PLASMA-FILLED DIELECTRIC CHERENKOV MASER WITH A LONGITUDINAL MAGNETIC FIELD

The use of a background plasma in a dielectric Cherenkov maser can effectively increase the efficiency and the microwave output power of the device. Here, the effect of the longitudinal uniform magnetic field on the wave-beam interaction of the plasma-filled dielectric Cherenkov maser is examined by solving the beam-plasma, dielectric lined waveguide dispersion equation. And the effects of the longitudinal magnetic field, plasma density and dielectric parameters on the linear spatial growth rate and the energy ratio are presented.     

Linear theory of a large-orbit electron cyclotron maser

By using of the perturbation approach, a large-orbit electron cyclotron maser is investigated in this paper. The perturbed motion of a relativistic electron and dispersion equation for both gyrotron and gyro-peniotron are obtained, then some discussions are carried out.     

On the kineteic theory of electron cyclotron maser

This paper starts from the kinetic theory to expound the method of characteristics. Influence of the equilibrium distribution functionf _o upon analyzed result is fully investigated. Dispersion equation is rigorously derived in waveguide coordinate system in case of interaction between TE _mn field in a circular waveguide and a single momentum ring-shaped electron beam. In the meantime, we make some critical review of previous papers and clarify their confusion and ambiguities.     

On the kinetic theory of electron cyclotron maser

This paper starts from the kinetic theory to expound the method of characteristics. Influence of the equilibrium distribution functionf ₀ upon analyzed result is fully investigated. The dispersion equation is regorously derived in a waveguide coordinate system in case of interaction between TE _mn field in a circular waveguide and a single-momentum ring-shaped electron beam. In the meantime, we make some critical review of previous papers and clarify their confusion and ambiguities.     

Cherenkov radiation in a plasma-filled coaxial cylindrical dielectric slow-wave structure

In this paper, a new type of plasma-filled coaxial cylindrical dielectric slow-wave structure that is very beneficial to the beam-wave interaction of the high-power microwave source is developed. The Cherenkov radiation in the plasma-filled coaxial cylindrical dielectric slow-wave structure is examined by use of the self-consistent linear field theory. The dispersion equation and the synchronized condition as well as the wave growth rate of the beam-wave interaction are derived. The dispersion equation clearly shows that the Cherenkov radiation excited in the plasma-filled coaxial cylindrical dielectric slow-wave structure results from the coupling between the slow electromagnetic wave, TM-modes, propagated along the slow-wave structure and the negative-energy space-charge wave propagated along the relativistic electron beam. The numerical results indicate that the dispersion curves are divided into two branches due to the presence of the background plasma in the coaxial cylindrical dielectric slow-wave structure for the identical electromagnetic wave mode, and the radial distributions of the longitudinal fluctuating electric field corresponding to the two dispersion curve branches are completely different. Injection of the background plasma into the slow-wave structure can enhance the output frequency and the wave growth rate of the beam-wave interaction and enables the high-power microwave source that utilizes this kind of slow-wave structure to gain more output power of the microwave with higher output frequency.     

A time-dependent non-linear theory of ion channel electron cyclotron maser

A time-dependent non-linear theory is developed for ion channel electron cyclotron maser (ICECM), and the corresponding numerical calculation results are given for the first time. The theoretical analysis shows that the longitudinal plasma wave tends to enhance the energy exchange between the beam and wave. Using the numerical calculation of the self-consistent time evolution of scattering wave growth, the non-linear effect of ion density on the beam-wave interaction efficiency has been studied. The time norm, which must be satisfied in the operation of ICECM, is verified. Taking 6.8?×?10¹³?cm^?3 ion density, 1?MV accelerated voltage and 1.5?KA beam current, the present numeric calculation results show that the pulse scattering wave power and the frequency can achieve about 200?MW and 284?G?rad/s respectively.     

Linear theory of an electron cyclotron maser operating at the fundamental

The linear theory of an electron cyclotron maser (ECM) operating at the fundamental is developed. A set of analytic expressions, valid for all TE cavity modes, is derived for the starting current and frequency detuning using the Vlasov-Maxwell equations in the weakly relativistic limit. These results are applicable for an arbitrary electron velocity distribution as well as any longitudinal distribution of the RF field. It is shown that the starting current can be expressed in a simple form which contains the Fourier trans-form of the longitudinal field distribution. Analytic results are presented for specific longitudinal field variations, including uniform, sinusoidal, and Gaussian. It is found that the starting characteristics of an ECM are strongly influenced by the axial dependence of the RF field, but weakly affected by the velocity spread of the electron beam. The problem of multimode oscillation is treated in the linear theory by using a Slater expansion of the cavity field. The complete formulation for mode competition based on this expansion is presented and preliminary results are derived. This comprehensive analysis of ECM linear theory should be useful as a diagnostic of ECM performance and should facilitate comparison between theory and experiment.     

Self-consistent theory of cyclotron autoresonance maser in a uniform planar waveguide

A general dispersion relation for the cyclotron autoresonance maser (CARM) that takes into account self-consistent couplings between TE, TM and ac space charge perturbations in a uniform planar waveguide is derived. The dispersion relation predicts enhanced growth rate due to ac space charge effects. Results from computer simulations of a planar CARM amplifier are presented to support this finding.     

Vector coupled-mode theory of dielectric waveguides

A consistent derivation of a system of vector coupled-mode (VCM) equations for parallel dielectric waveguides is presented and compared with earlier versions of the improved coupled-mode theory (ICMT). As a validity test, it is shown that the effectively scalar transverse electric and transverse magnetic (TM) coupled-mode (CM) equations are direct limits of our full VCM formulation. In particular, our formulation does not lead to the fundamental error found with earlier coupled-mode theories (CMTs) in a case of TM fields. Functional equations of our VCMT are consistent with Maxwell's equations and lead to higher precision. They can be applied to complicated arrays of strongly coupled parallel dielectric waveguides with true vectorial behavior.     

A unified theory of the diocotron, cyclotron maser, and negative-mass instabilities

A small-signal theory is developed which simultaneously includes the diocotron, negative mass, and cyclotron maser effects. The simple analysis is performed using a Pierce type approach for an axis encircling electron beam inside a circular waveguide. Relativistic, nonrelativistic, synchronous, and nonsynchronous limits are considered to recover the individual instabilities. It is found that the diocotron and the negative mass/cyclotron maser effect strengthen each other. At voltages higher than a few kiloelectron volt the relativistic negative mass/ cyclotron maser effects become dominant. However, the threshold beam voltage, which appears in gyrotron literature, for the onset of the cyclotron maser instability is found absent when the diocotron effect is taken into account. The feasibility of building a low-voltage tube is explored.     

Field behavior near a dielectric wedge

A review of the theory of field behavior near a dielectric wedge is presented. An overview of the static results is given, and it is shown that the series of Meixner for the dynamic case in general is nonexisting. Numerical results for scattering by a dielectric cylinder of square cross section indicate that the static results give an accurate account for the rate of growth of the fields in the singular cases, but some disagreement in nonsingular cases.     

On the electron equilibrium distribution function in the kinetic theory of electron cyclotron maser

The problems concerning the specification of electron equilibrium distribution function for the kinetic theory of ECRM are investigated in this paper. After detailed analysis of the published equilibium distribution functions, several conclusion have been achieved.     

Synchrotron resonance maser

Attention is drawn to an obscure formula derived from relativistic quantum electrodynamics in the mid-'60s by Sokolov and Ternov for induced absorption and emission from highly relativistic electrons in a static uniform magnetic field. From their results, we develop handy formulae and graphs to help in preliminary designs for radiation sources to operate at high synchrotron harmonics. Approximate design parameters are given for 100 kW oscillators operating at wavelengths below 3mm, employing magnetic fields of less than 12 kG. It is shown that the Sokolov-Ternov formula can also be deduced from classical relativistic plasma wave theory, but for a numerical factor in one term. This term is shown to describe a gain mechanism which has apparently received scant notice in the gyrotron literature.     

Field singularities at the tip of a dielectric cone

Data are given on the nature of the singularities near the tip of a dielectric cone of circular cross section. For a "sharp" cone the singularity is associated with avarphi-independent potential; for a "reentrant" cone with a "cos varphi" type of potential.     

An electromagnetic theory of dielectric waveguides with multipleembedded cylinders

We consider a dielectric waveguide or optical fiber having a real isotropic ambient refractive index. In addition, several isotropic and uniform embedded cylindrical regions of differing refractive index are considered. The radii, refractive indexes, and positions of the cylindrical subregions are arbitrary. We establish a rigorous method of determining the fields and propagation constants for the vector electromagnetic modes supported by this structure. We verify the accuracy of the method by comparing its results with those of other authors in particular cases, and exhibit direct demonstrations of convergence     

Field acceleration factor for dielectric breakdown of MOS devices

In this paper a model is presented for estimating the field acceleration factor for dielectric breakdown of SiO₂. Using the observation that the total charge through the oxide is invariant (for MOS capacitors fabricated by identical process steps) and assuming that the I-V characteristic is dominated by Fowler Nordheim tunneling prior to breakdown, a simple expression for the acceleration factor can be obtained. The expression gives a good fit to experimentally obtained acceleration factors in the literature. It also indicates that the acceleration factor is field dependent such that the logarithm of acceleration factor vs field is not a straight line and care is required while extrapolating the results of accelerated testing.     

Field near the interface of a jungle dielectric slab

The transmitted far field of a short vertical dipole located in a jungle dielectric medium is evaluated by the steepest-descent technique. At near-grazing angles of transmission, the technique is modified to account for the influence of the branch point. The influence is found significant only in the field amplitude and is confined within a short distance from the jungle-air interface, within which the difference between the path of the geometric-optical wave and that of the lateral wave is less than a wavelength.     

Double-stream electron cyclotron maser

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.