Cyclotron Resonance Maser Research Articles

Ferrite-guided cyclotron-resonance maser.

The concept of a cyclotron-resonance maser (CRM) with a ferrite loading incorporated in its waveguide is proposed. The CRM interaction occurs between the rotating electron beam and the em wave propagating along a longitudinally magnetized ferrite medium. The ferrite anisotropic permeability resembles the CRM susceptibility in many aspects, and particularly in their similar response to the axial magnetic field (the ferrite susceptibility can be regarded as a passive analog of the active CRM interaction). The ferrite loading slows down the phase velocity of the em wave and thus the axial (Weibel) mechanism of the CRM interaction dominates. The ferrite loading enables also a mechanism of spectral tunability for CRM's. The ferrite loading is proposed, therefore, as a useful ingredient for high-power CRM devices. A linear model of the combined ferrite-guided CRM interaction reveals its useful features. Future schemes may also incorporate ferrite sections functioning as isolators, gyrators, or phase shifters within the CRM device itself for selective suppression of backward waves and spurious oscillations, and for gain and efficiency enhancement.

Carm-amplifier in the regime of "nonresonant" trapping of the electron beam

A new version of the regime of electron trapping is proposed for gyro-amplifiers. The use of this regime in the cyclotron resonance maser with a weakly relativistic electron beam can simultaneously provide efficiency as high as 50%, a very broad (tens of percent) frequency band, and very weak sensitivity to the spread in electron velocity.

A microwave gyro amplifier with a ferroelectric cathode

A ferroelectric cathode is employed for the first time as the electron-beam source in a microwave amplifier tube. A PLZT 12/65/35 ferroelectric ceramic with a high dielectric constant (/spl epsiv//sub r//spl sim/4000) is used in a form of a hollow cathode. The tube is operated in poor vacuum conditions (2/spl times/10/sup -5/ Torr) at room temperature, in a mechanism of a cyclotron-resonance maser amplifier. The device operates near the waveguide cutoff frequency at 6927 MHz. A 22-dB electronic gain and a 25-W output power are measured in this experiment.

Microwave annealing for ultra-shallow junction formation

We propose a new method for activation of source/drain junctions by microwave annealing. A study with B/BF2 implants at ultralow energies (300/500 eV) and high doses (1E15/5E15 cm−2) was completed. The samples were subjected to a high-power cyclotron resonance maser, called a “gyrotron,” for annealing. There appears to be some evidence of electromagnetic field-aided activation. The activation levels achieved exceed the levels reported by thermal means at the corresponding temperatures. Secondary ion mass spectroscopy (SIMS) was used to examine the impurity profile after ion implantation and diffusion. Spreading resistance profiling was used to examine the activated dopant profile.

Phase and gain measurements in a distributed-loss cyclotron-resonance maser amplifier.

The control of gain and phase delay in a cyclotron-resonance maser (CRM) amplifier is essential for a variety of applications. In this experiment, the gain and phase-delay variations are measured with respect to controlling parameters; the electron-beam current and the axial magnetic field. Following Chu et al. [Phys. Rev. Lett. 74, 1103 (1995)], the CRM amplifier comprises of a distributed-loss waveguide to enable high gain without oscillations. Our experiment yields an amplification up to 26 dB, and a phase-delay control range of 360 degrees. In order to keep a fixed gain with the varying phase delay, the two controlling parameters (i.e., the solenoid field and the beam current) are operated together in a compensating mode. The experiment is conducted in a frequency of 7.3 GHz, with an electron beam of 18-kV voltage and 0.25-0.4-A current. The experimental results are compared with a theoretical model. Practical implementations of gain and phase control in CRM devices are discussed.

Anomalous free electron laser interaction

Free electron lasers (FELs) are considered, typically, as fast wave devices. The normal FEL interaction satisfies the tuning condition ω≅( k z + k W) V z , where ω and k z are the em-wave angular frequency and longitudinal wave number, respectively, V z is the electron axial speed, and k W is the wiggler periodicity. This paper presents an anomalous FEL interaction, which may occur in slow-wave FELs (i.e. loaded by dielectric or periodic structures). The anomalous FEL effect presented here satisfies the tuning condition ω≅( k z − k W) V z , and it resembles the anomalous effect in slow-wave cyclotron resonance masers. A necessary condition for the anomalous interaction is ω/ k z < V z (i.e., the em-wave phase velocity should be slower than the electron beam). The paper presents a preliminary experimental result demonstrating the anomalous FEL effect in a stripline dielectric-loaded FEL experiment. A linear Pierce equation is applied to describe both the anomalous and normal FELs in the same framework. The paper is concluded with a conceptual discussion.

Influence of an External Signal on Self-Oscillations in the Distributed System “Helical Electron Beam—Backward Electromagnetic Wave”

We study the synchronization of oscillations in an active distributed system comprising a helical electron beam interacting with a backward wave in a waveguide (backward-wave cyclotron resonance maser). The characteristics of nonautonomous spatio-temporal oscillations in a system with different degrees of nonisochronism of oscillating electrons are examined. The physical processes accompanying the transition of a distributed self-oscillatory system to the synchronization mode are considered.

High-repetition-rate ferroelectric-cathode gyrotron

The intensive research on ferroelectric electron-emission mechanisms in the last decade has resulted in a wide understanding of the physics and characteristics of this plasma-assisted electron source. Nevertheless, practical devices employing this cathode were hardly introduced. In this experimental study, a high-repetition-rate microwave oscillator based on a ferroelectric electron gun has been developed. The device operates as a cyclotron-resonance maser in the gyrotron mode. Microwave pulses exceeding 1.5 kW at ∼7 GHz are measured in repetition rates above 3 MHz and duty cycles of ∼50%. These experimental results encourage the implementation of ferroelectric cathodes in practical high-power microwave tubes.

Cyclotron resonance maser with a tapered magnetic field in the regime of "nonresonant" trapping of the electron beam.

A different version of the regime of electron trapping is proposed for electron microwave amplifiers. The use of this regime in a cyclotron resonance maser with a weakly relativistic electron beam can simultaneously provide efficiency as high as 50%, a very broad (tens of percent) frequency band, and very weak sensitivity to the spread in electron velocity.

Effect of electron-beam momentum spread on cyclotron resonance maser operation at two resonant frequencies.

We present a theoretical analysis of cyclotron resonance maser (CRM) operation at two resonant frequencies including the effects of momentum spread in the electron beam. A linear analysis of the system equations is presented in the limit of small momentum spreads. Numerical solutions to the system equations are also given and are in agreement with the linear theory. The results predict that for realistic momentum spreads, operation of the CRM at the higher of the two resonant frequencies should be possible, extending its operating frequency range. An experiment currently under development at Strathclyde University is described and modeled numerically.

Cooperation of traveling and quasi-cutoff waves in a cyclotron-resonance maser

A new version of a cyclotron-resonance maser is studied theoretically and experimentally. Here, a spatially periodic helical electron beam couples traveling (autoresonance) and quasi-cutoff (gyrotron) waves of the same frequency, interacting with them at different cyclotron harmonics. The theory and early experimental results show that this maser can effectively generate a traveling wave with low quasi-cutoff wave excitation losses using a very simple feedback system.

Cyclotron resonance maser experiments in a bifilar helical waveguide

Oscillator and amplifier cyclotron-resonance-maser (CRM) experiments in a spiral bifilar waveguide are presented in this paper. The slow-wave CRM device employs a low-energy low-current electron beam (2-12 keV, approximately 0.5 A). The pitch angle of the helical waveguide is relatively small; hence, the phase velocity in this waveguide, V(ph) congruent with0.8c (where c is the speed of light), is much faster than the axial velocity of the electrons, V(ez)</=0. 2c. Thus traveling-wave-tube-type interactions are eliminated in this device. According to the CRM theory, the dominant effect in this operating regime, V(ez)<V(ph)<c, is the axial (Weibel) bunching mechanism rather than the opposed azimuthal bunching mechanism. In an oscillator mode, the CRM output frequency is tuned continuously in the range 2.5-8.4 GHz by varying the axial magnetic field. A fine-tuning is possible by the electron accelerating voltage. In the amplifier mode, this CRM experiment demonstrates an amplification up to 16 dB at 5 GHz. The immediate gain bandwidth is wider than 0.1 GHz (>2%). The wide tunable range of this CRM device due to the nondispersive bifilar helix is discussed.

Effective Co-generation of opposite and forward waves in cyclotron-resonance masers

A novel type of the frequency-tunable oscillator based on simultaneous generation of the forward and opposite waves at the same frequency, but at different cyclotron harmonics, is proposed. A spatially periodic helical electron beam allows for strong coupling of the waves. The opposite wave provides the broadband feedback and electron bunching, whereas the forward wave amplifies the arising signal and withdraws the rf power from the interaction region. A 15% efficiency and 5% frequency bandwidth have been achieved in the first experiment.

Effective coupling of cyclotron autoresonance maser and "gyrotron" modes on a phase-synchronized electron beam

For a cyclotron resonance maser (CRM) with a helical axis-encircling electron beam, the possibility of a strong interaction between cutoff (gyrotron) and traveling Doppler-up-shifted (cyclotron autoresonance maser) modes, which are in resonance with the electrons at the same frequency, is demonstrated. This effect can be used in a CRM oscillator of a new type, where the feedback and the mode selectivity for the operating traveling mode are provided due to the excitation of the cutoff mode. According to both the theory and the experiment, such a scheme can provide an effective excitation of the traveling mode with negligibly low losses associated with the cutoff mode.

Theoretical explanation and experimental observation of effective cyclotron coupling of traveling and near-cutoff modes on a phase-synchronized electron beam

For a Cyclotron Resonance Maser (CRM) with a helical axis-encircling electron beam, the possibility of a strong interaction between cutoff (gyrotron) and traveling Doppler-up-shifted Cyclotron Autoresonance Maser (CARM) modes, which are in resonance with the electrons at the same frequency, is demonstrated. This effect can be used in a CRM-oscillator of a new type, where the feedback and the mode selectivity for the operating traveling mode are provided due to the excitation of the cutoff mode. According to both the theory and experiment, such a scheme can provide an effective excitation of the traveling mode with negligibly low losses associated with the cutoff mode.

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.

The Axially Modulated, Cusp-Injected, Slowly Varied Section Opened Cavity, Magnicon Amplifier

I introduce a novel hybrid microwave amplifier that utilizes the axial bunching mechanism of klystrons in conjunction with the energy extraction mechanism of cyclotron resonance masers on TM mode. A simpler analytic model is used to show the viability of the device configuration and to explore limitations of the scheme. An example of an 11.5 GHz, fourth harmonic amplifier is presented. Adopting a multi-particle in azimuth range of (0, π/2) whose divide thickness of beam into three share approach, numerical simulation are used to demonstrate bunching in physical space and to estimate system efficiency et al. It shall be shown that this configuration enables the design of eficient, high harmonic devices over a wide range of parameters. Magnicon [1]-[11] is a kind of microwave amplifier tabe, it operates on the mode of rotating En10 in cylindrical cavity and there is solid focus fine electrons beam. In it from theory, the paper researches the new type magnicon, it is changed into using annular electron beam and using slowly variable section opened cavity. Compared with magnicon, its pervence beams will may be increased, its frequency may be increased up to millimeter wave band, its bandwidth also will may be increased same times. Than model of new type magnicon is put forward. Starting from large signal's theory, interacting of the annular electron beam into driver cavity in between the mode of rotating En10, numerical value to simulate. It done on the small current density and small density of electron in space that electrons dynamic are simulated, which may uses Runge-Kutta method to do it.

Cyclotron-resonance maser in a periodically loaded quadrupole transmission line

A cyclotron-resonance maser (CRM) is implemented in a periodic quadrupole waveguide. The device oscillates at the fundamental and high harmonics of the cyclotron frequency. This CRM employs a tenuous low-energy electron beam ( approximately 10 keV, 0.2 A). The periodic structure consists of an array of disks along the quadrupole transmission line, hence it combines both azimuthal and axial periodicities. This waveguide responds as a band-pass filter (BPF) with uniformly spaced passbands. The CRM is tuned to operate when the cyclotron harmonic frequencies coincide with the waveguide passbands. Microwave emission is observed at the first passband ( approximately 2.4 GHz), and simultaneously at the second and third harmonics in the corresponding BPF passbands ( approximately 4.9 and approximately 7.4 GHz, respectively). A polarized detector reveals the circular polarization of the em wave inside the tube. The results of this experiment may lead to the development of novel CRM harmonic generators and CRM arrays.

Cyclotron-resonance maser in a magnetic mirror.

A cyclotron-resonance maser (CRM) experiment is performed in a high-gradient magnetic field using a low-energy electron beam ( approximately 10 keV/1 A). The magnetic field exceeds 1.63 T, which corresponds to a 45-GHz cyclotron frequency. The CRM radiation output is observed in much lower frequencies, between 6.6 and 20 GHz only. This discrepancy is explained by the finite penetration depth of the electrons into the growing magnetic field, as in a magnetic mirror. The electrons emit radiation at the local cyclotron frequency in their reflection point from that magnetic mirror; hence, the radiation frequency depends mostly on the initial electron energy. A conceptual reflex gyrotron scheme is proposed in this paper, as a CRM analogue for the known reflex klystron.