Phase locking and bandwidth in a gyrotron oscillator

For imaging radar and for satelitte and space communication (e.g. NASA's deep space network), it is important that the bandwidth be as large as possible. Here we derive a formalism for computing the phase locking bandwidth that can be achieved in a gyrotron oscillator while varying the beam voltage. As an example, a second harmonic TE_02/03 gyrotron is considered. For this device, the effective bandwidth can be increased by a factor of about 3 compared with the fixed voltage case by allowing the beam voltage to change together with the input locking signal.     

Results from gyrotron backward wave oscillator experimentsutilizing a high-current high-voltage annular electron beam

We report the first gyrotron-backward-wave oscillator experiments which utilize a high-current (1-4 kA) high-voltage (300-500 keV) annular electron beam. The experiment was designed to operate in the TE₀₁ backward wave mode. Radio frequency extracted power was 0.1-4 MW, with pulselengths of 80-500 ns. Experimental results suggest the possibility of competition with the TE₂₁ backward wave mode. Frequency spectrum measurements have shown a wide content of frequencies during the voltage pulse, an undesirable result for use in narrow-band devices     

Eccentricity of the electron beam in a gyrotron cavity

Dependence of the coupling of the electron beam and RF field in a gyrotron cavity on eccentricity of the electron beam is studied.     

Experimental studies of gyrotron electron beam systems

In order to provide electron beams of powerful gyrotrons, magnetron-injection guns operating in the regime of the temperature limited current are used. The electron beam quality and gyrotron performances are defined both by the cathode emission processes and the processes occurring in the electron beam during its formation and transportation. The results of measurements of the energy spectrum and velocity spread of the gyrotron electron beam in different regimes are given. Experimental data on the parameter of efficient emission inhomogeneity for different regimes are presented, as well as the dependencies of electron beam parameters on efficient inhomogeneity of the cathode     

Space charge effects in a gyrotron employing a solid electron beam

The influence of space charge forces on the performance of a single cacity gyrotron oscillator which uses a solid electron beam was investigated. It was found that space charge effects cause a large efficiency degradation as the beam current is increased, if the other experimental parameters are unchanged. A small increase in the magnetic field, however, can restore the efficiency to higher values.This research was supported by the U.S. Office of Naval Research.     

大回旋cusp电子注数值模拟

新一代宽带、高增益、大功率回旋行波管需要新型的电子注,而大回旋cusp电子注为其实现提供了可能。对大回旋cusp电子注进行系统理论分析,建立了大回旋cusp电子注的物理模型,在理论分析基础上进行了大量数值计算和模拟优化,并对大回旋cusp电子枪设计中的影响因素进行探讨。设计出一支低速度零散、高速度比、低纹波,适用于高次谐波的高功率(54 kV, 2.7 A)cusp电子枪。     

大回旋cusp电子注数值模拟

 新一代宽带、高增益、大功率回旋行波管需要新型的电子注,而大回旋cusp电子注为其实现提供了可能。对大回旋cusp电子注进行系统理论分析,建立了大回旋cusp电子注的物理模型,在理论分析基础上进行了大量数值计算和模拟优化,并对大回旋cusp电子枪设计中的影响因素进行探讨。设计出一支低速度零散、高速度比、低纹波,适用于高次谐波的高功率(54 kV, 2.7 A)cusp电子枪。     

Charged-particle acceleration by a modulated electron beam in a periodically inhomogeneous plasma

Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 33, No. 2, pp. 177–181, February, 1990.     

Spectrum of coherent transition radiation generated by a modulated electron beam

The spectrum of coherent transition radiation has been recorded with the use of a Martin–Puplett interferometer. It has been shown that the spectrum includes monochromatic lines that are caused by the modulation of an electron beam with the frequency of an accelerating radio-frequency field ν_RF and correspond to resonances at ν _k = kν_RF k ≤ 10. To determine the length of an electron bunch from the measurement of the spectrum from a single bunch, it is necessary to use a spectrometer with the resolution Δν_sp > ν_RF.     

Interaction of a modulated electron beam with a plasma

Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 32, No. 11, pp. 1351–1357, November, 1989.     

回旋电子束横纵速度比测试技术

摘要:通过对回旋电子束形成的电位和电场分布,推导出电子束横纵速度比测量的计算式.提出将电子束作传输线内导体等效,采用陶瓷电容分压器来测量速度比的方法.介绍了该测量装置的设计和加工工艺,及陶瓷电容分压器的标定方法和结果分析,并介绍了初步的原理性实验结果.该测试方法装置简单,测试电子束横纵速度比时不会破坏电子束的特性,能够...     

大回旋电子束双磁会切电子枪的设计

 分析了Ka波段二次谐波回旋行波管双磁会切电子枪的理论模型,计算了电子枪的设计参数;采用EGUN软件进行模拟,设计出了产生大回旋电子束的双磁会切电子枪。该枪电压为70 kV,电流为3.35 A,电子束横纵速度比为1.62,速度零散为4.2%。给出了电子束速度比、速度零散沿轴线的分布,进而讨论了阳极电压对电子束性能的影响,结果表明选择适当的阳极电压和阴极磁场对得到好的电子束参量作用明显。     

Observation of fine structure in the phase locking of a non-linear oscillator

Experimental observations of one-dimensional Poincaré maps of a periodically kicked non-linearly oscillating neon lamp are reported. The complete phase-lock behavior of this oscillator, including superstable phase locking and periodic-doubling bifurcations, could easily be understood with the help of these Poincaré maps.     

Diocotron instability of the electron beam in the drift tube of a gyrotron

A cold fluid model is used to investigate instabilities associated with a velocity shear due to the self fields of a relativistic electron beam inside the beam tunnel of a gyrotron. General statements concerning the stability of an electron beam like the frequency and the growth rate are possible. The growth is expressed as a length that can be compared with the geometry in the gun-tube-resonator system.     

Quasi-Gaussian beam from a multicore fibre laser by phase locking of supermodes

We present a new cavity design for controlling the spatial quality of the beam delivered by a fibre laser including a multicore fibre. A quasi Gaussian profile is produced at the 7-core fibre output involving self-imaging effects in the multicore fibre and spatial filtering. Numerical and experimental investigations analyse the spatial and spectral characteristics of the multicore fibre laser.     

回旋电子束横纵速度比测试技术

通过对回旋电子束形成的电位和电场分布,推导出电子束横纵速度比测量的计算式。提出将电子束作传输线内导体等效,采用陶瓷电容分压器来测量速度比的方法。介绍了该测量装置的设计和加工工艺,及陶瓷电容分压器的标定方法和结果分析,并介绍了初步的原理性实验结果。该测试方法装置简单,测试电子束横纵速度比时不会破坏电子束的特性,能够做到在回旋管运行时在线测量,实时监测电子束质量。     

Electeostatic equilibrium of a modulated electron beam in a magnetoactive plasma

The two-dimensional (axisymmetric) equilibrium of a modulated electron beam (sequence of bunches) in a magnetoactive plasma under resonance conditions, when the frequency of modulation of the beam _M is close to (less than) the plasma frequency _p, is studied. The field of the collective electrostatic wave, focusing the bunches, is compensated by the thermal repulsion of the beam electrons. Based on the solutions obtained, it is established that the external magnetic field has a twofold effect on the equilibrium beam: first, to a weakening of the radial component of the focusing field because of the appearance of anisotropy in the dielectric permittivity tensor of the plasma and, second, an additional radial focusing of the bunches when they are rotated by the Lorentz force. The regions of the beam and plasma parameters in which one or another of the indicated effects predominates are determined and the conditions for the predominance of magnetic over electrostatic focusing are found.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 3–8, March, 1985.The author thanks V. B. Krasovitskii for proposing the subject and for constant interest in this work.