共查询到20条相似文献,搜索用时 31 毫秒
1.
V. E. Zapevalov V. K. Lygin O. V. Malygin M. A. Moiseev V. I. Khizhnyak V. P. Karpov E. M. Tai T. Idehara S. Mitsudo I. Ogawa T. Saito 《Radiophysics and Quantum Electronics》2007,50(6):420-428
We consider a general concept of construction, the possible versions, and specific features of a gyrotron, whose output power
in CW oscillation regime can reach a few kilowatts at a frequency of 300 GHz. The gyrotron is designed for work in a high-frequency
facility in combination with a “dry” cryomagnet, which ensures a magnetic field of up to 12 T, required for the gyrotron operation.
The basic results of numerical simulation and optimization of the electron gun, the resonant cavity, and other subsystems
of the gyrotron are presented. The designs used for the gyrotron development are justified. Preliminary experiments showed
the efficiency of the pilotproduction gyrotron with an output power of about 2 kW, which is record-breaking in this frequency
range.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 6, pp. 461–470, June 2007. 相似文献
2.
太赫兹回旋管可实现高功率输出,并具有一定的频率调谐范围,是核磁共振波谱系统理想的高功率太赫兹辐射源。设计了263 GHz,TE5,2基波连续调谐回旋管,通过磁场调节实现频率调谐范围为1.39 GHz,利用时域多模多频自洽非线性理论对设计的连续调谐回旋管非稳定振荡状态进行了研究。结果表明,在低次纵向谐波模式工作磁场范围内,当工作电流大于起振电流时,连续调谐回旋管先进入稳定状态,高次纵向谐波模式被抑制,工作模式TE5,2的输出功率随时间不变;当电流增大,纵向谐波模式间的竞争引起回旋管由稳定状态进入到非稳定振荡状态,工作模式TE5,2的输出功率随时间呈振荡变化且互作用效率大大降低;随着电流的进一步增大,回旋管又回到与低电流不同的稳定状态,互作用效率进一步降低。同时发现非稳定振荡状态的起始电流随着磁场增加而增大。本研究对需工作于稳定状态的面向DNP-NMR应用的连续调谐太赫兹回旋管的研制具有一定指导意义。 相似文献
3.
回旋行波管放大器是一种具有高功率、高频率、宽带宽的毫米波放大器,TE02模二次谐波回旋行波管放大器在保持基波回旋行波管放大器的基础上极大地减小了工作磁场,从而具有广阔的应用前景. 利用两段分布式损耗的互作用结构,有效抑制了绝对不稳定性和回旋返波振荡,避免了模式互作用电路引起的模式畸变,提高了输出功率,在一定程度上克服了谐波互作用较弱的缺点,满足了扩展功率容量和放大器长时间稳定工作的要求. 非线性模拟结果和粒子模型(particle in cell)模拟结果均表明,在工作电压为100k
关键词:
W波段
二次谐波
回旋行波管放大器 相似文献
4.
R. M. Rozental N. S. Ginzburg N. I. Zaitsev E. V. Ilyakov I. S. Kulagin 《Technical Physics》2006,51(1):78-81
The feasibility of controlling the spectrum of multifrequency oscillations in a gyrotron by means of external reflections
is studied. It is shown that, in self-modulation oscillation modes of operation, the radiation spectrum lines may come close
to the resonance frequencies of a combined electromagnetic system including the reflector-limited part of the output waveguide.
Under these conditions, the frequency separation of modes and, accordingly, the self-modulation period can be controlled by
varying the position of the reflector. Theoretical results are corroborated by experiments with a 30-GHz relativistic gyrotron
with an external reflector. 相似文献
5.
E. V. Kal’yanov 《Technical Physics》2008,53(7):913-918
A controllable self-oscillating system with self-switching that includes additional feedback in an oscillator consisting of
a nonlinear amplifier, first-order and second-order filters, and a delay line configured into a closed loop is proposed. A
mathematical model of the system and results of its numerical analysis are presented. It is shown that, in a system with time
lag and a large inertia parameter, oscillation may become chaotic even if only regular oscillation takes place in the absence
of self-switching. The effect of additional feedback on an oscillator-containing system without an inertia element, second-order
filter, or delay line is considered. 相似文献
6.
Muggli P. Tran M.Q. Tran T.M. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1992,20(4):458-465
The parasitic oscillation of the TE°21 gyrotron backward-wave (gyro BW) mode is observed in a low-Q , 8 GHz TE°011, gyrotron. At low power (P BW<5 kW), the oscillation of the gyro BW mode, simultaneously with the gyrotron mode, results in a maximum TE°011, mode efficiency of less than 0.25. The parasitic oscillation is suppressed by operating the gyrotron with a negative magnetic field gradient along the electron beam, which allows the maximum efficiency to reach 0.40 and the output power to be multiplied by a factor varying from 1.4 to 1.7. The optimum efficiency curve of the TE°011 mode indicates that the low-Q cavity behaves as a much higher Q diff cavity. Excessive values of magnetic field gradient and α favor the TE°012 , longitudinal mode, which oscillates in place of the TE°011 mode and limits its maximum output power. This competitive process is responsible for the high-Q -like behavior of the optimum efficiency curve 相似文献
7.
For relaxation oscillators stochastic and chaotic dynamics are investigated. The effect of random perturbations upon the period is computed. For an extended system with additional state variables chaotic behavior can be expected. As an example, the Van der Pol oscillator is changed into a third-order system admitting period doubling and chaos in a certain parameter range. The distinction between chaotic oscillation and oscillation with noise is explored. Return maps, power spectra, and Lyapunov exponents are analyzed for that purpose. 相似文献
8.
Torrezan AC Han ST Mastovsky I Shapiro MA Sirigiri JR Temkin RJ Barnes AB Griffin RG 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》2010,38(6):1150-1160
The design, operation, and characterization of a continuous-wave (CW) tunable second-harmonic 460-GHz gyrotron are reported. The gyrotron is intended to be used as a submillimeter-wave source for 700-MHz nuclear magnetic resonance experiments with sensitivity enhanced by dynamic nuclear polarization. The gyrotron operates in the whispering-gallery mode TE(11,2) and has generated 16 W of output power with a 13-kV 100-mA electron beam. The start oscillation current measured over a range of magnetic field values is in good agreement with theoretical start currents obtained from linear theory for successive high-order axial modes TE(11,2,q). The minimum start current is 27 mA. Power and frequency tuning measurements as a function of the electron cyclotron frequency have also been carried out. A smooth frequency tuning range of 1 GHz was obtained for the operating second-harmonic mode either by magnetic field tuning or beam voltage tuning. Long-term CW operation was evaluated during an uninterrupted period of 48 h, where the gyrotron output power and frequency were kept stable to within ±0.7% and ±6 ppm, respectively, by a computerized control system. Proper operation of an internal quasi-optical mode converter implemented to transform the operating whispering-gallery mode to a Gaussian-like beam was also verified. Based on the images of the gyrotron output beam taken with a pyroelectric camera, the Gaussian-like mode content of the output beam was computed to be 92% with an ellipticity of 12%. 相似文献
9.
We present the results of numerical simulation and experimental studies of the systems of forming helical electron beams with
different topologies for a 1-MW gyrotron with step frequency tuning in the range 100–170 GHz. We analyze variations in the
beam parameters including the distribution of electrons over the oscillatory velocities, as functions of the beam current
for various accelerating voltages and magnetic fields. The results of experimental studies of a prototype of the multifrequency
gyrotron in the oscillation regime such that the designed optimized electron-optical system forms an intense helical electron
beam with specified parameters in a wide interval of magnetic fields are shown.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 50, No. 9, pp. 773–784, September 2007. 相似文献
10.
V. A. Rakityansky K. A. Lukin 《International Journal of Infrared and Millimeter Waves》1995,16(6):1037-1049
In the paper the characteristic properties of the chaotic oscillation excitation in millimeter Backward-Wave Oscillators are investigated. To enhance the interaction efficiency and provide the strong nonlinear working regimes of the oscillator the weak-resonant oscillatory system with large electrical length is proposed to use. It is shown, that in this case the oscillation automodulation with complicated power spectrum are developed for the smaller values of the working current to starting current ratio in comparison with BWO having matched oscillatory system. This allows to oscillate with high efficiency the continuous millimeter chaotic (noise) signals which have a wide enough power spectrum and integral power of about several watts. 相似文献
11.
Lin A.T. Yang Z.H. Chu K.R. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1988,16(2):129-134
A self consistent and time-dependent particle code has been developed to simulate the beam-wave dynamics in a gyrotron oscillator. The code is first applied to investigate the effect of the self-consistent field profile on the scaling of the cavity-filling rate with beam current. The fixed-field theory predicts that the transient-wave growth rate depends linearly on the beam current. The simulation results agree with the theoretical prediction at low beam currents. As the beam current increases, the modified field profile changes the nature of the gain scaling from linear to nonlinear. At higher beam currents, the excited wave is observed to exhibit the behavior of the modulated oscillation, due to unequal couplings to the forward- and backward-going waves by the beam. Associated with such amplitude modulation is a periodic variation of the self-consistent field profile. At still higher beam currents, the system becomes chaotic, showing the effect of periodic doubling. Simulation results are presented for the efficiency, the self-consistent field profile, and the scaling of the transient growth rate with the beam current 相似文献
12.
S. N. Spark A. D. R. Phelps P. R. Winning 《International Journal of Infrared and Millimeter Waves》1991,12(8):885-894
The extended frequency tuning range of the Strathclyde University gyrotron is demonstrated. The gyrotron consisted of a field-immersed, field emission cold cathode and a shaped anode cavity. The cavity was oversized with an ill-defined boundary at one end. This system could therefore support the oscillation of a very large number of TEpqs modes. The maser was thus highly tunable via differential mode excitation. A heterodyne technique was used to demonstrate the maser oscillation in the Ka-band (26.5–40GHz), with the maser oscillating at 35GHz in the TE01 mode. Previous to this a quasi-optical diffraction grating spectrometer was used to show the maser was oscillating under different conditions respectively, single and multi-mode in the W-band (75–110GHz) and multi-mode in the G-band (140–220GHz). To control the output beam a quasi-optical mode converter has been successfully developed. This converts various TEpq modes into a Gaussian beam. Studying the output of the maser, the mm-wave pulse has been shown to consist of a 100ns envelope containing 2ns pulses spaced 5ns apart. Although this behaviour may have several explanations, some of the most recent code simulations predict this behaviour as a result of mode beating in the complex transient start-up of the maser oscillation. Since this gyrotron not only supports many transverse modes, but also several longitudinal modes, such beating is a likely consequence. 相似文献
13.
Wang J.G. Gilgenbach R.M. Choi J.J. Outten C.A. Spencer T.A. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1989,17(6):906-908
The authors report experimental observations of high-power microwave emission from both the high-frequency cyclotron autoresonance maser (CARM) oscillation and the low-frequency gyrotron interaction. High-power (3-10 MW) microwave emission is attributed to the CARM mechanism, which is magnetically tunable through discrete axial cavity modes from 15 through 16.7 GHz. For the same experimental parameters, megawatt-level microwave emission is observed, which is magnetically tunable from 10 through 14 GHz, indicating low-frequency gyrotron oscillation. High-frequency microwave pulse-lengths of up to 0.2 μs have been generated, which is a factor of five greater than those achieved in previous CARM experiments 相似文献
14.
T. Saito T. Nakano H. Hoshizuki K. Sakai Y. Tatematsu S. Mitsudo I. Ogawa T. Idehara V. E. Zapevalov 《International Journal of Infrared and Millimeter Waves》2007,28(12):1063-1078
A 300 GHz CW gyrotron FU CW I has been developed and installed in the Research Center for Development of Far-Infrared Region,
University of Fukui as a power source of a high frequency material processing system. Its performance was tested and the maximum
power of 1.75 kW / CW has been attained at the beam voltage of 15 kV and the beam current of 1A. The maximum window power
efficiency of 15.5% has been obtained at the cathode voltage slightly lower than 15 kV. This gyrotron is designed to deliver
a Gaussian beam after mode conversion from the oscillation mode TE22,8 in the cavity with a complex of an internal radiator and beam shaping mirrors. The detailed measurement with an infrared
camera has confirmed that a Gaussian beam is radiated when the magnetic field strength B
c
at the cavity is adjusted at a proper value. However, within a range of B
c
, the output power is emerged into multiple directions, which suggests simultaneous oscillation of competing cavity modes. 相似文献
15.
V. L. Bratman Yu. K. Kalynov V. N. Manuilov S. V. Samsonov 《Radiophysics and Quantum Electronics》2005,48(10-11):731-736
We develop a thermionic-emission electron-optical system forming a dense beam of electrons moving along helical trajectories round the axis of a gyrotron cavity. The maximum beam current is 4 A and the pitch-factor of electrons is 1.0 for a particle energy of 250 keV and a pulse duration of 10 µs. Using such a beam in a gyrotron operated at the third cyclotron harmonic, we obtain single-mode oscillation with a power of 10 µs in the TE3,8 and TE3,9 modes with frequencies 371 and 414 GHz, respectively. 相似文献
16.
We study the influence of some types of reflections on the oscillatory processes in a gyrotron. The oscillation stability
conditions in the presence of a reflected signal are estimated, the processes in a gyrotron with a fixed structure of the
HF field are simulated numerically, and the enrichment of the signal spectrum in the presence of reflections is studied.
Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novogorod, Russia. Translated from Izvestiya Vysshikh
Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 10, pp. 1348–1357, october 1998. 相似文献
17.
18.
The open-plus-closed loop (OPCL) method for chaotic systems with multiple strange attractors
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Based on the open-plus-closed-loop (OPCL) control method a systematic
and comprehensive controller is presented in this paper for a chaotic
system, that is, the Newton--Leipnik equation with two strange
attractors: the upper attractor (UA) and the lower attractor (LA).
Results show that the final structure of the suggested controller for
stabilization has a simple linear feedback form. To keep the
integrity of the suggested approach, the globality proof of the
basins of entrainment is also provided. In virtue of the OPCL
technique, three different kinds of chaotic controls of the system
are investigated, separately: the original control forcing the
chaotic motion to settle down to the origin from an arbitrary
position of the phase space; the chaotic intra-attractor control for
stabilizing the equilibrium points only belonging to the upper
chaotic attractor or the lower chaotic one; and the inter-attractor
control for compelling the chaotic oscillation from one basin to
another one. Both theoretical analysis and simulation results verify
the validity of the proposed means. 相似文献
19.
具有记忆功能的忆阻器是除电阻器、电容器和电感器之外的第四种基本二端电路元件. 提出了由φ-q平面上的一条三次单调上升的非线性曲线来确定的光滑磁控忆阻器,它有着斜"8"字形的类紧磁滞回线的伏安特性曲线. 采用此忆阻器和负电导构成的有源忆阻器替换蔡氏混沌电路中的蔡氏二极管,导出了一个基于忆阻器的混沌振荡电路. 此外,利用常规的运算放大器和乘法器等元器件给出了有源忆阻器的等效电路实现形式. 理论分析、数值仿真和电路仿真结果一致,均表明忆阻混沌电路的动力学行为依赖于忆阻器的初始状态,在不同初始状态下存在混沌振荡、周期振荡或稳定的汇等不同的运行轨道.
关键词:
忆阻器
混沌电路
初始状态
等效电路 相似文献
20.
利用替代数据法检验了摇摆条件下自然循环系统不规则复合型脉动的混沌特性, 并在此基础上进行混沌预测. 关联维数、最大Lyapunov指数等几何不变量计算结果表明不规则复合型脉动具有混沌特性, 但是由于计算结果受实验时间序列长度的限制和噪声的影响, 可能会出现错误的判断结果. 为了避免出现误判, 在提取流量脉动的非线性特征的同时, 需要用替代数据法进一步检验混沌特性是否来自于确定性的非线性系统. 本文用迭代的幅度调节Fourier 算法进行混沌检验, 在此基础上用加权一阶局域法进行混沌脉动的预测. 计算结果表明: 不规则复合型脉动是来自于确定性系统的混沌脉动, 加权一阶局域法对流量脉动进行混沌预测效果较好, 并提出动态预测方法.
关键词:
混沌时间序列
替代数据法
实时预测
两相流动不稳定性 相似文献