the frequency spectrum of a quasi-optical 120 GHz gyrotron with a small mirror separation is presented, which presents a large separation between the frequencies of the modes.
Abstract: We have performed a multimode simulation of the frequency spectrum of a quasi-optical 120 GHz gyrotron with a small mirror separation (d = 5 cm) which, therefore, presents a large separation between the frequencies of the modes (δω/ω= 2 · 5%). It appears that under this condition multimode equilibrium is quite frequent. However, even if single mode equilibrium is not achieved, the electronic efficiency η remains high: under all magnetic field profiles its maximum reaches about 30%, and is equal to or exceeds the maximum single mode efficiency.
TL;DR: In this article, a boundary integral Green's function technique was devised to calculate eigenfunctions and eigenvalues of open resonators in two dimensions, which damp exponentially in time, but diverge in space.
Abstract: A boundary integral Green's function technique is devised to calculate eigenfunctions and eigenvalues of open resonators in two dimensions. These eigenfunctions damp exponentially in time, but diverge in space. The cavity Q's of a variety of open resonators are calculated and compared with experimental cold tests.
TL;DR: In this paper, the effect of thermal spread in pitch angle on the limiting current of an electron beam is calculated. And the downstream beam parameters are also evaluated, including the pitch angle and the downstream thermal spread.
Abstract: The effect of thermal spread in pitch angle on the limiting current of an electron beam is calculated. The downstream beam parameters are also evaluated. At the limiting current the downstream value of the pitch angle and the downstream thermal spread are found to be sensitive to the initial thermal spread.
TL;DR: In this paper, a detailed theory based on the two-layered cavity model is presented for the annular-ring microstrip antenna with an air gap between the substrate and the ground plane.
Abstract: A detailed theory based on the two-layered cavity model is presented for the annular-ring microstrip antenna with an air gap between the substrate and the ground plane. Comparison between theory and experiment is given.
TL;DR: A TE1, 3 gyrotron with an output power of 300kW was designed and tested in this article, and the results of the experimentation were given, and a comparison with theory is made.
Abstract: A TE1, 3 gyrotron to operate at 85 GHz with an output power of 300 kW has been designed, fabricated and tested. The device is described and results of the experimentation are given. A comparison with theory is made. Operation at the design frequency was achieved and output powers approaching 200 kW with efficiencies of 30% have been obtained.
TL;DR: In this paper, the relative permittivity and conductivity of forest vegetation on radiowaves were measured by fitting the theoretical model to the measured data on lateral wave attenuation constant derived from the height gain measurements conducted in forest, in the frequency range of 50-800 MHz.
Abstract: Many experiments have been carried out to study the absorption and scattering properties of forest vegetation on radiowaves but very little has been reported on the measurements of relative permittivity (∊r) and conductivity (σ) of forest slab. Due to various constraints, the in-situ measurements of ∊, and σ were limited to 75 MHz. Inverse methods have reportedly been employed to evaluate ∊ r and σ for forest slab from the experimental data on the measurements of antenna pattern, reflection coefficient, wave impedance, and path loss, etc. These studies were restricted to 400 MHz. In this paper the values of ∊ r and σ for the forest slab have been estimated by fitting the theoretical model to the measured data on lateral wave attenuation constant derived from the height-gain measurements conducted in forest, in the frequency range of 50–800 MHz.
TL;DR: In this paper, a gyrotron where the large-orbit electron beam is focused by the axial magnetostatic field and an assistant radial electrostatic field is proposed, and a kinetic analysis is given.
Abstract: This paper proposes a gyrotron where the large-orbit electron beam is focused by the axial magnetostatic field and an assistant radial electrostatic field. A kinetic analysis is given. Numerical calculation is carried out which indicates that the growth rate may increase.