Electron Cyclotron Resonance Maser Research Articles

Synchrotron radiation loss of a laser accelerator based on an inverse electron cyclotron resonance maser.

A laser accelerator based on an electron cyclotron resonance maser is described. Important losses that give rise to saturation length and saturation power are included in the analysis. The results are compared with results from an inverse free-electron laser accelerator.

Development of simulation tools for numerical investigation and computer-aided design (CAD) of gyrotrons

As the most powerful CW sources of coherent radiation in the sub-terahertz to terahertz frequency range the gyrotrons have demonstrated a remarkable potential for numerous novel and prospective applications in the fundamental physical research and the technologies. Among them are powerful gyrotrons for electron cyclotron resonance heating (ECRH) and current drive (ECCD) of magnetically confined plasma in various reactors for controlled thermonuclear fusion (e.g., tokamaks and most notably ITER), high-frequency gyrotrons for sub-terahertz spectroscopy (for example NMR-DNP, XDMR, study of the hyperfine structure of positronium, etc.), gyrotrons for thermal processing and so on. Modelling and simulation are indispensable tools for numerical studies, computer-aided design (CAD) and optimization of such sophisticated vacuum tubes (fast-wave devices) operating on a physical principle known as electron cyclotron resonance maser (ECRM) instability. During the recent years, our research team has been involved in the development of physical models and problem-oriented software packages for numerical analysis and CAD of different gyrotrons in the framework of a broad international collaboration. In this paper we present the current status of our simulation tools (GYROSIM and GYREOSS packages) and illustrate their functionality by results of numerical experiments carried out recently. Finally, we provide an outlook on the envisaged further development of the computer codes and the computational modules belonging to these packages and specialized to different subsystems of the gyrotrons.

Analysis and Design of the Resonator in a 110 GHz Gyrotron Oscillator

Gyrotron oscillators are powerful millimeter, sub-millimeter and even potential THz wave sources, capable of reaching megawatt power levels. They are widely studied today to use for electron cyclotron resonance heating, current drive, stability control and active diagnostics of magnetically confined fusion plasmas. To suppress the parasitic modes and improve the efficiency of the over-mode resonator is a important object for the design of high power gyrotrons. On the basis of electron cyclotron resonance maser theory and generalized transmission line theory, we compiled programs to analyze the resonant cavity in a 110 GHz gyrotron. The results shows that the coupling coefficient to parasitic modes of gradually tapered cavity is obviously less than line-joint cavity. By calculating and studying different gradual-varying and line-joint resonant cavities, we designed a gradually tapered resonator for a 110 GHz gyrotron, which is good at suppressing the parasitic modes, improving the purity of the operating mode and the efficiency of the beam–wave interaction.

Efficiency Enhancement of Coaxial-Cavity Electron Cyclotron Resonance Maser by Tapering Guide Magnetic Field

A coaxial-cavity cyclotron resonance maser (CRM) oscillator with tapered guide magnetic field is proposed. It is shown that the transmission quality can be improved by tapering the guide magnetic field. Simulation indicates that the efficiency of a millimeter-wave gyrotron oscillator may be reached up to 38.7% by optimizing the tapered magnetic field.

Basic theoretical formulation of plasma microwave electronics. II. Kinetic theory of electron beam-wave interactions

For pt.I see ibid., vol.28, no.6, p.2135-51 (2000) Building upon the theoretical foundations presented in Part I of this paper, the kinetic theory of electron-beam-wave interactions in a magnetized plasma-filled waveguide (MPW) is presented in this second part. This kinetic theory treatment is more generally applicable to cases of less-intense electron-beams (Montgomery and Tidman, 1964). The dispersion relations for longitudinal and transverse interactions, in both smooth and corrugated waveguides, are all derived by using kinetic theory to model the e-beam dynamics. This includes kinetic theory treatments of the plasma filled electron cyclotron resonance maser (ECRM) and a combination of Cherenkov-cyclotron resonance phenomena. It is important to note that in an MPW, transverse interactions (e.g., ECRM interactions) are always coupled with longitudinal interactions. Using the kinetic treatment is essential for studying the ECRM because its energy conversion mechanism is based on azimuthal phase bunching and finite Larmor radius effects. The dispersion relation that we derive shows that the presence of a plasma-fill tends to increase the growth rate of the waveguide mode ECRM instability.

Basic theoretical formulations of plasma microwave electronics. I. A fluid model analysis of electron beam-wave interactions

This two-part paper presents the first complete, generalized basic theoretical formulation for electron beam-wave interactions in a plasma-filled (corrugated or smooth-walled) waveguide immersed in a finite magnetic field. The general interaction and dispersion equations of the longitudinal and transverse interactions in both smooth and corrugated magnetized plasma-filled waveguides (MPWs) are formulated. Our approach differs from that of previous investigators in that we begin by first deriving the dispersion relation of an MPW and then using the resulting electromagnetic fields, which embody the plasma effects, as the basis field vectors. We then investigate the underlying interactions with a superimposed electron-beam in a variety of microwave device configurations. For example, we examine plasma Cherenkov radiation, the plasma-filled travelling-wave-tube/backward-wave-oscillator (TWT/BWO), the plasma-filled electron cyclotron resonance maser (ECRM), and other beam-wave interactions including those involving ion-channels. Some possible new interactions in a magnetized plasma-filled waveguide (MPW) are proposed. A detailed discussion and analysis of the important physical role of the plasma background are given. Many interesting features of beam-wave interactions in an MPW are pointed out, three of them being most essential. One is that transverse interactions are always accompanied by longitudinal interactions. The second is that the magnetized plasma itself is strongly involved in the interaction mechanisms via an additional component of the field. The third interesting feature is that the plasma-filled ECRM prefers to operate at high cyclotron harmonics. The first part of this two-part paper presents formulations using a fluid model for both the plasma and the beam. It also includes a detailed treatment of the physical effects of the ion channel that is formed in the plasma by an intense electron beam. Part II extends the analyzes by retaining a fluid treatment for the plasma-fill but substituting a kinetic theory treatment for the electron beam. This kinetic theory model should be used when the velocity spread of the beam's electrons must be taken into account. The theory presented in both parts of this paper is based upon the "given field" approach that has been widely used successfully in science and technology, in particular in microwave electronics. In both parts of the paper, sample numerical calculations are also presented in order to illustrate the physics.

Two Mechanisms in a Relativistic Electron Cyclotron Maser with a Special Quasioptical Cavity

In a relativistic electron cyclotron maser with an axisymmetrical quasioptical cavity of oblique rotation at arbitrary angle, the rotating angle has a great influence on beam-wave interaction. Two different physical mechanisms are found with the rotating angle ranging from 0° to 90°. One is cyclotron auto-resonance maser regime for small angle, with small optimized external magnetic field; the other is electron cyclotron resonance maser regime for large angle, with comparatively large optimized magnetic field.

The effect of electron beam geometric deformation errors on the small-signal characteristic of ECRM

In this paper is studied the effect of electron beam geometric deformation errors on the small — signal characteristics of the TE mn o mode Electron Cyclotron Resonance Maser (ECRM), based on the elliptically cross—sectional e—beam deformation model. As an example, the effect of small geometric deformation errors on the TE 01 o mode fundamental ECRM coupling coefficient is quantitatively shown.

Space charge effects and stability of electron motion in the electrostatic electron cyclotron resonance maser

Abstract The paper deals with the space charge effects and the stability of electron motion in the electrostatic electron cyclotron resonance maser (EECRM). The complete dispersion equation of EECRM is obtained and two types of instability included in it are analysed. The results indicate that: (a) there exists a critical value for the electrostatic potential which affects the inherent oscillation in the EECRM system; (b) the frequency of the inherent oscillation increases when the DC space charge effect is taken into consideration; (c) the inherent oscillation instability may still exist in non-relativistic mode; and (d) the space charge effect is conducive to the synchronous instability and it increases the growth rate of instability.

Operation and theory of a driven single-mode electron cyclotron maser.

A study is made of the operation of the electron cyclotron resonance maser (ECRM), when subjected to an external rf signal. The signal is introduced both via direct injection through a coupling hole in the oscillator and by modulating the electron beam in separate cavities, upstream of the oscillator. Experiments using both one and two ``prebunching'' cavities are reported. It is experimentally found that the gyromonotron, a specific embodiment of the ECRM, can be phase locked by premodulating the electron beam at drive power levels more than two orders of magnitude below that predicted by Adler's widely applicable theory for single-cavity oscillators. A perturbation theory is used to predict the phase-locking frequency band for a gyromonotron with any number of prebunching cavities. The predictions of this theory agree with the experimental results for two- and three-cavity phase locking. An investigation is made into the general amplitude and frequency response of the ECRM to an applied external signal. Experimentally, three distinct regions of qualitatively different ECRM behavior are noted: soft excitation, which is free, self-excited oscillation; hard excitation, where the oscillation requires an external impulse for startup; and amplifier, in which the output power level and frequency are linearly related to the drive in the small-signal regime.

Electrostatic electron cyclotron resonance maser with slotted coaxial waveguide

A new scheme of the electrostatic electron cyclotron resonance maser with slotted coaxial waveguide is presented here. Having studied it both in the linear and non linear regimes, we found that the radiation frequency and the converting efficiency could be increased largely for the low-energy electron beam in this scheme. The maximum converting efficiency of electrons with the π azimuthal mode can reach 23%. It has been revealed that there exist azimuthal and radical electron benching phenomena, corresponding to the kinetic and potential energy converting processes of electrons with the RF field. This revelation is helpful when looking into the physics of the electrostatic electron cyclotron resonance masers and other kinds of microwave devices with an electrostatic centrifugal field

Free-electron laser–electrostatic electron cyclotron resonance maser hybrids

The free-electron laser (FEL)–electrostatic electron cyclotron resonance maser (EECRM) hybrids, a new kind of FEL comprised of a relativistic electron beam and an electrostatic centrifugal field, are presented and studied in this paper. In a fluid dynamical linear theory, the dispersion equation for transverse electromagnetic (TEM) mode operation is derived, analyzed, and numerically solved. It is found both analytically and numerically that FEL instability occurs near beam resonance [(ωl−klv∥)2−ω2p (γ−2∥ −β2∥β2⊥φ̇20/ Ω2l)=0]. However, FEL instability near cyclotron resonance (ωs−ksv∥ =±(2−β2⊥)1/2φ̇0) is not found in the TEM mode analysis.

The orbit theory of electrostatic electron cyclotron resonance masers

The orbit theory of the electrostatic electron cyclotron resonance maser (EECRM), which is similar to the orbitron maser, is presented based on models with both circular and noncircular steady-state electron orbits. In contrast to the nonlinear theory of the magnetostatic electron cyclotron resonance maser (MECRM), the concept of converting efficiency is introduced. The efficiencies for TE, TM, and TEM modes are calculated in various cases. Numerical analyses show that in the interaction process the radio-frequency (RF) fields attract energy mainly from the potential energy of electron beams. The nonlinear interaction mechanisms and the effects of some parameters are also studied.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Electrostatic electron cyclotron resonance maser (linear theory)

The linear theory of electrostatic electron cyclotron resonance maser (EECRM) is given in this paper. Starting from the fundamental concept, we obtained the perturbed equation of relativistic electron motion in an electrostatic centrifugal system, and the dispersion equation for both TEmn and TMmn modes of the EECRM have been derived with detailed discussion for the infinitely thin beam layer. The nonrelativistic case has also been studied. Digital calculations show that the dispersion curves of the EECRM are similar in shape to that of the conventional electron cyclotron resonance maser (MECRM) and the magnitude of growth rate of the EECRM is comparable with that of MECRM. Although the dispersion equation of EECRM contains a special kind of singularity [ω−k∥v∥−(m±(2−β2⊥)1/2) ω0 =0], the relevant instability within the parameter region of our calculations in this paper has not yet been found; this problem remains to be studied in the future.

Double-stream electron cyclotron maser

Abstract A new mechanism for stimulated radiation combining the cyclotron instability with the plasma double-stream instability is presented. It can be regarded as a new type of electron cyclotron resonance maser (ECRM) (Hirshfield 1979, Liu 1979) as well as a two-stream free-electron laser (FEL) (Piestrup 1981, Bekefi and Jacobs 1982) in a broader sense. One can say that this device combines ECRM and the two-stream FEL into one. The linear theory of the double-stream ECRM is given. Numerical calculations show that it offers the attractive advantages of high gain and broadband as compared with the conventional ECRM.

Gyrotron or electron cyclotron resonance maser: An introduction

The gyrotron or electron cyclotron resonance maser is a high-power microwave source in which the microwave fields gain energy from a beam of relativistic electrons. In this article, an elementary account of the gain mechanism based on a linear, small-signal analysis is presented.

The kinetic theory of the electron cyclotron resonance maser with space charge effect taken into consideration

The kinetic theory of the electron cyclotron resonance maser is given in this paper with the space charge effect and non-resonance cyclotron harmonics taken into consideration. The dispersion equations have been calculated using a digital computer and the influence of these factors are discussed in detail.